Mathematical Collections and Translations, in Two Tomes/System of the World in Four Dialogues/Dialogue 1
The First Dialogue.
INTERLOCVTORS.
Salviatus, Sagredus, and Simplicius.
SALVIATUS.
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sible: Since that it is necessary to introduce in Nature,Cœlestial substances that are inalterable, and Elementary that be alterable, are necessary in the opinion of Aristotle. substances different betwixt themselves, that is, the Cœlestial, and Elementary; that impassible and immortal, this alterable and corruptible. Which argument Aristotle handleth in his book De Cœlo, insinuating it first, by some discourses dependent on certain general assumptions, and afterwards confirming it with experiments and perticular demonstrations: following the same method, I will propound, and freely speak my judgement, submitting my self to your censure, and particularly to Simplicius, a Stout Champion and contender for the Aristotelian Doctrine.
Aristotle maketh the World perfect, because it hath the threefold demension.And the first Step of the Peripatetick arguments is that, where Aristotle proveth the integrity and perfection of the World, telling us, that it is not a simple line, nor a bare superficies, but a body adorned with Longitude, Latitude, and Profundity; and because there are no more dimensions but these three; The World having them, hath all, and having all, is to be concluded perfect. And again, that by simple length, that magnitude is constituted, which is called a Line, to which adding breadth, there is framed the Superficies, and yet further adding the altitude or profoundity, there results the Body, and after these three dimensions there is no passing farther, so that in these three the integrity, and to so speak, totality is terminated, which I might but with justice have required Aristotle to have proved to me by necessary consequences, the rather in regard he was able to do it very plainly, and speedily.
Simpl.What say you to the excellent demonstrations in the 2. 3. and 4. Texts,Aristotles demonstrations to prove the dimensions to be three and no more. after the definition of Continual? have you it not first there proved, that there is no more but three dimensions, for that those three are all things, and that they are every where? And is not this confirmed by the Doctrine and Authority of the Pythagorians,The number three celebrated amongst the Pythagorians who say that all things are determined by three, beginning, middle, and end, which is the number of All? And where leave you that reason, namely, that as it were by the law of Nature, this number is used in the sacrifices of the Gods? And why being so dictated by nature, do we atribute to those things that are three, and not to lesse, the title of all? why of two is it said both, and not all, unless they be three? And all this Doctrine you have in the second Text. Afterwards in the third, Ad pleniorem scientiam, we read that All, the Whole, and Perfect,Omne, Totum & Perfectum. are formally one and the same; and that therefore onely the Body, amongst magnitudes is perfect: because it is determined by three, which is All, and being divisible three manner of waies, it is every way divisible; but of the others, some are dividible in one manner, and some in two, because according to the number affixed, they have their division and continuity, and thus one magnitude is continuate one way,Or Solid. another two, a third, namely the Body, every way. Moreover in the fourth Text; doth he not after some other Doctrines, prove it by another demonstration? Scilicet, That no transition is made but according to some defect (and so there is a transition or passing from the line to the superficies, because the line is defective in breadth) and that it is impossible for the perfect to want any thing, it being every way so; therefore there is no transition from the Solid or Body to any other magnitude. Now think you not that by all these places he hath sufficiently proved, how that there's no going beyond the three dimensions, Length, Breadth, and Thickness, and that therefore the body or solid, which hath them all, is perfect?
Salv.To tell you true, I think not my self bound by all these reasons to grant any more but onely this, That that which hath beginning, middle, and end, may, and ought to be called perfect: But that then, because beginning, middle, and end, are Three, the number Three is a perfect number, and hath a faculty of conferring Perfection on those things that have the same, I find no inducement to grant; neither do I understand, nor believe that, for example, of feet, the number three is more perfect then four or two, nor do I conceive the number four to be any imperfection to the Elements: and that they would be more perfect if they were three. Better therefore it had been to have left these subtleties to the Rhetoricians, and to have proved his intent, by necessary demonstration; for so it behoves to do in demonstrative sciences.
Simpl.You seem to scorn these reasons, and yet it is all the Doctrine of the Pythagorians, who attribute so much to numbers; and you that be a Mathematician, and believe many opinions in the Pythagorick Philosophy, seem now to contemn their Mysteries.
Salv.That the Pythagorians had the science of numbers in high esteem, and that Plato himself admired humane understanding, Plato held that humane understanding partook of divinity, because it understood numbers.and thought that it pertook of Divinity, for that it understood the nature of numbers, I know very well, nor should I be far from being of the same opinion: But that the Mysteries for which Pythagoras and his sect, had the Science of numbers in such veneration, are the follies that abound in the mouths and writings of the vulgar,The Mystery of Pythagorick numbers fabulous. I no waies credit: but rather because I know that they, to the end admirable things might not be exposed to the contempt, and scorne of the vulgar, censured as sacrilegious, the publishing of the abstruce properties of Numbers,De Papyrio prætextato, Gellius 1. 2. 3. and incommensurable and irrational quantities, by them investigated; and divulged, that he who discovered them, was tormented in the other World: I believe that some one of them to deter the common sort, and free himself from their inquisitiveness, told them that the mysteries of numbers were those trifles, which afterwards did so spread amongst the vulgar; and this with a discretion and subtlety resembling that of the prudent young man, that to be freed from the importunity of his inquisitive Mother or Wife, I know not whether, who pressed him to impart the secrets of the Senate, contrived that story, which afterwards brought her and many other women to be derided and laught at by the same Senate.
Simpl.I will not be of the number of those who are over curious about the Pythagorick mysteries; but adhering to the point in hand; I reply, that the reasons produced by Aristotle to prove the dimensions to be no more than three, seem to me concludent, and I believe, That had there been any more evident demonstrations thereof, Aristotle would not have omitted them.
Sagr.Put in at least, if he had known, or remembred any more. But you Salviatus would do me a great pleasure to alledge unto me some arguments that may be evident, and clear enough for me to comprehend.
Salv.I will; and they shall be such as are not onely to be apprehended by you, but even by Simplicius himself: nor onely to be comprehended, but are also already known, although haply unobserved; and for the more easie understanding thereof, we will take this Pen and Ink, which I see already prepared for such occasions,A Geometrical demonstration of the triple dimension. and describe a few figures. And first we will note [Fig. 1. at the end of this Dialog.] these two points A B, and draw from the one to the other the curved lines, A C B, and A D B, and the right line A B, I demand of you which of them, in your mind, is that which determines the distance between the terms A B, & why?
Sagr.I should say the right line, and not the crooked, as well because the right is shorter, as because it is one, sole, and determinate, whereas the others are infinit, unequal, and longer; and my determination is grounded upon that, That it is one, and certain.
Salv.We have then the right line to determine the length between the two terms; let us add another right line and parallel to A B, which let be C D, [Fig. 2.] so that there is put between them a superficies, of which I desire you to assign me the breadth, therefore departing from the point A, tell me how, and which way you will go, to end in the line C D, and so to point me out the breadth comprehended between those lines; let me know whether you will terminate it according to the quantity of the curved line A E, or the right line A F, or any other.
Simpl.According to the right A F, and not according to the crooked, that being already excluded from such an use.
Sagr.But I would take neither of them, seeing the right line A F runs obliquely; But would draw a line, perpendicular to C D, for this should seem to me the shortest, and the properest of infinite that are greater, and unequal to one another, which may be produced from the term A to any other part of the opposite line C D.
Salv.Your choice, and the reason you bring for it in my judgment is most excellent; so that by this time we have proved that the first dimension is determined by a right line, the second namely the breadth with another line right also, and not onely right, but withall, at right-angles to the other that determineth the length, and thus we have the two dimensions of length and breadth, definite and certain. But were you to bound or terminate a height, as for example, how high this Roof is from the pavement, that we tread on, being that from any point in the Roof, we may draw infinite lines, both curved, and right, and all of diverse lengths to infinite points of the pavement, which of all these lines would you make use of?
Sagr.I would fasten a line to the Seeling, and with a plummet that should hang at it, would let it freely distend it self till it should reach well near to the pavement, and the length of such a thread being the streightest and shortest of all the lines, that could possibly be drawn from the same point to the pavement, I would say was the true height of this Room.
Salv.Very well, And when from the point noted in the pavement by this pendent thread (taking the pavement to be levell and not declining) you should produce two other right lines, one for the length, and the other for the breadth of the superficies of the said pavement, what angles should they make with the said thread?
Sagr.They would doubtless meet at right angles, the said lines falling perpendicular, and the pavement being very plain and levell.
Salv.Therefore if you assign any point, for the term from whence to begin your measure; and from thence do draw a right line, as the terminator of the first measure, namely of the length, it will follow of necessity, that that which is to design out the largeness or breadth, toucheth the first at right-angles, and that that which is to denote the altitude, which is the third dimension, going from the same point formeth also with the other two, not oblique but right angles, and thus by the three perpendiculars, as by three lines, one, certain, and as short as is possible, you have the three dimensions A B length, A C breadth, and A D height; and because, clear it is, that there cannot concurre any more lines in the said point, so as to make therewith right-angles, and the dimensions ought to be determined by the sole right lines, which make between themselves right-angles; therefore the dimensions are no more but three, and that which hath three hath all, and that which hath all, is divisible on all sides, and that which is so, is perfect, &c.
Simpl.And who saith that I cannot draw other lines? why may not I protract another line underneath, unto the point A, that may be perpendicular to the rest?
Salv.You can doubtless, at one and the same point, make no more than three right lines concurre, that constitute right angles between themselves.
Sagr.I see what Simplicius means, namely, that should the said DA be prolonged downward, then by that means there might be drawn two others, but they would be the same with the first three, differing onely in this, that whereas now they onely touch, then they would intersect, but not produce new dimensions.
Simpl.I will not say that this your argument may not be concludent; but yet this I say with Aristotle, that in things natural it is not alwaies necessary, to bring Mathematical demonstrations.
Sagr.Grant that it were so where such proofs cannot be had, yet if this case admit of them, why do not you use them? But it would be good we spent no more words on this particular, for I think that Salviatus will yield, both to Aristotle, and you, without farther demonstration, that the World is a body, and perfect, yea most perfect, as being the greatest work of God.
Salv.So really it is, therefore leaving the general contemplation of the whole, let us descend to the consideration of its parts, which Aristotle, in his first division, makes two, and they very different and almost contrary to one another; namely the Coelestial, and Elementary: that ingenerable, incorruptible, unalterable, unpassible, &c. and this exposed to a continual alteration, mutation, &c. Which difference, as from its original principle, he derives from the diversity of local motions, and in this method he proceeds.
Leaving the sensible, if I may so speak, and retiring into the Ideal world, he begins Architectonically to consider that nature being the principle of motion, it followeth that natural bodies be indued with local motion. Next he declares local motion to be of three kinds, namely, circular, right, and mixt of right and circular: and the two first he calleth simple, for that of all lines the circular, and right are onely simple; and here somewhat restraining himself, he defineth anew, of simple motions, one to be circular, namely that which is made about the medium, and the other namely the right, upwards, and downwards; upwards, that which moveth from the medium; downwards, that which goeth towards the medium. And from hence he infers, as he may by and necessary consequence, that all simple motions are confined to these three kinds, namely, to the medium, from the medium, and about the medium; the which corresponds saith he, with what hath been said before of a body, that it also is perfected by three things, and so is its motion. Having confirmed these motions, he proceeds saying, that of natural bodies some being simple, and some composed of them (and he calleth simple bodies those, that have a principle of motion from nature, as the Fire and Earth) it follows that simple motions belong to simple bodies, and mixt to the compound; yet in such sort, that the compounded incline to the part predominant in the composition.
Sagr.Pray you hold a little Salviatus, for I find so many doubts to spring up on all sides in this discourse, that I shall be constrained, either to communicate them if I would attentively hearken to what you shall add, or to take off my attention from the things spoken, if I would remember objections.
Salv.I will very willingly stay, for that I also run the same hazard, and am ready at every step to lose my self whilst I sail between Rocks, and boisterous Waves, that make me, as they say, to lose my Compass; therefore before I make them more, propound your difficulties.
Sagr.You and Aristotle together would at first take me a little out of the sensible World, to tell me of the Architecture, wherewith it ought to be fabricated; and very appositly begin to tell me, that a natural body is by nature moveable, nature being (as elsewhere it is defined) the principle of motion. But here I am somewhat doubtfull why Aristotle said not that of natural bodies, some are moveable by nature, and others immoveable, for that in the definition, nature is said to be the principle of Motion, and Rest; for if natural bodies have all a principle of motion, either he might have omitted the mention of Rest, in the definition of nature: or not have introduced such a definition in this place. Next, as to the declaration of what Aristotle intends by simple motions, and how by Spaces he determines them, calling those simple, that are made by simple lines, which are onely the right, and circular, I entertain it willingly; nor do I desire to tenter the instance of the Helix, about the Cylinder; which in that it is in every part like to it self, might seemingly be numbred among simple lines. But herein I cannot concurre, that he should so restrain simple motions (whilst he seems to go about to repeat the same definition in other words) as to call one of them the motion about the medium, the others Sursum & Deorsum, namely upwards and downward; which terms are not to be used, out of the World fabricated, but imply it not onely made, but already inhabited by us; for if the right motion be simple, by the simplicity of the right line, and if the simple motion be natural, it is made on every side, to wit, upwards, downwards, backwards, forwards, to the right, to the left, and if any other way can be imagined, provided it be straight, it shall agree to any simple natural body; or if not so, then the supposion of Aristotle is defective. It appears moreover that Aristotle hinteth but one circular motion alone to be in the World, and consequently but one onely Center, to which alone the motions of upwards and downwards, refer. All which are apparent proofs, that Aristotles aim is, to make white black, and to accommodate Architecture to the building, and not to modle the building according to the precepts of Arthitecture: for if I should say that Nature in Universal may have a thousand Circular Motions, and by consequence a thousand Centers, there would be also a thousand motions upwards, and downwards. Again he makes as hath been said, a simple motion, and a mixt motion, calling simple, the circular and right; and mixt, the compound of them two: of natural bodies he calls some simple (namely those that have a natural principle to simple motion) and others compound: and simple motions he attributes to simple bodies, and the compounded to the compound; but by compound motion he doth no longer understand the mixt of right and circular, which may be in the World; but introduceth a mixt motion as impossible, as it is impossible to mixe opposite motions made in the same right line, so as to produce from them a motion partly upwards, partly downwards; and, to moderate such an absurdity, and impossibility, he asserts that such mixt bodies move according to the simple part predominant: which necessitates others to say, that even the motion made by the same right line is sometimes simple, and sometimes also compound: so that the simplicity of the motion, is no longer dependent onely on the simplicity of the line.
Simpl.How? Is it not difference sufficient, that the simple and absolute are more swift than that which proceeds from predominion? and how much faster doth a piece of pure Earth descend, than a piece of Wood?
Sagr.Well, Simplicius; But put case the simplicity for this cause was changed, besides that there would be a hundred thousand mixt motions, you would not be able to determine the simple; nay farther, if the greater or lesse velocity be able to alter the simplicity of the motion, no simple body should move with a simple motion; since that in all natural right motions, the velocity is ever encreasing, and by consequence still changing the simplicity, which as it is simplicity, ought of consequence to be immutable, and that which more importeth, you charge Aristotle with another thing, that in the definition of motions compounded, he hath not made mention of tardity nor velocity, which you now insert for a necessary and essential point. Again you can draw no advantage from this rule, for that there will be amongst the mixt bodies some, (and that not a few) that will move swiftly, and others more slowly than the simple; as for example, Lead, and Wood, in comparison of earth; and therefore amongst these motions, which call you the simple, and which the mixt?
Simpl.I would call that simple motion, which is made by a simple body, and mixt, that of a compound body.
Sagr.Very well, and yet Simplicius a little before you said, that the simple, and compound motions, discovered which were mixt, and which were simple bodies; now you will have me by simple and mixt bodies, come to know which is the simple, and which is the compound motion: an excellent way to keep us ignorant, both of motions and bodies. Moreover, you have also a little above declared, how that a greater velocity did not suffice, but you seek a third condition for the definement of simple motion, for which Aristotle contented himself with one alone, namely, of the simplicity of the Space, or Medium: But now according to you, the simple motion, shall be that which is made upon a simple line, with a certain determinate velocity, by a body simply moveable. Now be it as you please, and let us return to Aristotle, who defineth the mixt motion to be that compounded of the right, and circular, but produceth not any body, which naturally moveth with such a motion.
Salv.I come again to Aristotle, who having very well, and Methodically begun his discourse, but having a greater aim to rest at, and hit a marke, predesigned in his minde, then that to which his method lead him, digressing from the purpose, he comes to assert, as a thing known and manifest, that as to the motions directly upwards or downwards, they naturally agree to Fire, and Earth; and that therefore it is necessary, that besides these bodies, which are neer unto us, there must be in nature another, to which the circular motion may agree: which shall be so much the more excellent by how much the circular motion is more perfect, then the streight, but how much more pefect that is than this, he determines from the greatness of the circular lines perfection above the right line;The circular line perfect, according to Aristotle, and but the right imperfect, and why. calling that perfect, and this imperfect; imperfect, because if infinite it wanteth a termination, and end: and if it be finite, there is yet something beyond which it may be prolonged. This is the basis, ground work, and master-stone of all the Fabrick of the Aristotelian World, upon which they superstruct all their other properties, of neither heavy nor light, of ingenerable incorruptible, exemption from all motions, some onely the local, &c. And all these passions he affirmeth to be proper to a simple body that is moved circularly; and the contrary qualities of gravity, levity, corruptibility, &c. he assigns to bodies naturally moveable in a streight line, for that if we have already discovered defects in the foundation, we may rationally question what soever may farther built thereon. I deny not, that this which Aristotle hitherto hath introduced, with a general discourse dependent upon universal primary principles, hath been since in process of time, re-inforced with particular reasons, and experiments; all which it would be necessary distinctly to consider and weigh; but because what hath been said hitherto presents to such as consider the same many and no small difficulties, (and yet it would be necessary, that the primary principles and fundamentals, were certain, firm, and established, that so they might with more confidence be built upon) it would not be amiss, before we farther multiply doubts, to see if haply (as I conjecture) betaking our selves to other waies, we may not light upon a more direct and secure method; and with better considered principles of Architecture lay our primary fundamentals. Therefore suspending for the present the method of Aristotle, (which we will re-assume again in its proper place, and particularly examine;*) I say, that in the things hitherto affirmed by him, I agree with him, and admit that the World is a body enjoying all dimensions, and therefore most perfect; and I add, that as such, it is necessarily most ordinate, that is, having parts between themselves, with exquisite and most perfect order disposed; which assumption I think is not to be denied, neither by you or any other.
Simpl.Who can deny it? the first particular (of the worlds dimensions) is taken from Aristotle himself, and its denomination of ordinate seems onely to be assumed from the order which it most exactly keeps.
Salv.This principle then established, one may immediately conclude, that if the entire parts of the World should be by their nature moveable, it is impossible that their motions should be right, or other than circular; and the reason is sufficiently easie, and manifest; for that whatsoever moveth with a right motion, changeth place; and continuing to move, doth by degrees more and more remove from the term from whence it departed, and from all the places thorow which it successively passed; and if such motion naturally suited with it, then it was not at the beginning in its proper place; and so the parts of the World were not disposed with perfect order. But we suppose them to be perfectly ordinate, therefore as such, it is impossible that they should by nature change place, and consequently move in a right motion. Again, the right motion being by nature infinite, for that the right line is infinite and indeterminate, it is impossible that any moveable can have a natural principle of moving in a right line; namely toward the place whither it is impossible to arrive, there being no prae-finite term; and nature, as Aristotle himself saith well, never attempts to do that which can never be done, nor essaies to move whither it is impossible to arrive. And if any one should yet object, that albeit the right line, and consequently the motion by it is producible in infinitum, that is to say, is interminate; yet nevertheless Nature, as one may say, arbitrarily hath assigned them some terms, and given natural instincts to its natural bodies to move unto the same; I will reply, that this might perhaps be fabled to have come to pass in the first Chaos, where indistinct matters confusedly and inordinately wandered; to regulate which, Nature very appositely made use of right motions, by which, like as the well-constituted, moving, disorder themselves, so were they which were before depravedly disposed by this motion ranged in order: but after their exquisite distribution and collocation, it is impossible that there should remain natural inclinations in them of longer moving in a right motion, from which now would ensue their removal from their proper and natural place, that is to say, their disordination; we may therefore say that the right motion serves to conduct the matter to erect the work; but once erected, that it is to rest immoveable, or if moveable, to move it self onely circularly. Unless we will say with Plato, that these mundane bodies, after they had been made and finished, were for a certain time moved by their Maker, in a right motion, but that after their attainment to certain and determinate places, they were revolved one by one in Spheres, passing from the right to the circular motion, wherein they have been ever since kept and maintained. A sublime conceipt, and worthy indeed of Plato: upon which, I remember to have heard our common friend the*Lyncean Academick discourse in this manner, if I have not forgot it. Every body for any reason constituted in a state of rest, but which is by nature moveable, being set at liberty doth move; provided withal, that it have an inclination to some particular place; for should it stand indifferently affected to all, it would remain in its rest, not having greater inducement to move one way than another. From the having of this inclination necessarily proceeds, that it in its moving shall continually increase its acceleration, and beginning with a most slow motion, it shall not acquire any degree of velocity, before it shall have passed thorow all the degrees of less velocity, or greater tardity: for passing from the state of quiet (which is the infinite degree of tardity of motion) there is no reason by which it should enter into such a determinate degree of velocity, before it shall have entred into a less, and into yet a less, before it entred into that: but rather it stands with reason, to pass first by those degrees nearest to that from which it departed, and from those to the more remote; but the degree from whence the moveable began to move, is that of extreme tardity, namely of rest. Now this acceleration of motion is never made,The moveable doth not accelerate, save only as it approaheth nearer to its term. but when the moveable in moving acquireth it; nor is its acquist other than an approaching to the place desired, to wit, whither its natural inclination attracts it, and thither it tendeth by the shortest way; namely, by a right line. We may upon good grounds therefore say, That Nature, to confer upon a moveable first constituted in rest a determinate velocity, useth to make it move according to a certain time and space with a right motion.Nature, to introduce in the moveable a certain degree of velocity, made it move in a right line. This presupposed, let us imagine God to have created the Orb v. g. of Jupiter, on which he had determined to confer such a certain velocity, which it ought afterwards to retain perpetually uniform; we may with Plato say, that he gave it at the beginning a right and accelerate motion, and that it afterwards being arrived to that intended degree of velocity,Uniform velocity convenient to the circular motion. he converted its right, into a circular motion, the velocity of which came afterwards naturally to be uniform.
Sagr.I hearken to this Discourse with great delight; and I believe the content I take therein will be greater, when you have satisfied me in a doubt: that is, (which I do not very well comprehend) how it of necessity ensues, that a moveable departing from its rest,Betwixt rest, and any assigned degree of velocity, infinite degrees of less velocity interpose. and entring into a motion to which it had a natural inclination, it passeth thorow all the precedent degrees of tardity, comprehended between any assigned degree of velocity, and the state of rest, which degrees are infinite? so that Nature was not able to confer them upon the body of Jupiter, his circular motion being instantly created with such and such velocity.
Salv.I neither did,Nature doth not immediately confer a determinate degree of velocity, howbeit she could. nor dare say, that it was impossible for God or Nature to confer that velocity which you speak of, immediately; but this I say, that de facto she did not do it; so that the doing it would be a work extra-natural, and by consequence miraculous
Sagr.Then you believe, that a stone leaving its rest, and entring into its natural motion towards the centre of the Earth, passeth thorow all the degrees of tardity inferiour to any degree of velocity?
Salv.I do believe it, nay am certain of it; and so certain, that I am able to make you also very well satisfied with the truth thereof.
Sagr.Though by all this daies discourse I should gain no more but such a knowledge, I should think my time very well bestowed.
Salv.By what I collect from our discourse, a great part of your scruple lieth in that it should in a time, and that very short, pass thorow those infinite degrees of tardity precedent to any velocity, acquired by the moveable in that time: and therefore before we go any farther, I will seek to remove this difficulty, which shall be an easie task; for I reply, that the moveable passeth by the aforesaid degrees,The moveable departing from rest passeth thorow all degrees of velocity without staying in any. but the passage is made without staying in any of them; so that the passage requiring but one sole instant of time, and every small time containing infinite instants, we shall not want enough of them to assign its own to each of the infinite degrees of tardity; although the time were never so short.
Sagr.Hither to I apprehend you; nevertheless it is very much that that Ball shot from a Cannon (for such I conceive the cadent moveable) which yet we see to fall with such a precipice, that in less than ten pulses it will pass two hundred yards of altitude; should in its motion be found conjoyned with so small a degree of velocity, that, should it have continued to have moved at that rate without farther acceleration, it would not have past the same in a day.
Salv.You may say, nor yet in a year, nor in ten, no nor in a thousand; as I will endeavour to shew you, and also happily without your contradiction, to some sufficiently simple questions that I will propound to you. Therefore tell me if you make any question of granting that, that that ball in descending goeth increasing its impetus and velocity.
Sagr.I am most certain it doth.
Salv.And if I should say that the impetus acquired in any place of its motion, is so much, that it would suffice to re-carry it to that place from which it came, would you grant it?
Sagr.I should consent to it without contradiction, provided alwaies, that it might imploy without impediment its whole impetus in that sole work of re-conducting it self, or another equal to it, to that self-same height as it would do,The ponderous mover descending acquireth impetus sufficient to re-carry it to the like height. in case the Earth were bored thorow the centre, and the Bullet fell a thousand yards from the said centre, for I verily believe it would pass beyond the centre, ascending as much as it had descended; and this I see plainly in the experiment of a plummet hanging at a line, which removed from the perpendicular, which is its state of rest, and afterwards let go, falleth towards the said perpendicular, and goes as far beyond it; or onely so much less, as the opposition of the air, and line, or other accidents have hindred it. The like I see in the water, which descending thorow a pipe, re-mounts as much as it had descended.
Salv.You argue very well. And for that I know you will not scruple to grant that the acquist of the impetus is by means of the receding from the term whence the moveable departed, and its approach to the centre, whither it motion tendeth; will you stick to yeeld, that two equal moveables, though descending by divers lines, without any impediment, acquire equal impetus, provided that the approaches to the centre be equal?
Sagr.I do not very well understand the question.
Salv.I will express it better by drawing a Figure: therefore I will suppose the line A B [in Fig. 3.] parallel to the Horizon, and upon the point B, I will erect a perpendicular B C; and after that I adde this slaunt line C A. Understanding now the line C A to be an inclining plain exquisitely polished, and hard, upon which descendeth a ball perfectly round and of very hard matter, and such another I suppose freely to descend by the perpendicular C B: will you now confess that the impetus of that which descends by the plain C A, being arrived to the point A, may be equal to the impetus acquired by the other in the point B, after the descent by the perpendicular C B?
Sagr.I resolutely believe so:The impetuosity of moveables equally approaching to the centre, are equal. for in effect they have both the same proximity to the centre, and by that, which I have already granted, their impetuosities would be equally sufficient to re-carry them to the same height.
Salv.Tell me now what you believe the same ball would do put upon the Horizontal plane A B?
Sagr.It would lie still,Upon an horizontal plane the moveable lieth still. the said plane having no declination.
Salv.But on the inclining plane C A it would descend, but with a gentler motion than by the perpendicular C B?
Sagr.I may confidently answer in the affirmative, it seeming to me necessary that the motion by the perpendicular C B should be more swift, than by the inclining plane CA; yet nevertheless, if this be, how can the Cadent by the inclination arrived to the point A, have as much impetus, that is, the same degree of velocity, that the Cadent by the perpendicular shall have in the point B? these two Propositions seem contradictory.
Salv.Then you would think it much more false,The velocity by the inclining plane equal to the velocity by the perpendicular, and the motion by the perpendicular swifter than by the inclination. should I say, that the velocity of the Cadents by the perpendicular, and inclination, are absolutely equal: and yet this is a Proposition most true, as is also this that the Cadent moveth more swiftly by the perpendicular, than by the inclination.
Sagr.These Propositions to my ears sound very harsh: and I believe to yours Simplicius?
Simpl.I have the same sense of them.
Salv.I conceit you jest with me, pretending not to comprehend what you know better than my self: therefore tell me Simplicius, when you imagine a moveable more swift than another, what conceit do you fancy in your mind?
Simpl.I fancie one to pass in the same time a greater space than the other, or to move equal spaces, but in lesser time.
Salv.Very well: and for moveables equally swift, what's your conceit of them?
Simpl.I fancie that they pass equal spaces in equal times.
Salv.And have you no other conceit thereof than this?
Simpl.This I think to be the proper definition of equal motions.
Sagr.We will add moreover this other:Velocities are said to be equal, when the spaces passed are proportionate to their time. and call that equal velocity, when the spaces passed have the same proportion, as the times wherein they are past, and it is a more universal definition.
Salv.It is so: for it comprehendeth the equal spaces past in equal times, and also the unequal past in times unequal, but proportionate to those spaces. Take now the same Figure, and applying the conceipt that you had of the more hastie motion, tell me why you think the velocity of the Cadent by C B, is greater than the velocity of the Descendent by C A?
Simpl.I think so; because in the same time that the Cadent shall pass all C B, the Descendent shall pass in C A, a part less than C B.
Salv.True; and thus it is proved, that the moveable moves more swiftly by the perpendicular, than by the inclination. Now consider, if in this same Figure one may any way evince the other conceipt, and finde that the moveables were equally swift by both the lines C A and C B.
Simpl.I see no such thing; nay rather it seems to contradict what was said before.
Salv.And what say you, Sagredus? I would not teach you what you knew before, and that of which but just now you produced me the definition.
Sagr.The definition I gave you, was, that moveables may be called equally swift, when the spaces passed are proportional to the times in which they passed; therefore to apply the definition to the present case, it will be requisite, that the time of descent by C A, to the time of falling by C B, should have the same proportion that the line C A hath to the line C B; but I understand not how that can be, for that the motion by C B is swifter than by C A.
Salv.And yet you must of necessity know it. Tell me a little, do not these motions go continually accelerating?
Sagr.They do; but more in the perpendicular than in the inclination.
Salv.But this acceleration in the perpendicular, is it yet notwithstanding such in comparison of that of the inclined, that two equal parts being taken in any place of the said perpendicular and inclining lines, the motion in the parts of the perpendicular is alwaies more swift, than in the part of the inclination?
Sagr.I say not so: but I could take a space in the inclination, in which the velocity shall be far greater than in the like space taken in the perpendicular; and this shall be, if the space in the perpendicular should be taken near to the end C, and in the inclination, far from it.
Salv.You see then, that the Proposition which saith, that the motion by the perpendicular is more swift than by the inclination, holds not true universally, but onely of the motions, which begin from the extremity, namely from the point of rest: without which restriction, the Proposition would be so deficient, that its very direct contrary might be true; namely, that the motion in the inclining plane is swifter than in the perpendicular: for it is certain, that in the said inclination, we may take a space past by the moveable in less time, than the like space past in the perpendicular. Now because the motion in the inclination is in some places more, in some less, than in the perpendicular; therefore in some places of the inclination, the time of motion of the moveable, shall have a greater proportion to the time of the motion of the moveable, by some places of the perpendicular, than the space passed, to the space passed: and in other places, the proportion of the time to the time, shall be less than that of the space to the space. As for example: two moveables departing from their quiescence, namely, from the point C, one by the perpendicular C B, [in Fig. 4.] and the other by the inclination C A, in the time that, in the perpendicular, the moveable shall have past all C B, the other shall have past C T lesser. And therefore the time by C T, to the time by C B (which is equal) shall have a greater proportion than the line C T to C B, being that the same to the less, hath a greater proportion than to the greater. And on the contrary, if in C A, prolonged as much as is requisite, one should take a part equal to C B, but past in a shorter time; the time in the inclination shall have a less proportion to the time in the perpendicular, than the space to the space. If therefore in the inclination and perpendicular, we may suppose such spaces and velocities, that the proportion between the said spaces be greater and less than the proportion of the times; we may easily grant, that there are also spaces, by which the times of the motions retain the same proportion as the spaces.
Sagr.I am already freed from my greatest doubt, and conceive that to be not onely possible, but necessary, which I but now thought a contradiction: but nevertheless I understand not as yet, that this whereof we now are speaking, is one of these possible or necessary cases; so as that it should be true, that the time of descent by C A, to the time of the fall by C B, hath the same proportion that the line C A hath to C B; whence it may without contradiction be affirmed, that the velocity by the inclination C A, and by the perpendicular C B, are equal.
Salv.Content your self for this time, that I have removed your incredulity; but for the knowledge of this, expect it at some other time, namely, when you shall see the matters concerning local motion demonstrated by our Academick; at which time you shall find it proved, that in the time that the one moveable falls all the space C B, the other descendeth by C A as far as the point T, in which falls the perpendicular drawn from the point B: and to find where the same Cadent by the perpendicular would be when the other arriveth at the point A, draw from A the perpendicular unto C A, continuing it, and C B unto the interfection, and that shall be the point sought. Whereby you see how it is true, that the motion by C B is swifter than by the inclination C A (supposing the term C for the beginning of the motions compared) because the line C B is greater than C T, and the other from C unto the intersection of the perpendicular drawn from A, unto the line C A, is greater than C A, and therefore the motion by it is swifter than by C A. But when we compare the motion made by all C A, not with all the motion made in the same time by the perpendicular continued, but with that made in part of the time, by the sole part C B, it hinders not, that the motion by C A, continuing to descend beyond, may arrive to A in such a time as is in proportion to the other time, as the line C A is to the line C B. Now returning to our first purpose; which was to shew, that the grave moveable leaving its quiescence, passeth descending by all the degrees of tardity, precedent to any whatsoever degree of velocity that it acquireth, re-assuming the same Figure which we used before, let us remember that we did agree, that the Descendent by the inclination C A, and the Cadent by the perpendicular C B, were found to have acquired equal degrees of velocity in the terms B and A: now to proceed, I suppose you will not scruple to grant, that upon another plane less steep than A C; as for example, A D [in Fig. 5.] the motion of the descendent would be yet more flow than in the plane A C. So that it is not any whit dubitable, but that there may be planes so little elevated above the Horizon A B, that the moveable, namely the same ball, in any the longest time may reach the point A, which being to move by the plane A B, an infinite time would not suffice: and the motion is made always more slowly, by how much the declination is less. It must be therefore confest, that there may be a point taken upon the term B, so near to the said B, that drawing from thence to the point A a plane, the ball would not pass it in a whole year. It is requisite next for you to know, that the impetus, namely the degree of velocity the ball is found to have acquired when it arriveth at the point A, is such, that should it continue to move with this self-same degree uniformly, that is to say, without accelerating or retarding; in as much more time as it was in coming by the inclining plane, it would pass double the space of the plane inclined: namely (for example) if the ball had past the plane D A in an hour, continuing to move uniformly with that degree of velocity which it is found to have in its arriving at the term A, it shall pass in an hour a space double the length D A; and because (as we have said) the degrees of velocity acquired in the points B and A, by the moveables that depart from any point taken in the perpendicular C B, and that descend, the one by the inclined plane, the other by the said perpendicular, are always equal: therefore the cadent by the perpendicular may depart from a term so near to B, that the degree of velocity acquired in B, would not suffice (still maintaining the same) to conduct the moveable by a space double the length of the plane inclined in a year, nor in ten, no nor in a hundred. We may therefore conclude, that if it be true, that according to the ordinary course of nature a moveable, all external and accidental impediments removed, moves upon an inclining plane with greater and greater tardity, according as the inclination shall be less; so that in the end the tardity comes to be infinite, which is, when the inclination concludeth in, and joyneth to the horizontal plane; and if it be true likewise, that the degree of velocity acquired in some point of the inclined plane, is equal to that degree of velocity which is found to be in the moveable that descends by the perpendicular, in the point cut by a parallel to the Horizon, which passeth by that point of the inclining plane; it must of necessity be granted, that the cadent departing from rest, passeth thorow all the infinite degrees of tardity, and that consequently, to acquire a determinate degree of velocity, it is necessary that it move first by right lines, descending by a short or long space, according as the velocity to be acquired, ought to be either less or greater, and according as the plane on which it descendeth is more or less inclined; so that a plane may be given with so small inclination, that to acquire in it the assigned degree of velocity, it must first move in a very great space, and take a very long time; whereupon in the horizontal plane, any how little soever velocity, would never be naturally acquired, since that the moveable in this case will never move: but the motion by the horizontal line,The circular motion is never acquired naturally, without right motion precede it.
Circular motion perpetually uniform. which is neither declined or inclined, is a circular motion about the centre: therefore the circular motion is never acquired naturally, without the right motion precede it; but being once acquired, it will continue perpetually with uniform velocity. I could with other discourses evince and demonstrate the same truth, but I will not by so great a digression interrupt our principal argument: but rather will return to it upon some other occasion; especially since we not assumed the same, not to serve for a necessary demonstration, but to adorn a Platonick Conceit; to which I will add another particular observation of our Academick, which hath in it something of admirable. Let us suppose amongst the decrees of the divine Architect, a purpose of creating in the World these Globes, which we behold continually moving round, and of assigning the centre of their conversions; and that in it he had placed the Sun immoveable, and had afterwards made all the said Globes in the same place, and with the intended inclinations of moving towards the Centre, till they had acquired those degrees of velocity, which at first seemed good to the same Divine Minde; the which being acquired, we lastly suppose that they were turned round, each in his Sphere retaining the said acquired velocity: it is now demanded, in what altitude and distance from the Sun the place was where the said Orbs were primarily created; and whether it be possible that they might all be created in the same place? To make this investigation, we must take from the most skilfull Astronomers the magnitude of the Spheres in which the Planets revolve, and likewise the time of their revolutions: from which two cognitions is gathered how much (for example) Jupiter is swifter than Saturne; and being found (as indeed it is) that Jupiter moves more swiftly, it is requisite, that departing from the same altitude, Jupiter be descended more than Saturne, as we really know it is, its Orbe being inferiour to that of Saturne. But by proceeding forwards, from the proportions of the two velocities of Jupiter and Saturne, and from the distance between their Orbs, and from the proportion of acceleration of natural motion, one may finde in what altitude and distance from the centre of their revolutions,The magnitude of the Orbs, and the velocity of the motion of the Planets, answer proportionably, as if descended from the same place. was the place from whence they first departed. This found out, and agreed upon, it is to be sought, whether Mars descending from thence to his Orb, the magnitude of the Orb, and the velocity of the motion, agree with that which is found by calculation; and let the like be done of the Earth, of Venus, and of Mercury; the greatness of which Spheres, and the velocity of their motions, agree so nearly to what computation gives, that it is very admirable.
Sagr.I have hearkened to this conceit with extreme delight; and, but that I believe the making of these calculations truly would be a long and painfull task, and perhaps too hard for me to comprehend, I would make a trial of them.
Salv.The operation indeed is long and difficult; nor could I be certain to finde it so readily; therefore we shall refer it to another time, and for the present we will return to our first proposal, going on there where we made digression; which, if I well remember, was about the proving the motion by a right line of no use, in the ordinate parts of the World; and we did proceed to say, that it was not so in circular motions, of which that which is made by the moveable in it self,Finite and terminate circular motions disorder not the parts of the World. still retains it in the same place, and that which carrieth the moveable by the circumference of a circle about its fixed centre, neither puts it self, nor those about it in disorder; for that such a motion primarily is finite and terminate (though not yet finished and determined) but there is no point in the circumference,In the circular motion, every point in the circumference is the begining and end. that is not the first and last term in the circulation; and continuing it in the circumference assigned it, it leaveth all the rest, within and without that, free for the use of others, without ever impeding or disordering them. This being a motion that makes the moveable continually leave, and continually arrive at the end;Circular motion onely is uniform. it alone therefore can primarily be uniform; for that acceleration of motion is made in the moveable, when it goeth towards the term, to which it hath inclination; and the retardation happens by the repugnance that it hath to leave and part from the same term; and because in circular motion, the moveable continually leaves the natural term, and continually moveth towards the same, therefor, in it, the repugnance and inclination are always of equal force: from which equality results a velocity, neither retarded nor accelerated, i.e. an uniformity in motion. From this conformity, and from the being terminate,Circular motion may be continued perpetually. may follow the perpetual continuation by successively reiterating the circulations; which in an undeterminated line, and in a motion continually retarded or accelerated, cannot naturally be.Right motion cannot naturally be perpetual. I say, naturally; because the right motion which is retarded, is the violent, which cannot be perpetual; and the accelerate arriveth necessarily at the term, if one there be; and if there be none, it cannot be moved to it, because nature moves not whether it is impossible to attain. I conclude therefore, that the circular motion can onely naturally consist with natural bodies, parts of the universe, and constituted in an excellent disposure; and that the right, at the most that can be said for it, is assigned by nature to its bodies,Right motion assigned to natural bodies, to reduce them to perfect order, when removed from their places. and their parts, at such time as they shall be out of their proper places, constituted in a depraved disposition, and for that cause needing to be redurcd by the shortest way to their natural state. Hence, me thinks, it may rationally be concluded, that for maintenance of perfect order amongst the parts of the World, it is necessary to say, that moveables are moveable onely circularly; and if there be any that move not circularly,Rest onely, and circular motion are apt to conserve order. these of necessity are immoveable: there being nothing but rest and circular motion apt to the conservation of order. And I do not a little wonder with my self, that Aristotle, who held that the Terrestrial globe was placed in the centre of the World, and there remained immoveable, should not say, that of natural bodies some are moveable by nature, and others immoveable; especially having before defined Nature, to be the principle of Motion and Rest.
Simpl.Aristotle, though of a very perspicacious wit, would not strain it further than needed:Sensible experiments are to be preferred before humane argumentations. holding in all his argumentations, that sensible experiments were to be preferred before any reasons founded upon strength of wit, and said those which should deny the testimony of sense deserved to be punished with the loss of that sense;He who denies sense, deserves to be deprived of it. Sense sheweth that things grave move to the medium, and the light to the concave. now who is so blind, that sees not the parts of the Earth and Water to move, as being grave, naturally downwards, namely; towards the centre of the Universe, assigned by nature her self for the end and term of right motion deorsùm; and doth not likewise see the Fire and Air to move right upwards towards the Concave of the Lunar Orb, as to the natural end of motion sursùm? And this being so manifestly seen, and we being certain, that eadem est ratio totius & partium, why may we not assert it for a true and manifest proposition, that the natural motion of the Earth is the right motion ad medium, and that of the Fire, the right à medio?
Salv.The most that you can pretend from this your Discourse, were it granted to be true, is that, like as the parts of the Earth removed from the whole, namely, from the place where they naturally rest, that is in short reduced to a depraved and disordered disposure, return to their place spontaneously, and therefore naturally in a right motion, (it being granted, that eadem sit ratio totius & partium) so it may be inferred, that the Terrestrial Globe removed violently from the place assigned it by nature,It is questionable whether descending weights move in a right line. it would return by a right line. This, as I have said, is the most that can be granted you, and that onely for want of examination; but he that shall with exactness revise these things, will first deny, that the parts of the Earth, in returning to its whole, move in a right line, and not by a circular or mixt; and really you would have enough to do to demonstrate the contrary, as you shall plainly see in the answers to the particular reasons and experiments alledged by Ptolomey and Aristotle. Secondly, If another should say that the parts of the Earth, go not in their motion towards the Centre of the World, but to unite with its Whole, and that for that reason they naturally incline towards the centre of the Terrestrial Globe, by which inclination they conspire to form and preserve it, what other All, or what other Centre would you find for the World,The Earth sperical by the conspiration of its parts to its Centre. to which the whole Terrene Globe, being thence removed, would seek to return, that so the reason of the Whole might be like to that of its parts? It may be added, That neither Aristotle, nor you can ever prove, that the Earth de facto is in the centre of the Universe; but if any Centre may be assigned to the Universe,The Sun more probably in the centre of the Vniverse, than the Earth. we shall rather find the Sun placed in it, as by the sequel you shall understand.
Now, like as from the consentaneous conspiration of all the parts of the Earth to form its whole, doth follow, that they with equal inclination concurr thither from all parts;Natural inclination of the parts of all the globes of the World to go to their centre. and to unite themselves as much as is possible together, they there spherically adapt themselves; why may we not believe that the Sun, Moon, and other mundane Bodies, be also of a round figure, not by other than a concordant instinct, and natural concourse of all the parts composing them? Of which, if any, at any time, by any violence were separated from the whole, is it not reasonable to think, that they would spontaneously and by natural instinct return? and in this manner to infer, that the right motion agreeth with all mundane bodies alike.
Simpl.Certainly, if you in this manner deny not onely the Principles of Sciences, but manifest Experience, and the Senses themselves, you can never be convinced or removed from any opinion which you once conceit, therefore I will choose rather to be silent (for, contra negantes principia non est disputandum) than contend with you. And insisting on the things alledged by you even now (since you question so much as whether grave moveables have a right motion or no) how can you ever rationally deny,The right motion of grave bodies manifest to sense. that the parts of the Earth; or, if you will, that ponderous matters descend towards the Centre, with a right motion; whenas, if from a very high Tower, whose walls are very upright and perpendicular, you let them fall, they shall descend gliding and sliding by the Tower to the Earth, exactly in that very place where a plummet would fall, being hanged by a line fastned above, just there, whence the said weights were let fall? is not this a more than evident argument of the motions being right, and towards the Centre?Arguments of Aristotle, to prove that grave bodies move with an inclination to arrive at the centre of the Vniverse. In the second place you call in doubt, whether the parts of the Earth are moved, as Aristotle affirms, towards the Centre of the World; as if he had not rationally demonstrated it by contrary motions, whilst he thus argueth; The motion of heavie bodies is contrary to that of the light: but the motion of the light is manifest to be directly upwards, namely, towards the circumference of the World, therefore the motion of the heavie is directly towards the Centre of the World: and it happens per accidens,Heavie bodies move towards the centre of the Earth per accidens. that it be towards the centre of the Earth, for that this striveth to be united to that. The seeking in the next place, what a part of the Globe of the Sun or Moon would do, were it separated from its whole, is vanity; because that thereby that is sought,To seek what would follow upon an impossibility, is folly. which would be the consequence of an impossibility; in regard that, as Aristotle also demonstrates, the cœlestial bodies are impassible, impenetrable, and infrangible; so that such Page 23 a case can never happen:Cœlestial bodies neither heavie nor light, according to Aristotle. and though it should, and that the separated part should return to its whole, it would not return as grave or light, for that the same Aristotle proveth, that the Cœlestial Bodies are neither heavie nor light.
Salv.With what reason I doubt, whether grave bodies move by a right and perpendicular line, you shall hear, as I said before, when I shall examine this particular argument. Touching the second point, I wonder that you should need to discover the Paralogism of Aristotle, being of it self so manifest; and that you perceive not, that Aristotle supposeth that which is in question: therefore take notice.
Simpl.Pray Salviatus speak with more respect of Aristotle: for who can you ever perswade, that he who was the first, only, and admirable explainer of the Syllogistick forms of demonstration,Aristotle cannot equivocate, being the inventer of Logick. of Elenchs, of the manner of discovering Sophisms, Paralogisms, and in short, of all the parts of Logick, should afterwards so notoriously equivocate in imposing that for known, which is in question? It would be better, my Masters, first perfectly to understand him, and then to try, if you have a minde, to oppose him.
Salv.Simplicius, we are here familiarly discoursing among our selves, to investigate some truth; I shall not be displeased that you discover my errors; and if I do not follow the mind of Aristotle, freely reprehend me, and I shall take it in good part. Onely give me leave to expound my doubts, and to reply something to your last words, telling you, that Logick, as it is well understood, is the Organe with which we philosophate; but as it may be possible, that an Artist may be excellent in making Organs, but unlearned in playing on them, thus he might be a great Logician, but unexpert in making use of Logick; like as we have many that theorically understand the whole Art of Poetry, and yet are unfortunate in composing but meer four Verses; others enjoy all the precepts of Vinci**A famous Italian Painter., and yet know not how to paint a Stoole. The playing on the Organs is not taught by them who know how to make Organs, but by him that knows how to play on them: Poetry is learnt by continual reading of Poets: Limning is learnt by continual painting and designing: Demonstration from the reading of Books full of demonstrations, which are the Mathematical onely, and not the Logical. Now returning to our purpose, I say, that that which Aristotle seeth of the motion of light bodies, is the departing of the Fire from any part of the Superficies of the Terrestrial Globe, and directly retreating from it, mounting upwards; and this indeed is to move towards a circumference greater than that of the Earth; yea, the same Aristotle makes it to move to the concave of the Moon, but that this circumference is that of the World, or concentrick to it, so that to move towards this, is a moving towards that of the World, that he cannot affirm, unless he supposeth, That the Centre of the Earth,Paralogism of Aristotle, in proving the Earth to be in the Centre of the World. from which we see these light ascendent bodies to depart, be the same with the Centre of the World; which is as much as to say, that the terrestrial Globe is constituted in the midst of the World: which is yet that of which we were in doubt, and which Aristotle intended to prove. And do you say that this is not a manifest Paralogism?The Paralogisme of Aristotle another way discovered.
Sagr.This Argument of Aristotle appeared to me deficient also, and non-concludent for another respect; though it were granted, that that Circumference, to which the Fire directly moveth, be that which includeth the World: for that in a circle, not onely the centre, but any other point being taken, every moveable which departing thence, shall move in a right line, and towards any whatsoever part, shall without any doubt go towards the circumference, and continuing the motion, shall also arrive thither; so that we may truly say, that it moveth towards the circumference: but yet it doth not follow, that that which moveth by the same line with a contrary motion, would go towards the centre, unless when the point taken were the centre it self, or that the motion were made by that onely line, which produced from the point assigned, passeth thorow the centre. So that to say, that Fire moving in a right line, goeth towards the circumference of the World, therefore the parts of the Earth which by the same lines move with a contrary motion, go towards the centre of the World, concludeth not, unless then when it is presupposed, that the lines of the Fire prolonged pass by the centre of the World; and because we know certainly of them, that they pass by the centre of the Terrestrial Globe (being perpendicular to its superficies, and not inclined) therefore to conclude, it must be supposed, that the centre of the Earth is the same with the centre of the World; or at least, that the parts of the Fire and Earth descend not, save onely by one sole line which passeth by the centre of the World. Which nevertheless is false, and repugnant to experience, which sheweth us, that the parts of Fire, not by one line onely, but by infinite, produced from the centre of the Earth towards all the parts of the World, ascend always by lines perpendicular to the Superficies of the Terrestrial Globe.
Salv.You do very ingeniously lead Aristotle to the same inconvenience, Sagredus, shewing his manifest equivoke; but withal you add another inconsistency. We see the Earth to be spherical, and therefore are certain that it hath its centre, to which we see all its parts are moved; for so we must say, whilst their motions are all perpendicular to the Superficies of the Earth; we mean, that as they move to the centre of the Earth, they move to their Whole, and to their Universal Mother: and we are still farther so free, that we will suffer our selves to be perswaded, that their natural instinct is,Grave bodies may more rationally be affirmed to tend to the Centre of the Earth, than of the Universe. not to go towards the centre of the Earth, but towards that of the Universe; which we know not where to find, or whether it be or no; and were it granted to be, it is but an imaginary point, and a nothing without any quality. As to what Simplicius said last, that the contending whether the parts of the Sun, Moon, or other cœlestial Body, separated from their Whole, should naturally return to it, is a vanity, for that the case is impossible; it being clear by the Demonstrations of Aristotle, that the cœlestial Bodies are impassible,The conditions and attributes which differ the cœlestial bodies from Elementary, depend on the motions assigned them by Arist. impenetrable, unpartable, &c. I answer, that none of the conditions, whereby Aristotle distinguisheth the Cœlestial Bodies from Elementary, hath other foundation than what he deduceth from the diversity of the natural motion of those and these; insomuch that it being denied, that the circular motion is peculiar to Cœlestial Bodies, and affirmed, that it is agreeable to all Bodies naturally moveable, it is behoofull upon necessary consequence to say, either that the attributes of generable, or ingenerable, alterable, or unalterable, partable, or unpartable, &c. equally and commonly agree with all worldly bodies, namely, as well to the Cœlestial as to the Elementary; or that Aristotle hath badly and erroneously deduced those from the circular motion, which he hath assigned to Cœlestial Bodies.
Simpl.This manner of argumentation tends to the subversion of all Natural Philosophy, and to the disorder and subversion of Heaven and Earth, and the whole Universe; but I believe the Fundamentals of the Peripateticks are such, that we need not fear that new Sciences can be erected upon their ruines.
Salv.Take no thought in this place for Heaven or the Earth, neither fear their subversion, or the ruine of Philosophy. As to Heaven, your fears are vain for that which you your self hold unalterable and impassible; as for the Earth, we strive to enoble and perfect it, whilst we make it like to the Cœlestial Bodies, and as it were place it in Heaven, whence your Philosophers have exiled it.The disputes and contradictions of Philosophers may conduce to the benefit of Philosophy. Philosophy it self cannot but receive benefit from our Disputes, for if our conceptions prove true, new Discoveries will be made; if false, the first Doctrine will be more confirmed. Rather bestow your care upon some Philosophers, and help and defend them; for as to the Science it self, it cannot but improve. And that we may return to our purpose, be pleased freely to produce what presents it self to you in confirmation of that great difference which Aristotle puts between the Cœlestial Bodies, and the Elementary parts of the World, in making those ingenerable, incorruptible, unalterable, &c. and this corruptible, alterable, &c.
Simpl.I see not yet any need that Aristotle hath of help, standing as he doth stoutly and strongly on his feet; yea not being yet assaulted, much less foiled by you. And what ward will you choose in this combate for this first blow?Aristotles discourse to prove the incorruptibility of Heaven. Aristotle writeth, that whatever is generated, is made out of a contrary in some subject, and likewise is corrupted in some certain subject from a contrary into a contrary;Generation & corruption is onely amongst contraries, according to Arist. so that (observe) corruption and generation is never but onely in contraries; If therefore to a Cœlestial Body no contrary can be assigned, for that to the circular motion no other motion is contrary,To the circular motion no other motion is contrary. then Nature hath done very well to make that exempt from contraries, which was to be ingenerable and incorruptible, This fundamental first confirmed, it immediately followeth of consequence, that it is inaugmentable, inalterable, impassible, and finally eternal, and a proportionate habitation to the immortal Deities,Heaven an habitation for the immortal Gods. conformable to the opinion even of all men that have any conceit of the Gods. He afterwards confirmeth the same by sense;Immutability of Heaven evident to sense. in regard, that in all times past, according to memory or tradition, we see nothing removed, according to the whole outward Heaven, nor any of its proper parts. Next, as to the circular motion,He proveth that the circular motion hath no contrary. that no other is contrary to it, Aristotle proveth many ways; but without reciting them all, it is sufficiently demonstrated, since simple motions are but three, to the medium, from the medium, and about the medium, of which the two right, sursum and deorsum, are manifestly contrary; and because one onely hath onely one for contrary, therefore there rests no other motion which may be contrary to the circular. You see the subtle and most concluding discourse of Aristotle, whereby he proveth the incorruptibility of Heaven.
Salv.This is nothing more, save the pure progress of Aristotle, by me hinted before; wherein, besides that I affirm, that the motion which you attribute to the Cœlestial Bodies agreeth also to the Earth, its illation proves nothing. I tell you therefore, that that circular motion which you assign to Cœlestial Bodies, suiteth also to the Earth, from which, supposing that the rest of your discourse were concludent, will follow one of these three things, as I told you a little before, and shall repeat; namely, either that the Earth it self is also ingenerable, and incorruptible, as the Cœlestial bodies; or that the Cœlestial bodies are, like as the Elementary generable, alterable &c. or that this difference of motion hath nothing to do with Generation and Corruption. The discourse of Aristotle, and yours also contain many Propositions not to be lightly admitted, and the better to examine them, it will be convenient to reduce them to the most abstracted and Page 27 distinct that can be possible; and excuse me Sagredus, if haply with some tediousness you hear me oft repeat the same things, and fancie that you see me reassume my argument in the publick circle of Disputations. You say Generation and Corruption are onely made where there are contraries; contraries are onely amongst simple natural bodies, moveable with contrary motions; contrary motions are onely those which are made by a right line between contrary terms; and these are onely two, that is to say, from the medium, and towards the medium; and such motions belong to no other natural bodies, but to the Earth, the Fire, and the other two Elements: therefore Generation and Corruption is onely amongst the Elements. And because the third simple motion, namely, the circular about the medium, hath no contrary, (for that the other two are contraries, and one onely, hath but onely one contrary) therefore that natural body with which such motion agreeth, wants a contrary; and having no contrary is ingenerable and incorruptible, &c. Because where there is no contrariety, there is no generation or corruption, &c. But such motion agreeth onely with the Cœlestial bodies; therefore onely these are ingenerable,Its easier to prove the Earth to move, than that corruption is made by contraries. incorruptible, &c. And to begin, I think it a more easie thing, and sooner done to resolve, whether the Earth (a most vast Body, and for its vicinity to us, most tractable) moveth with a speedy motion, such as its revolution about its own axis in twenty four hours would be, than it is to understand and resolve, whether Generation and Corruption ariseth from contrariety, or else whether there be such things as generation, corruption and contrariety in nature. And if you, Simplicius, can tell me what method Nature observes in working, when she in a very short time begets an infinite number of flies from a little vapour of the Must of wine, and can shew me which are there the contraries you speak of, what it is that corrupteth, and how; I should think you would do more than I can; for I profess I cannot comprehend these things. Besides, I would very gladly understand how, and why these corruptive contraries are so favourable to Daws, and so cruel to Doves; so indulgent to Stags, and so hasty to Horses, that they do grant to them many more years of life, that is, of incorruptibility, than weeks to these. Peaches and Olives are planted in the same soil, exposed to the same heat and cold, to the same wind and rains, and, in a word, to the same contrarieties; and yet those decay in a short time, and these live many hundred years. Furthermore, I never was thorowly satisfied about this substantial transmutation (still keeping within pure natural bounds) whereby a matter becometh so transform'd, that it should be necessarily said to be destroy'd, so that nothing remaineth of its first being, and that another body quite differing there-from should be thence produced;Bare transposition of parts may represent bodies under diverse ⟨aspects⟩. and if I fancy to my self a body under one aspect, and by and by under another very different, I cannot think it impossible but that it may happen by a simple transposition of parts, without corrupting or ingendring any thing a-new; for we see such kinds of Metamorphoses dayly: so that to return to my purpose, I answer you, that inasmuch as you go about to perswade me that the Earth can not move circularly by way of corruptibility and generability, you have undertook a much harder task than I, that with arguments more difficult indeed, but no less concluding, will prove the contrary.
Sagr.Pardon me, Salviatus, if I interrupt your discourse, which, as it delights me much, for that I also am gravel'd with the same doubts; so I fear that you can never conclude the same, without altogether digressing from your chief design: therefore if it be permitted to proceed in our first argument, I should think that it were convenient to remit this question of generation and corruption to another distinct and single conference; as also, if it shall please you and Simplicius, we may do by other particular questions which may fall in the way of our discourse; which I will keep in my mind to propose, and exactly discuss them some other time. Now as for the present, since you say, that if Aristotle deny circular motion to the Earth in common with other bodies Cœlestial, it thence will follow, that the same which befalleth the Earth, as to its being generable, alterable, &c. will hold also of Heaven, let us enquire no further if there be such things in nature, as generation and corruption, or not; but let us return to enquire what the Globe of the Earth doth.
Simpl.I cannot suffer my ears to hear it question'd, whether generation and corruption be in rerum naturâ, it being a thing which we have continually before our eyes,By denying Principles in the Sciences, any Paradox may be maintained. and whereof Aristotle hath written two whole Books. But if you go about to deny the Principles of Sciences, and question things most manifest, who knows not, but that you may prove what you will, and maintain any Paradox? And if you do not dayly see herbs, plants, animals to generate and corrupt, what is it that you do see? Also, do you not continually behold contrarieties contend together, and the Earth change into Water, the Water turn to Air, the Air into Fire, and again the Air to condense into Clouds, Rains, Hails and Storms?
Sagr.Yes, we see these things indeed, and therefore will grant you the discourse of Aristotle, as to this part of generation and corruption made by contraries; but if I shall conclude by virtue of the same propositions which are granted to Aristotle, that the Cœlestial bodies themselves are also generable and corruptible, aswell as the Elementary, what will you say then?
Simpl.I will say you have done that which is impossible to be done.
Sagr.Go to; tell me, Simplicius, are not these affections contrary to one another?
Simpl.Which?
Sagr.Why these; Alterable, unalterable; passible,*Or, Impatible. *impassible; generable, ingenerable; corruptible, incorruptible?
Simpl.They are most contrary.
Sagr.Well then, if this be true, and it be also granted, that Cœlestial Bodies are ingenerable and incorruptible; I prove that of necessity Cœlestial Bodies must be generable and corruptible.
Simpl.This must needs be a Sophism.
Sagr.Hear my Argument,Cœlestial Bodies are generable and corruptible, because they are ingenerable and incorruptible. and then censure and resolve it. Cœlestial Bodies, for that they are ingenerable and incorruptible, have in Nature their contraries, which are those Bodies that be generable and corruptible; but where there is contrariety, there is also generation and corruption; therefore Cœlestial Bodies are generable and corruptible.
Simpl.Did I not say it could be no other than a Sophism? This is one of those forked Arguments called Soritæ:The forked Syllogism cal'd Σωρόιτης. like that of the Cretan, who said that all Cretans were lyars; but he as being a Cretan, had told a lye, in saying that the Cretans were lyars; it followed therefore, that the Cretans were no lyars, and consequently that he, as being a Cretan, had spoke truth: And yet in saying the Cretans were lyars, he had said true, and comprehending himself as a Cretan, he must consequently be a lyar. And thus in these kinds of Sophisms a man may dwell to eternity, and never come to any conclusion.
Sagr.You have hitherto censured it, it remaineth now that you answer it, shewing the fallacie.
Simpl.As to the resolving of it, and finding out its fallacie, do you not in the first place see a manifest contradiction in it? Cœlestial Bodies are ingenerable and incorruptible; Ergo, Cœlestial Bodies are generable and corruptible.Amongst Cœlestial Bodies there is no contrariety. And again, the contrariety is not betwixt the Cœlestial Bodies, but betwixt the Elements, which have the contrariety of the Motions, sursùm and deorsùm, and of levity and gravity; But the Heavens which move circularly, to which motion no other motion is contrary, want contrariety, and therefore they are incorruptible.
Sagr.Fair and softly, Simplicius; this contrariety whereby you say some simple Bodies become corruptible, resides it in the same Body which is corrupted, or else hath it relation to some other? I say, if, for example, humidity by which a piece of Earth is corrupted, resides it in the same Earth or in some other bodie, which must either be the Air or Water? I believe you will grant, that like as the Motions upwards and downwards, and gravity and levity, which you make the first contraries, cannot be in the same Subject, so neither can moist and dry, hot and cold: you must therefore consequently acknowledg that when a bodie corrupteth, Contraries which are the causes of corruption, reside not in the same body that corrupteth.it is occasioned by some quality residing in another contrary to its own: therefore to make the Cœlestial Body become corruptible, it sufficeth that there are in Nature, bodies that have a contrariety to that Cœlestial body; and such are the Elements, if it be true that corruptibility be contrary to incorruptibility.
Simpl.This sufficeth not, Sir; The Elements alter and corrupt, because they are intermixed, and are joyn'd to one another, and so may exercise their contrariety;Cœlestial Bodies touch, but are not touched by the Elements. but Cœlestial bodies are separated from the Elements, by which they are not so much as toucht, though indeed they have an influence upon the Elements. It is requisite, if you will prove generation and corruption in Cœlestial bodies, that you shew, that there resides contrarieties between them.
Sagr.See how I will find those contrarieties between them. The first fountain from whence you derive the contrariety of the Elements, is the contrariety of their motions upwards and downwards: it therefore is necessary that those Principles be in like manner contraries to each other,Gravity & levity, varity and density, are contrary qualities. upon which those motions depend: and because that is moveable upwards by lightness, and this downwards by gravity, it is necessary that lightness and gravity are contrary to each other: no less are we to believe those other Principles to be contraries, which are the causes that this is heavy, and that light: but by your own confession, levity and gravity follow as consequents of rarity and density; therefore rarity and density shall be contraries:The stars infinitely surpass the substance of the rest of Heaven in density. the which conditions or affections are so amply found in Cœlestial bodies, that you esteem the stars to be onely more dense parts of their Heaven: and if this be so, it followeth that the density of the stars exceeds that of the rest of Heaven, by almost infinite degrees: which is manifest, in that Heaven is infinitely transparent, and the stars extremely opacous; and for that there are there above no other qualities, but more and less density and rarity, which may be causes of the greater or less transparency. There being then such contrariety between the Cœlestial bodies, it is necessary that they also be generable and corruptible, in the same manner as the Elementary bodies are; or else that contrariety is not the cause of corruptibility,Rarity & density in Cœlestial bodies, is different from the rarity & density of the elements. &c.
Simpl.There is no necessity either of one or the other, for that density and rarity in Cœlestial bodies, are not contraries to each other, as in Elementary bodies; for that they depend not on the primary qualities, cold and heat, which are contraries; but on the more or less matter in proportion to quantity: now much and little, speak onely a relative opposition, that is, the least of oppositions, and which hath nothing to do with generation and corruption.
Sagr.Therefore affirming, that density and rarity, which amongst the Elements should be the cause of gravity and levity, which may be the causes of contrary motions sursum and deorsùm, on which, again, dependeth the contrarieties for generation and corruption; it sufficeth not that they be those densnesses and rarenesses which under the same quantity, or (if you will) mass contain much or little matter, but it is necessary that they be densnesses and rarenesses caused by the primary qualities, hot and cold, otherwise they would operate nothing at all: but if this be so,Aristotle defective in assigning the causes why the elements are generable & corruptible. Aristotle hath deceived us, for that he should have told it us at first, and so have left written that those simple bodies are generable and corruptible, that are moveable with simple motions upwards and downwards, dependent on levity and gravity, caused by rarity and density, made by much or little matter, by reason of heat and cold; and not to have staid at the simple motion sursum and deorsùm: for I assure you that to the making of bodies heavy or light, whereby they come to be moved with contrary motions, any kind of density and rarity sufficeth, whether it proceed from heat and cold, or what else you please; for heat and cold have nothing to do in this affair: and you shall upon experiment find, that a red iron, which you must grant to have heat, weigheth as much, and moves in the same manner as when it is cold. But to overpass this also, how know you but that Cœlestial rarity and density depend on heat and cold?
Simpl.I know it, because those qualities are not amongst Cœlestial bodies, which are neither hot nor cold.
Salv.I see we are again going about to engulph our selves in a bottomless ocean, where there is no getting to shore; for this is a Navigation without Compass, Stars, or Rudder: so that it will follow either that we be forced to pass from Shelf to Shelf, or run on ground, or to sail continually in danger of being lost. Therefore, if according to your advice we shall proceed in our main design, we must of necessity for the present overpass this general consideration, whether direct motion be necessary in Nature, and agree with some bodies; and come to the particular demonstrations, observations and experiments; propounding in the first place all those that have been hitherto alledged by Aristotle, Ptolomey, and others, to prove the stability of the Earth, endeavouring in the next place to answer them: and producing in the last place, those, by which others may be perswaded, that the Earth is no less than the Moon, or any other Planet to be numbered amongst natural bodies that move circularly.
Sagr.I shall the more willingly incline to this, in that I am better satisfied with your Architectonical and general discourse, than with that of Aristotle, for yours convinceth me without the least scruple, and the other at every step crosseth my way with some block. And I see no reason why Simplicius should not be presently satisfied with the Argument you alledg, to prove that there can be no such thing in nature as a motion by a right line, if we do but presuppose that the parts of the Universe are disposed in an excellent constitution and perfect order.
Salv.Stay a little, good Sagredus, for just now a way comes into my mind, how I may give Simplicius satisfaction, provided that he will not be so strictly wedded to every expression of Aristotle, as to hold it heresie to recede in any thing from him. Nor is there any question to be made, but that if we grant the excellent disposition and perfect order of the parts of the Universe, as to local scituation, that then there is no other but the circular motion, and rest; for as to the motion by a right line, I see not how it can be of use for any thing, but to reduce to their natural constitution, some integral bodies, that by some accident were remov'd and separated from their whole, as we said above.
Let us now consider the whole Terrestrial Globe, and enquire the best we can, whether it, and the other Mundane bodies are to conserve themselves in their perfect and natural disposition. It is necessary to say, either that it rests and keeps perpetually immoveable in its place; or else that continuing always in its place, it revolves in its self; or that it turneth about a Centre, moving by the circumference of a circle.Arist. & Ptolomey make the Terrestrial Globe immoveable. Of which accidents, both Aristotle and Ptolomey, and all their followers say, that it hath ever observed, and shall continually keep the first, that is, a perpetual rest in the same place.It is better to say, that the Terrestrial Globe naturally resteth, than that it moveth directly downwards. Now, why, I pray you, ought they not to have said, that its natural affection is to rest immoveable, rather than to make natural unto it the motion * downwards, with which motion it never did or shall move? And as to the motion by a right line, they must grant us that Nature maketh use of it to reduce the * The word is, all' ingiù, which the Latine version rendreth sursùm, which is quite contrary to the Authors sense. small parts of the Earth, Water, Air, Fire, and every other integral Mundane body to their Whole, when any of them by chance are separated, and so transported out of their proper place; if also haply, some circular motion might not be found to be more convenient to make this restitution. In my judgment, this primary position answers much better, even according to Aristotles own method, to all the other consequences, than to attribute the straight motion to be an intrinsick and natural principle of the Elements. Which is manifest, for that if I aske the Peripatetick, if, being of opinion that Cœlestial bodies are incorruptibe and eternal, he believeth that the Terrestial Globe is not so, but corruptible and mortal, so that there shall come a time, when the Sun and Moon and other Stars, continuing their beings and operations, the Earth shall not be found in the World, but shall with the rest of the Elements be destroyed and annihilated, I am certain that he would answer me, no: therefore generation and corruption is in the parts and not in the whole;Right Motion with more reason attributed to the parts, than to the whole Elements. and in the parts very small and superficial, which are, as it were, incensible in comparison of the whole masse. And because Aristotle deduceth generation and corruption from the contrariety of streight motions, let us remit such motions to the parts, which onely change and decay, and to the whole Globe and Sphere of the Elements, let us ascribe either the circular motion, or a perpetual consistance in its proper place: the only affections apt for perpetuation, and maintaining of perfect order. This which is spoken of the Earth, may be said with the same reason of Fire, and of the greatest part of the Air; to which Elements,The Peripateticks improperly assign those motious to the Elements for Natural, with which they never were moved, and those for Preternatural with which they alwayes are moved. the Peripateticks are forced to ascribe for intrinsical and natural, a motion wherewith they were never yet moved, nor never shall be; and to call that motion preternatural to them, wherewith, if they move at all, they do and ever shall move. This I say, because they assign to the Air and Fire the motion upwards, wherewith those Elements were never moved, but only some parts of them, and those were so moved onely in order to the recovery of their perfect constitution, when they were out of their natural places; and on the contrary they call the circular motion preternatural to them, though they are thereby incessantly moved: forgeting, as it seemeth, what Aristotle oft inculcateth, that nothing violent can be permanent.
Simpl.To all these we have very pertinent answers,Sensible experiments to be preferred to humane Arguments. which I for this time omit, that we may come to the more particular reasons, and sensible experiments, which ought in conclusion to be opposed, as Aristotle saith well, to whatever humane reason can present us with.
Sagr.What hath been spoken hitherto, serves to clear up unto us which of the two general discourses carrieth with it most of probability, I mean that of Aristotle, which would perswade us, that the sublunary bodies are by nature generable, and corruptible, &c. and therefore most different from the essence of Cœlestial bodies, which are impassible, ingenerable, incorruptible, &c. drawn from the diversity of simple motions; or else this of Salviatus, who supposing the integral parts of the World to be disposed in a perfect constitution, excludes by necessary consequence the right or straight motion of simple natural bodies, as being of no use in nature, and esteems the Earth it self also to be one of the Cœlestial bodies adorn'd with all the prerogatives that agree with them; which last discourse is hitherto much more likely, in my judgment, than that other. Therefore resolve, Simplicius, to produce all the particular reasons, experiments and observations, as well Natural as Astronomical, that may serve to perswade us that the Earth differeth from the Cœlestial bodies, is immoveable, and situated in the Centre of the World, and what ever else excludes its moving like to the Planets, as Jupiter or the Moon, &c. And Salviatus will be pleased to be so civil as to answer to them one by one.
Simpl.See here for a begining, two most convincing Arguments to demonstrate the Earth to be most different from the Cœlestial bodies. First, the bodies that are generable, corruptible, alterable, &c. are quite different from those that are ingenerable, incorruptible, unalterable, &c. But the Earth is generable, corruptible, alterable, &c. and the Cœlestial bodies ingenerable, incorruptible, unalterable, &c. Therefore the Earth is quite different from the Cœlestial bodies.
Sagr.By your first Argument you spread the Table with the same Viands, which but just now with much adoe were voided.
Simpl.Hold a little, Sir, and take the rest along with you, and then tell me if this be not different from what you had before. In the former, the Minor was proved à priori, & now you see it proved à posteriori: Judg then if it be the same. I prove the Minor, therefore (the Major being most manifest) by sensible experience, which shews us that in the Earth there are made continual generations, corruptions, alterations, &c. which neither our senses, nor the traditions or memories of our Ancestors, ever saw an instance of in Heaven; therefore Heaven is unalterable, &c. and the Earth alterable,Heaven immutable, because there never was any mutation seen in it. &c. and therefore different from Heaven. I take my second Argument from a principal and essential accident, and it is this. That body which is by its nature obscure and deprived of light,Bodies naturally lucid, are different from those which are by nature obscure. is divers from the luminous and shining bodies; but the Earth is obscure and void of light, and the Cœlestial bodies splendid, and full of light; Ergo, &c. Answer to these Arguments first, that we may not heap up too many, and then I will alledge others.
Salv.As to the first, the stresse whereof you lay upon experience, I desire that you would a little more distinctly produce me the alteration which you see made in the Earth, and not in Heaven; upon which you call the Earth alterable, and the Heavens not so.
Simpl.I see in the Earth, plants and animals continually generating and decaying; winds, rains, tempests, storms arising; and in a word, the aspect of the Earth to be perpetually metamorphosing; none of which mutations are to be discern'd in the Cœlestial bodies; the constitution and figuration of which is most punctually conformable to that they ever were time out of mind; without the generation of any thing that is new, or corruption of any thing that was old.
Salv.But if you content your self with these visible, or to say better, seen experiments, you must consequently account China and America Cœlestial bodies, for doubtlesse you never be held in them these alterations which you see here in Italy, and that therefore according to your apprehension they are inalterable.
Simpl.Though I never did see these alterations sensibly in those places, the relations of them are not to be questioned; besides that, cum eadem sit ratio totius, & partium, those Countreys being a part of the Earth, as well as ours, they must of necessity be alterable as these are.
Salv.And why have you not, without being put to believe other mens relations, examined and observed those alterations with your own eyes?
Simpl.Because those places, besides that they are not exposed to our eyes, are so remote, that our sight cannot reach to comprehend therein such like mutations.
Salv.See now, how you have unawares discovered the fallacy of your Argument; for, if you say that the alterations that are seen on the Earth neer at hand, cannot, by reason of the too great distance, be seen in America, much lesse can you see them in the Moon, which is so many hundred times more remote: And if you believe the alterations in Mexico upon the report of those that come from thence, what intelligence have you from the Moon, to assure you that there is no such alterations in it? Therefore, from your not seeing any alterations in Heaven, whereas, if there were any such, you could not see them by reason of their too great distance, and from your not having intelligence thereof, in regard that it cannot be had, you ought not to argue, that there are no such alterations; howbeit, from the seeing and observing of them on Earth, you well argue that therein such there are.
Simpl.I will shew so great mutations that have befaln on the Earth; that if any such had happened in the Moon, they might very well have been observed here below.The Mediterranian Sea made by the separation of Abila and Calpen. We find in very antient records, that heretofore at the Streights of Gibraltar, the two great Mountains Abila, and Calpen, were continued together by certain other lesse Mountains, which there gave check to the Ocean: but those Hills, being by some cause or other separated, and a way being opened for the Sea to break in, it made such an inundation, that it gave occasion to the calling of it since the Mid-land Sea: the greatness whereof considered, and the divers aspects the surfaces of the Water and Earth then made, had it been beheld afar off, there is no doubt but so great a change might have been discerned by one that was then in the Moon; as also to us inhabitants of the Earth, the like alterations would be perceived in the Moon; but we find not in antiquity, that ever there was such a thing seen; therefore we have no cause to say, that any of the Cœlestial bodies are alterable, &c.
Salv.That so great alterations have hapned in the Moon, I dare not say, but for all that, I am not yet certain but that such changes might occur; and because such a mutation could onely represent unto us some kind of variation between the more clear, and more obscure parts of the Moon, I know not whether we have had on Earth observant Selenographers, who have for any considerable number of years, instructed us with so exact Selenography, as that we should confidently conclude, that there hath no such change hapned in the face of the Moon; of the figuration of which I find no more particular description, than the saying of some, that it represents an humane face; of others, that it is like the muzle of a Lyon; and of others, that it is Cain with a bundle of thorns on his back: therefore, to say Heaven is unalterable, because that in the Moon, or other Cœlestial bodies, no such alterations are seen, as discover themselves on Earth, is a bad illation, and concludeth nothing.
Sagr.And there is another odd kind of scruple in this Argument of Simplicius, running in my mind, which I would gladly have answered; therefore I demand of him, whether the Earth before the Mediterranian inundation was generable and corruptible, or else began then so to be?
Simpl.It was doubtless generable and corruptible also before that time; but that was so vast a mutation, that it might have been observed as far as the Moon.
Sagr.Go to; if the Earth was generable and corruptible before that Inundation, why may not the Moon be so likewise without such a change? Or why should that be necessary in the Moon, which importeth nothing on Earth?
Salv.It is a shrewd question: But I am doubtfull that Simplicius a little altereth the Text of Aristotle, and the other Peripateticks, who say, they hold the Heavens unalterable, for that they see therein no one star generate or corrupt, which is probably a less part of Heaven, than a City is of the Earth, and yet innumerable of these have been destroyed, so as that no mark of them hath remain'd.
Sagr.I verily believed otherwise, and conceited that Simplicius dissembled this exposition of the Text, that he might not charge his Master and Consectators, with a notion more absurd than the former. And what a folly it is to say the Cœlestial part is unalterable, because no stars do generate or corrupt therein? What then? hath any one seen a Terrestrial Globe corrupt, and another regenerate in its place? And yet is it not on all hands granted by Philosophers, that there are very few stars in Heaven less than the Earth,Its no leß impossible for a star to corrupt, than for the whole Terrestrial Globe. but very many that are much bigger? So that for a star in Heaven to corrupt, would be no less than if the whole Terrestrial Globe should be destroy'd. Therefore, if for the true proof of generation and corruption in the Universe, it be necessary that so vast bodies as a star, must corrupt and regenerate, you may satisfie your self and cease your opinion; for I assure you, that you shall never see the Terrestrial Globe or any other integral body of the World, to corrupt or decay so, that having been beheld by us for so many years past, they should so dissolve, as not to leave any footsteps of them.
Salv.But to give Simplicius yet fuller satisfaction, and to reclaim him,Aristotle would change his opinion, did he see the novelties of our age. if possible, from his error; I affirm, that we have in our age new accidents and observations, and such, that I question not in the least, but if Aristotle were now alive, they would make him change his opinion; which may be easily collected from the very manner of his discoursing: For when he writeth that he esteemeth the Heavens inalterable, &c. because no new thing was seen to be begot therein, or any old to be dissolved, he seems implicitely to hint unto us, that when he should see any such accident, he would hold the contrary: and confront, as indeed it is meet, sensible experiments to natural reason: for had he not made any reckoning of the senses, he would not then from the not seeing of any sensible mutation, have argued immutability.
Simpl.Aristotle deduceth his principal Argument à priori, shewing the necessity of the inalterability of Heaven by natural, manifest and clear principles; and then stablisheth the same à posteriori, by sense, and the traditions of the antients.
Salv.This you speak of is the Method he hath observed in delivering his Doctrine, but I do not bethink it yet to be that wherewith he invented it; for I do believe for certain, that he first procured by help of the senses, such experiments and observations as he could,The certainty of the conclusion helpeth by a resolutive method to find the demonstration. to assure him as much as it was possible, of the conclusion, and that he afterwards sought out the means how to demonstrate it: For this is the usual course in demonstrative Sciences, and the reason thereof is, because when the conclusion is true, by help of resolutive Method, one may hit upon some proposition before demonstrated, or come to some principle known per se; but if the conclusion be false, a man may proceed in infinitum, and never meet with any truth already known; but very oft he shall meet with some impossibility or manifest absurdity. Pythagoras offered an Hecatomb for a Geometrical demonstration which he found. Nor need you question but that Pythagoras along time before he found the demonstration for which he offered the Hecatomb, had been certain, that the square of the side subtending the right angle in a rectangle triangle, was equal to the square of the other two sides: and the certainty of the conclusion conduced not a little to the investigating of the demonstration, understanding me alwayes to mean in demonstrative Sciences. But what ever was the method of Aristotle, and whether his arguing à priori preceded sense à posteriori, or the contrary; it sufficeth that the same Aristotle preferreth (as hath been oft said) sensible experiments before all discourses; besides, as to the Arguments à priori their force hath been already examined. Now returning to my purposed matter, I say, that the things in our times discovered in the Heavens, are, and have been such, that they may give absolute satisfaction to all Philosophers; forasmuch as in the particular bodies, and in the universal expansion of Heaven, there have been, and are continually, seen just such accidents as we call generations and corruptions, being that excellent Astronomers have observed many Comets generated and dissolved in parts higher than the Lunar Orb, besides the two new Stars, Anno 1572,New stars discovered in Heaven. and Anno 1604, without contradiction much higher than all the Planets; and in the face of the Sun it self, by help of the Telescope,Spots generate and dissolve in the face of the Sun. certain dense and obscure substances, in semblance very like to the foggs about the Earth, are seen to be produced and dissolved; and many of these are so vast, that they far exceed not only the Mediterranian Streight, but all Affrica and Asia also.Solar spots are bigger than all Asia and Affrick. Now if Aristotle had seen these things, what think you he would have said, and done Simplicius?
Simpl.I know not what Aristotle would have done or said, that was the great Master of all the Sciences, but yet I know in part, what his Sectators do and say, and ought to do and say, unlesse they would deprive themselves of their guide, leader, and Prince in Philosophy. As to the Comets, are not those Modern Astronomers, who would make them Cœlestial, convinced by the * Astronomers confuted by Anti-Tycho* Anti-Tycho, yea, and overcome with their own weapons, I mean by way of Paralaxes and Calculations, every way tryed, concluding at the last in favour of Aristotle, that they are all Elementary? And this being overthrown, which was as it were their foundation, have these Novellists any thing more wherewith to maintain their assertion?
Salv.Hold a little, good Simplicius, this modern Author, what saith he to the new Stars, Anno 1572, and 1604, and to the Solar spots? for as to the Comets, I for my own particular little care to make them generated under or above the Moon; nor did I ever put much stresse on the loquacity of Tycho; nor am I hard to believe that their matter is Elementary, and that they may elevate (sublimate) themselves at their pleasure, without meeting with any obstacle from the impenetrability of the Peripatetick Heaven, which I hold to be far more thin, yielding, and subtil than our Air; and as to the calculations of the Parallaxes, first, the uncertainty whether Comets are subject to such accidents, and next, the inconstancy of the observations, upon which the computations are made, make me equally suspect both those opinions:Anti-Tycho wresteth Astronomical observations to his own purpose. and the rather, for that I see him you call Anti-Tycho, sometimes stretch to his purpose, or else reject those observations which interfere with his design.
Simpl.As to the new Stars, Anti-Tycho extricates himself finely in three or four words; saying, That those modern new Stars are no certain parts of the Cœlestial bodies, and that the adversaries, if they will prove alteration and generation in those superior bodies, must shew some mutations that have been made in the Stars described so many ages past, of which there is no doubt but that they be Cœlestial bodies, which they can never be able to do: Next, as to those matters which some affirm, to generate and dissipate in the face of the Sun, he makes no mention thereof; wherefore I conclude, that he believed them fictious, or the illusions of the Tube, or at most, some petty effects caused by the Air, and in brief, any thing rather than matters Cœlestial.
Salv.But you, Simplicius, what answer could you give to the opposition of these importunate spots which are started up to disturb the Heavens, and more than that, the Peripatetick Philosophy? It cannot be but that you, who are so resolute a Champion of it, have found some reply or solution for the same, of which you ought not to deprive us.
Simpl.I have heard sundry opinions about this particular. One saith: "They are Stars which in their proper Orbs,Sundry opinions touching the Solar spots. like as Venus and Mercury, revolve about the Sun, and in passing under it, represent themselves to us obscure; and for that they are many, they oft happen to aggregate their parts together, and afterwards seperate again. Others believe them to be äerial impressions; others, the illusions of the chrystals; and others, other things: But I incline to think, yea am verily perswaded, That they are an aggregate of many several opacous bodies, as it were casually concurrent among themselves. And therefore we often see, that in one of those spots one may number ten or more such small bodies, which are of irregular figures, and seem to us like flakes of snow, or flocks of wooll, or moaths flying: they vary fire amongst themselves, and one while sever, another while meet, and most of all beneath the Sun, about which, as about their Centre, they continually move. But yet, must we not therefore grant, that they are generated or dissolved, but that at sometimes they are hid behind the body of the Sun, and at other times, though remote from it, yet are they not seen for the vicinity of the immeasurable light of the Sun; in regard that in the eccentrick Orb of the Sun, there is constituted, as it were, an Onion, composed of many folds one within another, each of which, being * The Original saith [tempestata si muove] which the Latine Translation, (Mistaking Tempestata, a word in Heraldry, for Tempestato,) rendereth [incitata movetur] which signifieth a violent transportmeut, as in a storm, that of a Ship. * studded with certain small spots, doth move; and albeit their motion at first seemeth inconstant and irregular, yet neverthelesse, it is said at last, to be observed that the very same spots, as before, do within a determinate time return again." This seemeth to me the fittest answer that hath been found to assigne a reason of that same appearance, and withal to maintain the incorruptability and ingenerability of the Heavens; and if this doth not suffice; there wants not more elevated wits, which will give you other more convincing.
Salv.If this of which we dispute, were some point of Law, or other part of the Studies called Humanity,In natural Sciences, the art of Oratory is of no force. wherein there is neither truth nor falshood, if we will give sufficient credit to the acutenesse of the wit, readinesse of answers, and the general practice of Writers, then he who most aboundeth in these, makes his reason more probable and plausible; but in Natural Sciences, the conclusions of which are true and necessary, and wherewith the judgment of men hath nothing to do, one is to be more cautious how he goeth about to maintain any thing that is false; for a man but of an ordinary wit, if it be his good fortune to be of the right side, may lay a thousand Demosthenes and a thousand Aristotles at his feet. Therefore reject those hopes and conceits, wherewith you flatter your self, that there can be any men so much more learned, read, and versed in Authors, than we, that in despite of nature, they should be able to make that become true, which is false. And seeing that of all the opinions that have been hitherto alledged touching the essence of these Solar spots, this instanced in by you, is in your judgment the truest, it followeth (if this be so) that all the rest are false; and to deliver you from this also, which doubtlesse is a most false Chimæra, over-passing infinite other improbabilities that are therein,An Argument that necessarily proveth the Solar spots to generate and dissolve. I shall propose against it onely two experiments; one is, that many of those spots are seen to arise in the midst of the Solar ring, and many likewise to dissolve and vanish at a great distance from the circumference of the Sun; a necessary Argument that they generate and dissolve; for if without generating or corrrupting, they should appear there by onely local motion, they would all be seen to enter,A conclusive demonstration, that the spots are contiguous to the body of the Sun. and pass out by extreme circumference. The other observation to such as are not situate in the lowest degree of ignorance in Perspective, by the mutation of the appearing figures, and by the apparent mutations of the velocity of motion is necessarily concluding, that the spots are contiguous to the body of the Sun, and that touching its superficies, they move either with it or upon it, and that they in no wise move in circles remote from the same.The motion of the spots towards the circumference of the Sun appears slow. The motion proves it, which towards the circumference of the Solar Circle, appeareth very slow, and towards the midst, more swift; the figures of the spots confirmeth it,The figure of the spots appears narrow towards the circumference of the Suns discus, & why. which towards the circumference appear exceeding narrow in comparison of that which they seem to be in the parts nearer the middle; and this because in the midst they are seen in their full luster, and as they truly be; and towards the circumference by reason of the convexity of the globous superficies, they seem more compress'd: And both these diminutions of figure and motion, to such as know how to observe and calculate them exactly, precisely answer to that which should appear, the spots being contiguous to the Sun, and differ irreconcileably from a motion in circles remote, though but for smal intervalls from the body of the Sun; as hath been diffusely demonstrated by our* Under this word Friend, as also that of Academick, & Common Friend, Galilœus modestly conceals himself throughout these Dialogues. * Friend, in his Letters about the Solar spots, to Marcus Velserus. It may be gathered from the same mutation of figure, that none of them are stars, or other bodies of spherical figure; for that amongst all figures the sphere never appeareth compressed, nor can ever be represented but onely perfectly round; and thus in case any particular spot were a round body, as all the stars are held to be, the said roundness would as well appear in the midst of the Solar ring, as when the spot is near the extreme: whereas, its so great compression, and shewing its self so small towards the extreme, and contrariwise, spatious and large towards the middle, assureth us,The Solar spots are not spherical, but flat like thin plates. that these spots are flat plates of small thickness or depth, in comparison of their length and breadth. Lastly, whereas you say that the spots after their determinate periods are observed to return to their former aspect, believe it not, Simplicius, for he that told you so, will deceive you; and that I speak the truth, you may observe them to be hid in the face of the Sun far from the circumference; nor hath your Observator told you a word of that compression, which necessarily argueth them to be contiguous to the Sun. That which he tells you of the return of the said spots, is nothing else but what is read in the forementioned Letters, namely, that some of them may sometimes so happen that are of so long a duration, that they cannot be dissipated by one sole conversion about the Sun, which is accomplished in less than a moneth.
Simpl.I, for my part, have not made either so long, or so exact observations, as to enable me to boast my self Master of the Quod est of this matter: but I will more accurately consider the same, and make tryal my self for my own satisfaction, whether I can reconcile that which experience shews us, with that which Aristotle teacheth us; for it's a certain Maxim, that two Truths cannot be contrary to one another.
Salv. If you would reconcile that which sense shewed you, with the solider Doctrines of Aristotle,One cannot (saith Aristotle) speak confidently of Heaven, by reason of its great distance. you will find no great difficulty in the undertaking; and that so it is, doth not Aristotle say, that one cannot treat confidently of the things of Heaven, by reason of their great remoteness?
Simpl.He expresly saith so.
Salv.And doth he not likewise affirm,Aristotle prefers sense before ratiocination. that we ought to prefer that which sense demonstrates, before all Arguments, though in appearance never so well grounded? and saith he not this without the least doubt or haesitation?
Simpl.He doth so.
Salv.Why then, the second of these propositions, which are both the doctrine of Aristotle,Its a doctrine more agreeing with Aristotle, to say the Heavens are alterable, than that which affirms them inalterable. that saith, that sense is to take place of Logick, is a doctrine much more solid and undoubted, than that other which holdeth the Heavens to be unalterable; and therefore you shall argue more Aristotelically, saying, the Heavens are alterable, for that so my sense telleth me, than if you should say, the Heavens are ualterable, for that Logick so perswaded Aristotle.We may by help of the Telescope discourse better of cœlestial matters, than Aristot. himself. Furthermore, we may discourse of Cœlestial matters much better than Aristotle; because, he confessing the knowledg thereof to be difficult to him, by reason of their remoteness from the senses, he thereby acknowledgeth, that one to whom the senses can better represent the same, may philosophate upon them with more certainty. Now we by help of the Telescope, are brought thirty or forty times nearer to the Heavens, than ever Aristotle came; so that we may discover in them an hundred things, which he could not see, and amongst the rest, these spots in the Sun, which were to him absolutely invisible; therefore we may discourse of the Heavens and Sun, with more certainty than Aristolte.
Sagr.I see into the heart of Simplicius, and know that he is much moved at the strength of these so convincing Arguments; but on the other side, when he considereth the great authority which Aristotle hath won with all men, and remembreth the great number of famous Interpreters, which have made it their business to explain his sense; and seeth other Sciences, so necessary and profitable to the publick, to build a great part of their esteem and reputation on the credit of Aristotle he is much puzzled and perplexed:The Declamation of Simplicius. and methinks I hear him say, To whom then should we repair for the decision of our controversies, if Aristotle were removed from the chair? What other Author should we follow in the Schools, Academies and Studies? What Philosopher hath writ all the parts of Natural Philosophy, and that so methodically without omitting so much as one single conclusion? Shall we then overthrow that Fabrick under which so many passengers find shelter? Shall we destroy that Asylum, that Prytaneum, wherein so many Students meet with commodious harbour, where without exposing themselves to the injuries of the air, with the onely turning over of a few leaves, one may learn all the secrets of Nature? Shall we dismantle that fort in which we are safe from all hostile assaults? But I pitie him no more than I do that Gentleman who with great expence of time and treasure, and the help of many hundred artists, erects a very sumptuous Pallace, and afterwards beholds it ready to fall, by reason of the bad foundation; but being extremely unwilling to see the Walls stript which are adorned with so many beautifull Pictures; or to suffer the columns to fall, that uphold the stately Galleries; or the gilded roofs, chimney-pieces, the freizes, the cornishes of marble, with so much cost erected, to be ruined; goeth about with girders, props, shoars, butterasses, to prevent their subversion.
Salv.But alass, Simplicius as yet fears no such fall, and I would undertake to secure him from that mischief at a far less charge.Peripatetick Philosophy unchangeable. There is no danger that so great a multitude of subtle and wise Philosophers, should suffer themselves to be Hector'd by one or two, who make a little blustering; nay, they will rather, without ever turning the points of their pens against them, by their silence onely render them the object of universal scorn and contempt. It is a fond conceit for any one to think to introduce new Philosophy, by reproving this or that Author: it will be first necessary to new-mold the brains of men, and make them apt to distinguish truth from falshood. A thing which onely God can do. But from one discourse to another whither are we stray'd? your memory must help to guide me into the way again.
Simpl.I remember very well where we left. We were upon the answer of Anti-Tycho, to the objections against the immutability of the Heavens, among which you inserted this of the Solar spots, not spoke of by him; and I believe you intended to examine his answer to the instance of the New Stars. Salv.Now I remember the rest, and to proceed, Methinks there are some things in the answer to Anti-Tycho, worthy of reprehension. And first, if the two New Stars, which he can do no less than place in the uppermost parts of the Heavens, and which were of a long duration, but finally vanished, give him no obstruction in maintaining the inalterability of Heaven, in that they were not certain parts thereof, nor mutations made in the antient Stars, why doth he set himself so vigorously and earnestly against the Comets, to banish them by all ways from the Cœlestial Regions? Was it not enough that he could say of them the same which he spoke of the New stars? to wit, that in regard they were no certain parts of Heaven, nor mutations made in any of the Stars, they could no wise prejudice either Heaven, or the Doctrine of Aristotle? Secondly, I am not very well satisfied of his meaning; when he saith that the alterations that should be granted to be made in the Stars, would be destructive to the prerogative of Heaven; namely, its incorruptibility, &c. and this, because the Stars are Cœlestial substances, as is manifest by the consent of every one; and yet is nothing troubled that the same alterations should be made * Extra Stellas.* without the Stars in the rest of the Cœlestial expansion. Doth he think that Heaven is no Cœlestial substance? I, for my part, did believe that the Stars were called Cœlestial bodies, by reason that they were in Heaven, or for that they were made of the substance of Heaven; and yet I thought that Heaven was more Cœlestial than they; in like sort, as nothing can be said to be more Terrestrial, or more fiery than the Earth or Fire themselves. And again, in that he never made any mention of the Solar spots, which have been evidently demonstrated to be produced, and dissolved, and to be neer the Sun, and to turn either with, or about the same, I have reason to think that this Author probably did write more for others pleasure, than for his own satisfaction; and this I affirm, forasmuch as he having shewn himself to be skilful in the Mathematicks, it is impossible but that he should have been convinced by Demonstrations, that those substances are of necessity contiguous with the body of the Sun, and are so great generations and corruptions, that none comparable to them, ever happen in the Earth: And if such, so many, and so frequent be made in the very Globe of the Sun, which may with reason be held one of the noblest parts of Heaven, what should make us think that others may not happen in the other Orbs.
Sagr.I cannot without great admiration,Generability and alteration is a greater perfection in the Worlds bodies than the contrary qualities. nay more, denial of my understanding, hear it to be attributed to natural bodies, for a great honour and perfection that they are * Impatible.* impassible, immutable, inalterable, &c. And on the contrary, to hear it to be esteemed a great imperfection to be alterable, generable, mutable, &c.The Earth very noble, by reason of the many mutations made therein. It is my opinion that the Earth is very noble and admirable, by reason of so many and so different alterations, mutations, generations, &c. which are incessantly made therein; and if without being subject to any alteration, it had been all one vast heap of sand, or a masse of Jasper, or that in the time of the Deluge, the waters freezing which covered it, it had continued an immense Globe of Christal,The Earth unprofitable and full of idlenesse, its alterations taken away wherein nothing had ever grown, altered, or changed, I should have esteemed it a lump of no benefit to the World, full of idlenesse, and in a word superfluous, and as if it had never been in nature; and should make the same difference in it, as between a living and dead creature: The like I say of the Moon, Jupiter, and all the other Globes of the World. But the more I dive into the consideration of the vanity of popular discourses, the more empty and simple I find them. And what greater folly can there be imagined, than to call Jems, Silver and Gold pretious; and Earth and dirt vile?The Earth more noble than Gold and Jewels. For do not these persons consider, that if there should be as great a scarcity of Earth, as there is of Jewels and pretious metals, there would be no Prince, but would gladly give a heap of Diamonds and Rubies, and many Wedges of Gold, to purchase onely so much Earth as should suffice to plant a Gessemine in a little pot, or to set therein a China Orange, that he might see it sprout, grow up, and bring forth so goodly leaves, so odiriferous flowers,Scarcity and plenty enhanse and debase the price of things. and so delicate fruit? It is therefore scarcity and plenty that make things esteemed and contemned by the vulgar; who will say that same is a most beautiful Diamond, for that it resembleth a cleer water, and yet will not part with it for ten Tun of water:Incorruptibility esteemed by the vulgar out of their fear of death. These men that so extol incorruptibility, inalterability, &c. speak thus I believe out of the great desire they have to live long, and for fear of death; not considering, that if men had been immortal, they should have had nothing to do in the World.The disparagers of corruptibility deserve to be turned into Statua's. These deserve to meet with a Medusa's head, that would transform them into Statues of Dimond and Jasper, that so they might become more perfect than they are.
Salv.And it may be such a Metamorphosis would not be altogether unprofitable to them; for I am of opinion that it is better not to discourse at all, than to argue erroniously.
Simpl.There is not the least question to be made, but that the Earth is much more perfect, being as it is alterable, mutable, &c. than if it had been a masse of stone; yea although it were one entire Diamond,The Cœlestial bodies designed to serve the Earth, need no more but motion and light. most hard and impassile. But look how much these qualifications enoble the Earth, they render the Heavenly bodies again on the other side so much the more imperfect, in which, such conditions would be superfluous; in regard that the Cœlestial bodies, namely, the Sun, Moon, and the other Stars, which are ordained for no other use but to serve the Earth, need no other qualities for attaining of that end, save onely those of light and motion.
Sagr.How? Will you affirm that nature hath produced and designed so many vast perfect and noble Cœlestial bodies, impassible, immortal, and divine, to no other use but to serve the passible, frail, and mortal Earth? to serve that which you call the drosse of the World, and sink of all uncleannesse? To what purpose were the Cœlestial bodies made immortal, &c. to serve a frail, &c. Take away this subserviency to the Earth, and the innumerable multitude of Cœlestial bodies become wholly unuseful, Celestial bodies want an interchangeable operation upon each other.and superfluous, since they neither have nor can have any mutual operation betwixt themselves; because they are all unalterable, immutable, impassible: For if, for Example, the Moon be impassible, what influence can the Sun or any other Star have upon her? it would doubtlesse have far lesse effect upon her, than that of one who would with his looks or imagination, lignifie a piece of Gold. Moreover, it seemeth to me, that whilst the Cœlestial bodies concurre to the generation and alteration of the Earth, they themselves are also of necessity alterable; for otherwise I cannot understand how the application of the Sun or Moon to the Earth, to effect production, should be any other than to lay a marble Statue by a Womans side, and from that conjunction to expect children.
Simpl.Corruptibility,Alterability, &c. are not in the whole Terrestrial Globe, but in some of its parts. alteration, mutation, &c. are not in the whole Terrestrial Globe, which as to its whole, is no lesse eternal than the Sun or Moon, but it is generable and corruptible as to its external parts; but yet it is also true that likewise in them generation and corruption are perpetual, and as such require the heavenly eternal operations; and therefore it is necessary that the Cœlestial bodies be eternal.
Sagr.All this is right; but if the corruptibility of the superficial parts of the Earth be nowise prejudicial to the eternity of its whole Globe, yea, if their being generable, corruptible, alterable, &c. gain them great ornament and perfection; why cannot,Cœlestial bodies alterable in their outward parts. and ought not you to admit alteration, generation, &c. likewise in the external parts of the Cœlestial Globes, adding to them ornament, without taking from them perfection, or bereaving them of action; yea rather encreasing their effects, by granting not onely that they all operate on the Earth, but that they mutually operate upon each other, and the Earth also upon them all?
Simpl.This cannot be, because the generations, mutations, &c. which we should suppose v. g. in the Moon; would be vain and uselesse, & natura nihil frustra facit.
Sagr.And why should they be vain and uselesse?
Simpl.Because we cleerly see,The generations & mutations happening in the Earth, are all for the good of Man. and feel with our hands, that all generations, corruptions, &c. made in the Earth, are all either mediately or immediately directed to the use, convenience, and benefit of man; for the use of man are horses brought forth, for the feeding of horses, the Earth produceth grasse, and the Clouds water it; for the use and nourishment of man, herbs, corn, fruits, beasts, birds, fishes, are brought forth; and in sum, if we should one by one dilligently examine and resolve all these things, we should find the end to which they are all directed, to be the necessity, use, convenience, and delight of man. Now of what use could the generations which we suppose to be made in the Moon or other Planets, ever be to mankind? unlesse you should say that there were also men in the Moon, that might enjoy the benefit thereof; a conceit either fabulous or impious.
Sagr.That in the Moon or other Planets,The Moon hath no generatings of things, like as we have, nor is it inhabited by men. there are generated either herbs, or plants, or animals, like to ours, or that there are rains, winds, or thunders there, as about the Earth, I neither know, nor believe, and much lesse, that it is inhabited by men: but yet I understand not, because there are not generated things like to ours, that therefore it necessarily followeth, that no alteration is wrought therein, or that there may not be other things that change,In the Moon may be a generation of things different from ours. generate, and dissolve, which are not onely different from ours, but exceedingly beyond our imagination, and in a word, not to be thought of by us. And if, as I am certain, that one born and brought up in a spatious Forrest, amongst beasts and birds, and that hath no knowledg at all of the Element of Water,He that had not heard of the Element of Water, could never fancy to himself Ships and Fishes. could never come to imagine another World to be in Nature, different from the Eatth, full of living creatures, which without legs or wings swiftly move, and not upon the surface onely, as beasts do upon the Earth, but in the very bowels thereof; and not onely move, but also stay themselves and cease to move at their pleasure, which birds cannot do in the air; and that moreover men live therein, and build Palaces and Cities, and have so great convenience in travailing, that without the least trouble, they can go with their Family, House, and whole Cities, to places far remote, like as I say, I am certain, such a person, though of never so piercing an imagination, could never fancy to himself Fishes, the Ocean, Ships, Fleets, Armado's at Sea; thus, and much more easily, may it happn, that in the Moon, remote from us by so great a space, and of a substance perchance very different from the Earth, there may be matters, and operations, not only wide off, but altogether beyond all our imaginations, as being such as have no resemblance to ours, and therefore wholly inexcogitable, in regard, that what we Page 48 imagine to our selves, must necessarily be either a thing already seen, or a composition of things, or parts of things seen at another time; for such are the Sphinxes, Sirenes, Chimaera's, Centaurs, &c.
Salv.I have very often let my fancy ruminate upon these speculations, and in the end, have thought that I had found some things that neither are nor can be in the Moon; but yet I have not found therein any of those which I believe are, and may be there, save onely in a very general acceptation, namely, things that adorn it by operating, moving and living; and perhaps in a way very different from ours;There may be substances in the Moon very different from ours. beholding and admiring the greatness and beauty of the World, and of its Maker and Ruler, and with continual Encomiums singing his prayses; and in summe (which is that which I intend) doing what sacred Writers so frequently affirm, to wit, all the creatures making it their perpetual imployment to laud God.
Sagr.These are the things, which speaking in general terms, may be there; but I would gladly hear you instance in such as you believe neither are nor can be there; which perchance may be more particularly named.
Salv.Take notice Sagredus that this will be the third time that we have unawares by running from one thing to another, lost our principal subject; and if we continue these digressions, it will be long ere we come to a conclusion of our discourse; therefore I should judg it better to remit this, as also such other points, to be decided on a particular occasion.
Sagr.Since we are now got into the Moon, if you please, let us dispatch such things as concern her, that so we be not forced to such another tedious journey.
Salv.It shall be as you would have it. And to begin with things more general, I believe that the Lunar Globe is far different from the Terrestrial, though in some things they agree. I will recount first their resemblances, and next their differences. The Moon is manifestly like to the Earth in figure,The First resemblance between the Moon and Earth; which is that of figure; is proved by the manner of being illuminated by the Sun. which undoubtedly is spherical, as may be necessarily concluded from the aspect of its surface, which is perfectly Orbicular, and the manner of its receiving the light of the Sun, from which, if its surface were flat, it would come to be all in one and the same time illuminated, and likewise again in another instant of time obscured, and not those parts first, which are situate towards the Sun, and the rest successively, so that in its opposition, and not till then, its whole apparent circumference is enlightned; which would happen quite contrary, if the visible surface were concave; namely, the illumination would begin from the parts opposite or averse to the Sun.The Second conformity is the Moons being opacous as the Earth. Secondly she is as the Earth, in her self obscure and opacous, by which opacity it is enabled to receive, and reflect the light of the Sun;Thirdly, The matter of the Moon is dense and montanous as the Earth. which were it not so, it could not do. Thirdly, I hold its matter to be most dense and solid as the Earth is, which I clearly argue from the unevenness of its superficies in most places, by means of the many eminencies and cavities discovered therein by help of the Telescope: of which eminencies there are many all over it, directly resembling our most sharp and craggy mountains, of which you shall there perceive some extend and run in ledges of an hundred miles long; others are contracted into rounder forms; and there are also many craggy, solitary, steep and cliffy rocks. But that of which there are frequentest appearances, are certain Banks (I use this word, because I cannot thing of another that better expresseth them) pretty high raised, which environ and inclose fields of several bignesses, and from sundry figures, but for the most part circular; many of which have in the midst a mount raised pretty high, and some few are replenished with a matter somewhat obscure, to wit, like to the great spots discerned by the bare eye, and these are of the greatest magnitude; the number moreover of those that are lesser and lesser is very great, and yet almost all circular. Fourthly,Fourthly, The Moon is distinguished into two different parts for clarity and obscurity, as the Terrestrial Globe into Sea and Land. like as the surface of our Globe is distinguished into two principal parts, namely, into the Terrestrial and Aquatick: so in the Lunar surface we discern a great distinction of some great fields more resplendant, and some less: whose aspect makes me believe, that that of the Earth would seem very like it, The surface of the Sea would shew at a distance more obscure than that of the Earth.beheld by any one from the Moon, or any other the like distance, to be illuminated by the Sun: and the surface of the sea would appear more obscure, and that of the Earth more bright. Fifthly, like as we from the Earth behold the Moon, one while all illuminated, another while half;Fiftly, Mutation of figures in the Earth, like to those of the Moon, and made with the same periods. sometimes more, sometimes less; sometimes horned, sometimes wholly invisibly; namely, when its just under the Sun beams; so that the parts which look towards the Earth are dark: Thus in every respect, one standing in the Moon would see the illumination of the Earths surface by the Sun, with the same periods to an hair, and under the same changes of figures. Sixtly,———
Sagr.Stay a little, Salviatus; That the illumination of the Earth, as to the several figures, would represent it self to a person placed in the Moon, like in all things to that which we discover in the Moon, I understand very well, but yet I cannot conceive how it shall appear to be done in the same period; seeing that that which the Suns illumination doth in the Lunar superficies in a month, it doth in the Terrestrial in twenty four hours.
Salv.Its true, the effect of the Sun about the illuminating these two bodies, and replenishing with its splendor their whole surfaces, is dispatch'd in the Earth in a Natural day, and in the Moon in a Month; but the variation of the figures in which the illuminated parts of the Terrestrial superficies appear beheld from the Moon, depends not on this alone, but on the divers aspects which the Moon is still changing with the Sun; so that, if for instance, the Moon punctually followed the motion of the Sun, and stood, for example, always in a direct line between it and the Earth, in that aspect which we call Conjunction, it looking always to the same Hemisphere of the Earth which the Sun looks unto, she would behold the same all light: as on the contrary, if it should always stay in Opposition to the Sun, it would never behold the Earth, of which the dark part would be continually turn'd towards the Moon, and therefore invisible. But when the Moon is in Quadrature of the Sun, that half of the Terrestrial Hemisphere exposed to the sight of the Moon which is towards the Sun, is luminous; and the other towards the contrary is obscure: and therefore the illuminated part of the Earth would represent it self to the Moon in a semi-circular figure.
Sagr.I clearly perceive all this, and understand very well, that the Moon departing from its Opposition to the Sun, where it saw no part of the illumination of the Terrestrial superficies, and approaching day by day nearer the Sun, she begins by little and little to discover some part of the face of the illuminated Earth; and that which appeareth of it shall resemble a thin sickle, in regard the figure of the Earth is round: and the Moon thus acquiring by its motion day by day greater proximity to the Sun, successively discovers more and more of the Terrestrial Hemisphere enlightned, so that at the Quadrature there is just half of it visible, insomuch that we may see the other part of her: continuing next to proceed towards the Conjunction, it successively discovers more and more of its surface to be illuminated, and in fine, at the time of Conjunction seeth the whole Hemisphere enlightned. And in short, I very well conceive, that what befalls the Inhabitants of the Earth, in beholding the changes of the Moon, would happen to him that from the Moon should observe the Earth; but in a contrary order, namely, that when the Moon is to us at her full, and in Opposition to the Sun, then the Earth would be in Conjunction with the Sun, and wholly obscure and invisible; on the contrary, that position which is to us a Conjunction of the Moon with the Sun, and for that cause a Moon silent and unseen, would be there an Opposition of the Earth to the Sun, and, to so speak, Full Earth, to wit, all enlightned. And lastly, look what part of the Lunar surface appears to us from time to time illuminated, so much of the Earth in the same time shall you behold from the Moon to be obscured: and look how much of the Moon is to us deprived of light, so much of the Earth is to the Moon illuminated. In one thing yet these mutual operations in my judgment seem to differ, and it is, that it being supposed, and not granted, that some one being placed in the Moon to observe the Earth, he would every day see the whole Terrestrial superficies, by means of the Moons going about the Earth in twenty four or twenty five hours; but we never see but half of the Moon, since it revolves not in it self, as it must do to be seen in every part of it.
Salv.So that this, befals not contrarily, namely, that her revolving in her self, is the cause that we see not the other half of her, for so it would be necessary it should be, if she had the Epicycle. But what other difference have you behind, to exchange for this which you have named?
Sagr.Let me see; Well for the present I cannot think of any other.
Salv.And what if the Earth (as you have well noted) seeth no more than halfAll the Earth seeth half onely of the Moon, & the half onely of the Moon seeth all the Earth. the Moon, whereas from the Moon one may see all the Earth; and on the contrary, all the Earth seeth the Moon, and but onely half of it seeth the Earth? For the inhabitants, to so speak, of the superior Hemisphere of the Moon, which is to us invisible, are deprived of the sight of the Earth: and these haply are the Anticthones. But here I remember a particular accident, newly observed by our Academian,From the Earth we see more than half the Lunar Globe. in the Moon, from whch are gathered two necessary consequences; one is, that we see somewhat more than half of the Moon; and the other is, that the motion of the Moon hath exact concentricity with the Earth: and thus he finds the Phœnomenonand observation. When the Moon hath a correspondence and natural sympathy with the Earth, towards which it hath its aspect in such a determinate part, it is necessary that the right line which conjoyns their centers, do passe ever by the same point of the Moons superficies; so that, who so shall from the center of the Earth behold the same, shall alwayes see the same Discus or Face of the Moon punctually determined by one and the same circumference; But if a man be placed upon the Terrestrial surface, the ray which from his eye passeth to the centre of the Lunar Globe, will not pass by the same point of its superficies, by which the line passeth that is drawn from the centre of the Earth to that of the Moon, save onely when it is vertical to him: but the Moon being placed in the East, or in the West, the point of incidence of the visual ray, is higher than that of the line which conjoyns the centres; and therefore the observer may discern some part of the Lunar Hemisphere towards the upper circumference, and alike part of the other is invisible: they are discernable and undiscernable, in respect of the Hemisphere beheld from the true centre of the Earth: and because the part of the Moons circumference, which is superiour in its rising, is nethermost in its setting; therefore the difference of the said superiour and inferiour our parts must needs be very observable; certain spots and other notable things in those parts, being one while discernable, and another while not. A like variation may also be observed towards the North and South extremities of the same Discus (or Surface) according as the Moons position is in its greatest North or South Latitude; For, if it be North, some of its parts towards the North are hid, and some of those parts towards the South are discovered, and so on the contrary. Now that these consequences are really true,Two spots in the Moon, by which it is perceived that she hath respect to the centre of the Earth in her motion. is verified by the Telescope, for there be in the Moon two remarkable spots, one of which, when the Moon is in the meridian, is situate to the Northwest, and the other is almost diametrically opposite unto it; and the first of these is visible even without the Telescope; but the other is not. That towards the Northwest is a reasonable great spot of oval figure, separated from the other great ones; the opposite one is lesse, and also severed from the biggest, and situate in a very cleer field; in both these we may manifestly discern the foresaid variations, and see them one after another; now neer the edge or limb of the Lunar Discus, and anon remote, with so great difference that the distance betwixt the Northwest and the circumference of the Discus is more than twice as great at one time, as at the other; and as to the second spot (because it is neerer to the circumference) such mutation importeth more, than twice so much in the former. Hence its manifest, that the Moon, as if it were drawn by a magnetick vertue, constantly beholds the Terrestrial Globe with one and the same aspect, never deviating from the same.
Sagr.Oh! when will there be an end put to the new observations and discoveries of this admirable Instrument?
Salv.If this succeed according to the progresse of other great inventions, it is to be hoped, that in processe of time, one may arrive to the sight of things, to us at present not to be imagined. But returning to our first discourse,Sixthly, The Earth and Moon interchangeably do illuminate. I say for the sixth resemblance betwixt the Moon and Earth, that as the Moon for a great part of time, supplies the want of the Suns light, and makes the nights, by the reflection of its own, reasonable clear; so the Earth, in recompence, affordeth it when it stands in most need, by reflecting the Solar rayes, a very cleer illumination, and so much, in my opinion, greater than that which cometh from her to us, by how much the superficies of the Earth is greater than that of the Moon.
Sagr.Hold there, Salviatus hold there, and permit me the pleasure of relating to you, how at this first hint I have penetrated the cause of an accident, which I have a thousand times thought upon,Light reflected from the Earth into the Moon. but could never find out. You would say, that the imperfect light which is seen in the Moon, especially when it is horned, comes from the reflection of the light of the Sun on the Superficies of the Earth and Sea; and that light is more clear, by how much the horns are lesse, for then the luminous part of the Earth, beheld by the Moon, is greater, according to that which was a little before proved; to wit, that the luminous part of the Earth, exposed to the Moon, is alway as great as the obscure part of the Moon, that is visible to the Earth; whereupon, at such time as the Moon is sharp-forked, and consequently its tenebrous part great, great also is the illuminated part of the Earth beheld from the Moon, and its reflection of light so much the more potent.
Salv.This is exactly the same with what I was about to say. In a word, it is a great pleasure to speak with persons judicious and apprehensive, and the rather to me, for that whilest others converse and discourse touching Axiomatical truths, I have many times creeping into my brain such arduous Paradoxes, that though I have a thousand times rehearsed this which you at the very first, have of your self apprehended, yet could I never beat it into mens brains.
Simpl.If you mean by your not being able to perswade them to it, that you could not make them understand the same, I much wonder thereat, and am very confident that if they did not understand it by your demonstration (your way of expression, being, in my judgment, very plain) they would very hardly have apprehended it upon the explication of any other man; but if you mean you have not perswaded them, so as to make them believe it, I wonder not, in the least, at this; for I confesse my self to be one of those who understand your discourses, but am not satisfied therewith; for there are in this, and some of the other six congruities, or resemblances, many difficulties, which I shall instance in, when you have gone through them all.
Salv.The desire I have to find out any truth, in the acquist whereof the objections of intelligent persons (such as your self) may much assist me, will cause me to be very brief in dispatching that which remains.Seventhly, The Earth and Moon do mutually eclipse. For a seventh conformity, take their reciprocal responsion as well to injuries, as favours; whereby the Moon, which very often in the height of its illumination, by the interposure of the Earth betwixt it and the Sun, is deprived of light, and eclipsed, doth by way of revenge, in like manner, interpose it self between the Earth and the Sun, and with its shadow obscureth the Earth; and although the revenge be not answerable to the injury, for that the Moon often continueth, and that for a reasonable long time, wholly immersed in the Earths shadow, but never was the Earth wholly, nor for any long time, eclipsed by the Moon; yet, neverthelesse, having respect to the smalnesse of the body of this, in comparision to the magnitude of the other, it cannot be denied but that the will and as it were valour of this, is very great. Thus much for their congruities or resemblances. It should next follow that we discourse touching their disparity; but because Simplicius will favour us with his objections against the former, its necessary that we hear and examine them, before we proceed any farther.
Sagr.And the rather, because it is to be supposed that Simplicius will not any wayes oppose the disparities, and incongruities betwixt the Earth and Moon, since that he accounts their substances extremely different.
Simpl.Amongst the resemblances by you recited, in the parallel you make betwixt the Earth and Moon, I find that I can admit none confidently save onely the first, and two others; I grant the first, namely, the spherical figure; howbeit, even in this there is some kind of difference, for that I hold that of the Moon to be very smooth and even, as a looking-glasse, whereas, we find and feel this of the Earth to be extraordinary montuous and rugged; but this belonging to the inequality of superficies, it shall be anon considered, in another of those Resemblances by you alledged; I shall therefore reserve what I have to say thereof, till I come to the consideration of that. Of what you affirm next, that the Moon seemeth, as you say in your second Resemblance, opacous and obscure in its self, like the Earth; I admit not any more than the first attribute of opacity, of which the Eclipses of the Sun assure me. For were the Moon transparent, the air in the total obscuration of the Sun, would not become so duskish, as at such a time it is, but by means of the transparency of the body of the Moon, a refracted light would passe through it, as we see it doth through the thickest clouds. But as to the obscurity, I believe not that the Moon is wholly deprived of light, as the Earth; nay, that clarity which is seen in the remainder ot its Discus, over and the above the small crescent enlightened by the Sun, I repute to be its proper and natural light, and not a reflection of the Earth,The second clarity of the Moon esteemed to be its native light. which I esteem unable, by reason of its asperity (cragginesse) and obscurity, to reflect the raies of the Sun. In the third Parallel I assent unto you in one part,The Earth unable to reflect the Suns raies. and dissent in another: I agree in judging the body of the Moon to be most solid and hard, like the Earth, yea much more; for if from Aristotle we receive that the Heavens are impenetrable,The substance of the Heavens impenetrable, according to Aristotle. and the Stars the most dense parts of Heaven, it must necessarily follow, that they are most solid and most impenetrable.
Sagr.What excellent matter would the Heavens afford us for to make Pallaces of, if we could procure a substance so hard and so transparent? Salv.Rather how improper, for being by its transparence, wholly invisible, a man would not be able without stumbling at the thresholds, and breaking his head against the Walls, to pass from room to room.
Sagr.This danger would not befall him,The substance of Heaven intangible. if it be true, as some Peripateticks say, that it is intangible: and if one cannot touch it, much less can it hurt him.
Salv.This would not serve the turn, for though the matter of the Heavens cannot be touch, as wanting tangible qualities: yet may it easily touch the elementary bodies; and to offend us it is as sufficient that it strike us, nay worse, than if we should strike it. But let us leave these Pallaces, or, to say better, these Castles in the air, and not interrupt Simplicius.
Simpl.The question which you have so casually started, is one of the most difficulty that is disputed in Philosophy; and I have on that subject most excellent conceits of a very learned Doctor of Padoua, but it is not now time to enter upon them. Therefore returning to our purpose, I say that the Moon, in my opinion, is much more solid than the Earth, but do not infer the same, as you do,The superficies of the Moon more sleek than any Looking-glaß. from the cragginess and montuousity of its superficies; but rather from the contrary, namely, from its aptitude to receive (as we see it experimented in the hardest stones) a polish and lustre exceeding that of the smoothest glass, for such necessarily must its superficies be, to render it apt to make so lively reflection of the Suns rays. And for those appearances which you mention, of Mountains, Cliffs, Hills, Valleys, &c. they are all illusions: and I have been present at certain publick disputes, where I have heard it strongly maintained against these introducers of novelties,The eminencies and cavities in the Moon are illusions of its opacous and perspicuous parts. that such appearances proceed from nothing else, but from the unequal distribution of the opacous and perspicuous parts, of which the Moon is inwardly and outwardly composed: as we see it often fall out in chrystal, amber, and many other precious stones of perfect lustre; in which by reason of the opacity of some parts, and the transparency of others, there doth appear several concavities and prominencies. In the fourth resemblance, I grant, that the superficies of Terrestrial Globe beheld from afar, would make two different appearances, namely, one more clear, the other more dark; but I believe that such diversity would succeed quite contrary to what you say; that is, I hold that the surface of the water would appear lucid, because that it is smooth and transparent; and that of the Earth would appear obscure, by reason of its opacity and scabrosity, ill accommodated for reflecting the light of the Sun. Concerning the fifth comparison, I grant it wholly, and am able, in case the Earth did shine as the Moon, to show the same to any one that should from thence above behold it, represented by figures answerable to those which we see in the Moon: I comprehend also, how the period of its illumination and variation of figure, would be monthly, albeit the Sun revolves round about it in twenty four hours: and lastly, I do not scruple to admit, that the half onely of the Moon seeth all the Earth, and that all the Earth seeth but onely half of the Moon. For what remains, I repute it most false, that the Moon can receive light from the Earth, which is most obscure, opacous, and utterly unapt to reflect the Suns light, as the Moon doth reflect it to us: and as I have said, I hold that that light which we see in the remainder of the Moons face (the splendid crescents subducted) by the illumination, is the proper and natural light of the Moon, and no easie matter would induce me to believe otherwise. The seventh, touching the mutual Eclipses, may be also admitted; howbeit that is wont to be called the eclipse of the Sun, which you are pleased to phrase the eclipse of the Earth. And this is what I have at this time to say in opposition to your seven congruities or resemblances, to which objections, if you are minded to make any reply, I shall willingly hear you.
Salv.If I have well apprehended what you have answered, it seems to me, that there still remains in controversie between us, certain conditions, which I made common betwixt the Moon & Earth, and they are these; You esteem the Moon to be smooth and polisht, as a Looking-glass, and as such, able to reflect the Suns light; and contrarily, the Earth, by reason of its montuosity, unable to make such reflection: You yield the Moon to be solid and hard, and that you argue from its being smooth and polite, and not from its being montuous; and for its appearing montuous, you assign as the cause, that it consists of parts more and less opacous and perspicuous. And lastly, you esteem that secondary light, to be proper to the Moon, and not reflected from the Earth; howbeit you seem not to deny the sea, as being of a smooth surface, some kind of reflection. As to the convincing you of that error, that the reflection of the Moon is made, as it were, like that of a Looking-glass, I have small hope, whilst I see, that what hath been read in the * Il Saggiatore, & Lettere Solari, two Treatises of Galilæus.* Saggiator and in the Solar Letters of our Common Friend, hath profited nothing in your judgment, if haply you have attentively read what he hath there written on this subject.
Simpl.I have perused the same so superficially, according to the small time of leasure allowed me from more solid studies; therefore, if you think you can, either by repeating some of those reasons, or by alledging others, resolve me these doubts, I will hearken to them attentively.
Salv.I will tell you what comes into my mind upon the instant, and its possible it may be a commixtion of my own conceipts, and those which I have sometime read in the fore-said Books, by which I well remember, that I was then perfectly satisfied, although the conclusions, at first sight seem'd unto me strange Paradoxes. We enquire Simplicius, whether to the making a reflection of light, like that which we receive from the Moon, it be necessary that the superficies from whence the reflection commeth, be so smooth and polite, as the face of a Looking-Glasse, or whether a superficies not smooth or polisht, but rough and uneven, be more apt for such a purpose. Now supposing two reflections should come unto us, one more bright, the other lesse, from two superficies opposite unto us, I demand of you, which of the two superficies you think would represent it self to our sight, to be the clearest, and which the obscurest.
Simpl.I am very confident, that that same, which most forcibly reflected the light upon me, would shew its self in its aspect the clearer, and the other darker.
Salv.Be pleased to take that Glasse which hangs on yonder Wall,It is proved at large that the Moons surface is sharp. and let us go out into the Court-yard. Come Sagredus. Now hang the glasse yonder, against that same Wall, on which the Sun shines, and now let us with-draw our selves into the shade. See yonder two superficies beaten by the Sun, namely, the Wall and the Glasse. Tell me now which appears clearest unto you, that of the Wall or that of the Glasse? Why do you not answer me?
Sagr.I leave the reply to Simplicius, who made the question; but I, for my own part, am perswaded upon this small beginning of the experiment, that the Moon must be of a very unpolisht surface.
Salv.What say you Simplicius, if you were to depaint that Wall, and that Glasse fastened unto it, where would you use your darkest colours, in designing the Wall, or else in painting the Looking-Glasse.
Simpl.Much the darker in depainting the Glasse.
Salv.Now if from the superficies, which represents it self more clear, there proceedeth a more powerful reflection of light, the Wall will more forcibly reflect the raies of the Sun, than the Glasse.
Simpl.Very well, Sir, have you ever a better experiment than this? you have placed us where the Glasses doth not reverberate upon us; but come along with me a little this way; how, will you not stir?
Sagr.You perhaps seek the place of the reflection, which the Glasse maketh.
Simpl.I do so.
Sagr.Why look you, there it is upon the opposite Wall, just as big as the Glasse, and little lesse bright than if the Sun had directly shined upon it.
Simpl.Come hither therefore, and see from hence the surface of the Glasse, and tell me whether you think it more obscure than that of the Wall.
Sagr.Look on it your self, for I have no mind at this time, to dazle my eyes; and I know very well, without seeing it, that it there appears as splendid and bright as the Sun it self, or little lesse.
Simpl.What say you therefore, is the reflection of a Glasse lesse powerful than that of a Wall? I see, that in this opposite Wall, where the reflection of the other illuminated Wall comes, together with that of the Glasse, this of the Glasse is much clearer; and I see likewise, that, from this place where I stand, the glasse it self appears with much more lustre than the Wall.
Salv.You have prevented me with your subtlety; for I stood in need of this very observation to demonstrate what remains. You see then the difference which happens betwixt the two reflections made by the two superficies of the Wall and Glasse, percu•t in the self-same manner, by the rayes of the Sun; and you see, how the reflection which comes from the Wall, diffuseth it self towards all the parts opposite to it, but that of the Glasse goeth towards one part onely, not at all bigger than the Glasse it self: you see likewise, how the superficies of the Wall, beheld from what part soever, alwayes shews it self of one and the same cleernesse, and every way, much clearer than that of the Glasse, excepting only in that little place, on which the Glasses reflection reverberates, for from thence indeed the Glasse appears much more lucid than the Wall. By these so sensible, and palpable experiments, my thinks one may soon come to know, whether the reflection which the Moon sends upon us, proceed as from a Glasse, or else, as from a Wall, that is, from a smooth superficies, or a rugged.
Sagr.If I were in the Moon it self, I think I could not with my hands more plainly feel the unevennesse of its superficies, than I do now perceive it, by apprehending your discourse. The Moon beheld in any posture, in respect of the Sun and us, sheweth us its superficies, touch't by the Suns rayes, alwayes equally clear; an effect, which answers to an hair that of the Wall, which beheld from what place soever, appeareth equally bright, and differeth from the Glasse, which from one place onely appeareth lucid, and from all others obscure. Moreover, the light which cometh to me from the reflection of the Wall, is tollerable, and weak, in comparison of that of the Glasse, which is little lesse forcible and offensive to the sight, than that primary and direct light of the Sun. And thus without trouble do we behold the face of the Moon; which were it as a Glasse, it appearing to us by reason of its vicinity, as big as the Sun it self, its splendor would be absolutely intollerable, and would seem as if we beheld another Sun.
Salv.Ascribe not, I beseech you Sagredus, more to my demonstration, than it produceth. I will oppose you with an instance, which I see not well how you can easily resolve. You insist upon it as a grand difference between the Moon and Glasse, that it emits its reflection towards all parts equally, as doth the Wall; whereas the Glasse casts it upon one onely determinate place; and from hence you conclude the Moon to be like to the Wall, and not to the Glasse:Flat Looking-glasses cast forth the reflection towards but one place, but the spherical every way. But I must tell you, that that same Glasse casts its reflection on one place onely, because its surface is flat, and the reflex rayes being to depart at angles equal to those of the rayes of incidence, it must follow that from a plane or flat superficies, they do depart unitedly towards the same place; but in regard that the superficies of the Moon is not plain, but spherical, and the incident rayes upon such a superficies, being to reflect themselves at angles equal to those of the incidence towards all parts, by means of the infinity of the inclinations which compose the spherical superficies, therefore the Moon may send forth its reflection every way; and there is no necessity for its repercussion upon one place onely, as that Glasse which is flat.
Simpl.This is one of the very same objections, which I intended to have made against him.
Sagr.If this be one, you had need have more of them; yet I tell you, that as to this first, it seems to me to make more against you, than for you.
Simpl.You have pronounced as a thing manifest, that the reflection made by that Wall, is as cleer and lucid as that which the Moon sends forth, and I esteem it nothing in comparison thereto. For, in this businesse of the illumination, its requisite to respect, and to distinguish the Sphere of Activity;The sphere of Activity greater in the Cœlestial bodies than in Elementary. and who questions but the Cœlestial bodies have greater Spheres of activity, than these our elementary, frail, and mortal ones? and that Wall, finally, what else is it but a little obscure Earth, unapt to shine?
Sagr.And here also I believe, that you very much deceive your felf. But I come to the first objection moved by Salviatus; and I consider, that to make a body appear unto us luminous, it sufficeth not that the rayes of the illuminating body fall upon it, but it is moreover requisite that the reflex rayes arrive to our eye; as is manifestly seen in the example of that Glasse, upon which, without question, the illuminating rayes of the Sun do come; yet neverthelesse, it appears not to us bright and shining, unlesse we set our eye in that particular place, where the reflection arriveth. Now let us consider what would succeed, were the glasse of a spherical figure; for without doubt, we should find, that of the reflection made by the whole surface illuminated, that to be but a very small part, which arriveth to the eye of a particular beholder; by reason that that is but an inconsiderable particle of the whole spherical superficies, the inclination of which casts the ray to the particular place of the eye; whence the part of the spherical superficies, which shews it self shining to the eye, must needs be very small; all the rest being represented obscure. So that were the Moon smooth, as a Looking-glasse,The Moon if it were smooth, like a spherical glasse, would be invisible. a very small part would be seen by any particular eye to be illustrated by the Sun, although its whole Hemisphere were exposed to the Suns rayes; and the rest would appear to the eye of the beholder as not illuminated, and therefore invisible; and finally, the whole Moon would be likewise invisible, for so much as that particle, whence the reflection should come, by reason of its smalnesse and remotenesse, would be lost. And as it would be invisible to the eye, so would it not afford any light; for it is altogether impossible, that a bright body should take away our darknesse by its splendor, and we not to see it.
Salv.Stay good Sagredus, for I see some emotions in the face and eyes of Simplicius, which are to me as indices that he is not either very apprehensive of, or satisfied with this which you, with admirable proof, and absolute truth have spoken. And yet I now call to mind, that I can by another experiment remove all scruple. I have seen above in a Chamber, a great spherical Looking-glasse; let us send for it hither, and whilest it is in bringing, let Simplicius return to consider, how great the clarity is which cometh to the Wall here, under the penthouse, from the reflection of the flat glasse.
Simpl.I see it is little lesse shining, than if the Sun had directly beat upon it.
Salv.So indeed it is. Now tell me, if taking away that small flat glasse, we should put that great spherical one in the same place, what effect (think you) would its reflection have upon the same Wall?
Simpl.I believe that it would eject upon it a far greater and more diffused light.
Salv.But if the illumination should be nothing, or so small, that you would scarse discern it, what would you say then?
Simpl.When I have seen the effect, I will bethink my self of an answer.
Salv.See here is the glasse, which I would have to be placed close to the other. But first let us go yonder towards the reflection of that flat one, and attentively observe its clarity; see how bright it is here where it shines, and how distinctly one may discern these small unevennesses in the Wall.
Simpl.I have seen and very well observed the same, now place the other glasse by the side of the first.
Salv.See where it is. It was placed there assoon as you began to look upon the Walls small unevennesses, and you perceived it not, so great was the encrease of the light all over the rest of the Wall. Now take away the flat glasse. Behold now all reflection removed, though the great convex glasse still remaineth. Remove this also, and place it there again if you please, and you shall see no alteration of light in all the Wall. See here then demonstrated to sense, that the reflection of the Sun, made upon a spherical convex glasse, doth not sensibly illuminate the places neer unto it. Now what say you to this experiment?
Simpl.I am afraid that there may be some Leigerdemain, used in this affair; yet in beholding that glasse I see it dart forth a great splendor, which dazleth my eyes; and that which imports most of all, I see it from what place soever I look upon it; and I see it go changing situation upon the superficies of the glasse, which way soever I place my self to look upon it; a necessary argument, that the light is livelily reflected towards every side, and consequently, as strongly upon all that Wall, as upon my eye.
Salv.Now you see how cautiously and reservedly you ought to proceed in lending your assent to that, which discourse alone representeth to you. There is no doubt but that this which you say, carrieth with it probability enough, yet you may see, how sensible experience proves the contrary.
Simpl.How then doth this come to pass?
Salv.I will deliver you my thoughts thereof, but I cannot tell how you may be pleas'd therewith. And first, that lively splendor which you see upon the glass, and which you think occupieth a good part thereof, is nothing near so great, nay is very exceeding small; but its liveliness occasioneth in your eye, (by means of the reflection made on the humidity of the extream parts of the eye-brows, which distendeth upon the pupil) an adventitious irradiation, like to that blaze which we think we see about the flame of a candle placed at some distance; or if you will, you may resemble it to the adventitious splendor of a star;The small body of the stars fringed round about with rays, appeareth very much bigger than plain and naked, and in its native clarity. for if you should compare the small body v. g. of the Canicula, seen in the day time with the Telescope, when it is seen without such irradiation, with the same seen by night by the eye it self, you will doubtless comprehend that being irradiated, it appeareth above a thousand times bigger than the naked and real body: and a like or greater augmentation doth the image of the Sun make, which you see in that glass. I say greater, for that it is more lively than the star, as is manifest from our being able to behold the star with much less offence, than this reflection of the glass. The reverberation therefore which is to dispere it self all over this wall, cometh from a small part of that glass, and that which even now came from the whole flat glass dispersed and restrain'd it self to a very small part of the said wall. What wonder is it then, that the first reflection very lively illuminates, and that this other is almost imperceptible?
Simpl.I find my self more perplexed than ever, and there presents it self unto me the other difficulty, how it can be that that wall, being of a matter so obscure, and of a superficies so unpolish'd, should be able to dart from it greater light, than a glass very smooth and polite.
Salv.Greater light it is not, but more universal; for as to the degree of brightness, you see that the reflection of that small flat glass, where it beamed forth yonder under the shadow of the penthouse, illuminateth very much; and the rest of the wall which receiveth the reflection of the wall on which the glass is placed, is not in any great measure illuminated, as was the small part on which the reflection of the glass fell. And if you would understand the whole of this business, you must consider that the superficies of that wall's being rough,The reflex light of uneven bodies, is more universal than that of the smooth, & why. is the same as if it were composed of innumerable small superficies, disposed according to innumerable diversities of inclinations: amongst which it necessarily happens, that there are many disposed to send forth their reflex rays from them into such a place, many others into another: and in sum, there is not any place to which there comes not very many rays, reflected from very many small superficies, dispersed throughout the whole superficies of the rugged body, upon which the rays of the Sun fall. From which it necessarily followeth, That upon any, whatsoever, part of any superficies, opposed to that which receiveth the primary incident rays, there is produced reflex rays, and consequently illumination. There doth also follow thereupon, That the same body upon which the illuminating rays fall, beheld from whatsoever place, appeareth all illuminated and shining: and therefore the Moon, as being of a superficies rugged and not smooth,The Moon, if it were smooth and sleek, would be invisible. beameth forth the light of the Sun on every side, and to all beholders appeareth equally lucid. But if the surface of it, being spherical, were also smooth as a glass, it would become wholly invisible; forasmuch as that small part, from which the image of the Sun should be reflected unto the eye of a particular person, by reason of its great distance would be invisible, as I have said before.
Simpl.I am very apprehensive of your discourse; yet methinks I am able to resolve the same with very little trouble; and easily to maintain, that the Moon is rotund and polite, and that it reflects the Suns light unto us in manner of a glass; nor therefore ought the image of the Sun to be seen in the middle of it, "forasmuch as the species of the Sun it self admits not its small figure to be seen at so great a distance, but the light produced by the Sun may help us to conceive that it illuminateth the whole Lunar Body: a like effect we may see in a plate gilded and well pollish'd, which touch't by a luminous body, appeareth to him that beholds it at some distance to be all shining; and onely near at hand one may discover in the middle of it the small image of the luminous body".
Salv.Ingenuously confessing my dullness of apprehension, I must tell you, that I understand not any thing of this your discourse, save onely what concerns the gilt plate: and if you permit me to speak freely, I have a great conceit that you also understand not the same, but have learnt by heart those words written by some one out of a desire of contradiction, and to shew himself more intelligent than his adversary; but it must be to those, which to appear also more wise, applaud that which they do not understand, and entertain a greater conceit of persons, the less they are by them understood: and the writer himself may be one of those (of which there are many) who write what they do not understand,Some write what they understand not, and therefore understand not what they write. and consequently understand not what they write. Therefore, omitting the rest, I reply, as to the gilt plate, that if it be flat and not very big, it may appear at a distance very bright, whilst a great light beameth upon it, but yet it must be when the eye is in a determinate line, namely in that of the reflex rays: and it will appear the more shining, if it were v. g. of silver, by means of its being burnished, and apt through the great density of the metal, to receive a perfect polish. And though its superficies, being very well brightned, were not exactly plain, but should have various inclinations, yet then also would its splendor be seen many ways; namely, from as many places as the various reflections, made by the several superficies,Diamonds ground to divers sides, & why. do reach: for therefore are Diamonds ground to many sides, that so their pleasing lustre might be beheld from many places. But if the Plate were very big, though it should be all plain, yet would it not at a distance appear all over shining: and the better to express my self, Let us suppose a very large gilt plate exposed to the Sun, it will shew to an eye far distant, the image of the Sun, to occupy no more but a certain part of the said plate; to wit, that from whence the reflection of the incident solar rays come: but it is true that by the vivacity of the light, the said image will appear fringed about with many rays, and so will seem to occupie a far greater part of the plate, than really it doth. And to shew that this is true, when you have noted the particular place of the plate from whence the reflection cometh, and conceived likewise how great the shining place appeared to you, cover the greater part of that same space, leaving it only visible about the midst; and all this shall not any whit diminish the apparent splendor to one that beholds it from afar; but you shall see it largely dispers'd upon the cloth or other matter, wherewith you covered it. If therefore any one, by seeing from a good distance a small gilt plate to be all over shining, should imagine that the same would also even in a plate as broad as the Moon, he is no less deceived, than if he should believe the Moon to be no bigger than the bottom of a tub. If again the plate were turn'd into a spherical superficies, the reflection would be seen strong in but one sole particle of it; but yet by reason of its liveliness, it will appear fringed about with many glittering rays: the rest of the Ball would appear according as it was burnished;Silver burnished appears more obscure, than the not burnished, & why. and this also onely then when it was not very much polished, for should it be perfectly brightned, it would appear obscure. An example of this we have dayly before our eyes in silver vessels, which whilst they are only boyl'd in the Argol and Salt, they are all as white as snow, and do not reflect any image; but if they be in any part burnish'd, they become in that place presently obscure: and in them one may see the representation of any thing as in Looking-glasses. And that chanto obscurity, proceeds from nothing else but the smoothing and plaining of a fine grain, which made the superficies of the silver rough, and yet such, as that it reflected the light into all parts, whereby it seemed from all parts equally illuminated: which small unevennesses, when they come to be exquisitely plained by the burnish, so that the reflection of the rays of incidence are all directed unto one determinate place; then, from that same place, the burnish'd part shall shew much more bright and shining than the rest which is onely whitened by boyling; but from all other places it looks very obscure. And note, that the diversity of sights of looking upon burnish'd superficies,Burnish'd Steel beheld from one place appears very bright, and from another, very obscure. occasioneth such difference in appearances, that to imitate and represent in picture, v. g. a polish'd Cuirace, one must couple black plains with white, one sideways to the other, in those parts of the arms where the light falleth equally.
Sagr.If therefore these great Philosophers would acquiese in granting, that the Moon, Venus and the other Planets, were not of so bright and smooth a surface as a Looking-glass, but wanted some small matter of it, namely, were as a silver plate, onely boyled white, but not burnished; would this yet suffice to the making of it visible, and apt for darting forth the light of the Sun?
Salv.It would suffice in part; but would not give a light so strong, as it doth being mountainous, and in sum, full of eminencies and great cavities. But these Philosophers will never yield it to be lesse polite than a glasse; but far more, if more it can be imagined; for they esteeming that to perfect bodies perfect figures are most sutable; it is necessary, that the sphericity of those Cœlestial Globes be most exact; besides, that if they should grant me some inequality, though never so small, I would not scruple to take any other greater; for that such perfection consisting in indivisibles, an hair doth as much detract from its perfection as a mountain.
Sagr.Here I meet with two difficulties, one is to know the reason why the greater inequality of superficies maketh the stronger reflection of light; the other is, why these Peripatetick Gentlemen are for this exact figure.
Salv.I will answer to the first;The more rough superficies make greater reflection of light, than the less rough. and leave to Simplicius the care of making reply to the second. You must know therefore, that the same superficies happen to be by the same light more or less illuminated, according as the rayes of illumination fall upon them more or lesse obliquely;Perpendicular rays illuminate more than the oblique, and why. so that the greatest illumination is where the rayes are perpendicular. And see, how I will prove it to your sense. I bend this paper, so, that one part of it makes an angle upon the other: and exposing both these parts to the reflection of the light of that opposite Wall, you see how this side which receiveth the rayes obliquely, is lesse shining than this other, where the reflection fals at right angles; and observe, that as I by degrees receive the illumination more obliquely, it groweth weaker.
Sagr.I see the effect, but comprehend not the cause.
Salv.If you thought upon it but a minute of an hour, you would find it; but that I may not waste the time, see a kind of demonstration thereof in Fig. 7.
Sagr.The bare sight of this Figure hath fully satisfied me, therefore proceed.
Simpl.Pray you let me hear you out, for I am not of so quick an apprehension.
Salv.Fancie to your self, that all the paralel lines, which you see to depart from the terms A. B. are the rays which fall upon the line C. D. at right angles:The more oblique Rayes illuminate leß, and why. then incline the said C. D. till it hang as D. O. now do not you see that a great part of those rays which peirce C. D. pass by without touching D. O? If therefore D. O. be illuminated by fewer rays, it is very reasonable, that the light received by it be more weak. Let us return now to the Moon, which being of a spherical figure, if its superficies were smooth, as this paper, the parts of its hemisphere illuminated by the Sun, which are towards its extremity, would receive much less light, than the middle parts; the rays falling upon them most obliquely, and upon these at right angles; whereupon at the time of full Moon, when we see almost its whole Hemisphere illuminated, the parts towards the midst, would shew themselves to us with more splendor, than those others towards the circumference: which is not so in effect. Now the face of the Moon being represented to me full of indifferent high mountains, do not you see how their tops and continuate ridges, being elevated above the convexity of the perfect spherical superficies, come to be exposed to the view of the Sun, and accommodated to receive its rays much less obliquely, and consequently to appear as luminous as the rest?
Sagr.All this I well perceive: and if there are such mountains, its true, the Sun will dart upon them much more directly than it would do upon the inclination of a polite superficies: but it is also true, that betwixt those mountains all the valleys would become obscure, by reason of the vast shadows, which in that time would be cast from the mountains, whereas the parts towards the middle, though full of valleys and hills, by reason they have the Sun elevated, would appear without shadow, and therefore more lucid by far than the extreme parts, which are no less diffused with shadow than light, and yet we can perceive no such difference.
Simpl.I was ruminating upon the like difficulty.
Salv.How much readier is Simplicius to apprehend the objections which favour the opinions of Aristotle, than their solutions? I have a kind of suspition, that he strives also sometimes to dissemble them; and in the present case, he being of himself able to hit upon the doubt, which yet is very ingenious, I cannot believe but that he also was advis'd of the answer; wherefore I will attempt to wrest the same (as they say) out of his mouth. Therefore tell me, Simplicius, do you think there can be any shadow, where the rays of the Sun do shine?
Simpl.I believe, nay I am certain that there cannot; for that it being the grand luminary, which with its rays driveth away darkness, it is impossible any tenebrosity should remain where it cometh; moreover, we have the definition, that Tenebræ sunt privatio luminis.
Salv.Therefore the Sun, beholding the Earth, Moon or other opacous body, never seeth any of its shady parts, it not having any other eyes to see with, save its rays, the conveyers of light: and consequently, one standing in the Sun would never see any thing of umbrage, forasmuch as his visive rays would ever go accompanied with those illuminating beams of the Sun.
Simpl.This is true, without any contradiction.
Salv.But when the Moon is opposite to the Sun, what difference is there between the tract of the rayes of your sight, and that motion which the Suns rayes make?
Simpl.Now I understand you; for you would say, that the rayes of the sight and those of the Sun, moving by the same lines, we cannot perceive any of the obscure valleys of the Moon. Be pleased to change this your opinion, that I have either simulation or dissimulation in me; for I protest unto you, as I am a Gentleman, that I did not guesse at this solution, nor should I have thought upon it, without your help, or without long study.
Sagr.The resolutions, which between you two have been alledged touching this last doubt, hath, to speak the truth, satisfied me also. But at the same time this consideration of the visible rayes accompanying the rayes of the Sun, hath begotten in me another scruple, about the other part, but I know not whether I can expresse it right, or no: for it but just now comming into my mind, I have not yet methodized it to my mind: but let us see if we can, all together, make it intelligible. There is no question, but that the parts towards the circumference of that polish't, but not burnish't Hemisphere, which is illuminated by the Sun, receiving the rayes obliquely, receive much fewer thereof, than the middlemost parts, which receive them directly. And its possible, that a tract or space of v. g. twenty degrees in breadth, and which is towards the extremity of the Hemisphere, may not receive more rays than another towards the middle parts, of but four degree broad: so that that doubtless will be much more obscure than this; and such it will appear to whoever shall behold them both in the face, or (as I may say) in their full magnitude. But if the eye of the beholder were constituted in such a place, that the breadth of the twenty degrees of the obscure space, appeared not to it longer than one of four degrees, placed in the midst of the Hemisphere, I hold it not impossible for it to appear to the said beholder equally clear and lucid with the other; because, finally, between two equal angles, to wit, of four degrees apiece, there come to the eye the reflections of two equal numbers of rayes: namely, those which are reflected from the middlemost space, four degrees in breadth, and those reflected from the other of twenty degrees, but seen by compression, under the quantity of four degrees: and such a situation shall the eye obtain, when it is placed between the said Hemisphere, and the body which illuminates it; for then the sight and rayes move in the same lines. It seemeth not impossible therefore, but that the Moon may be of a very equal superficies; and that neverthelesse, it may appear when it is at the full, no less light in the extremities, than in the middle parts.
Salv.The doubt is ingenious and worthy of consideration; and as it but just now came into your mind unawares, so I will like wise answer with what first comes into my thoughts, and it may happily fall out, that by thinking more upon it, I may stumble upon a better reply. But before, that I labyrinth my self any farther, it would be necessary, that we assure our selves by some experiment, whether your objection prove in effect, what it seemeth to conclude in appearance; and therefore taking once more the same paper, and making it to incline, by bending a little part thereof upon the remainder, let us try whether exposing it to the Sun, so that the rayes of light fall upon the lesser part directly, and upon the other obliquely; this which receiveth the rayes directly appeareth more lucid; and see here by manifest experience, that it is notably more clear. Now if your objection be conclusive, it will follow, that stooping with our eye so, that in beholding the other greater part, less illuminated, in compression or fore-shortning, it appear unto us no bigger than the other, more shining; and that consequently, it be not beheld at a greater angle than that; it will necessarily ensue, I say, that its light be encreased, so that it do seem to us as bright as the other. See how I behold, and look upon it so obliquely, that it appeareth to me narrower than the other; but yet, notwithstanding its obscurity, doth not to my perceiving, at all grow clearer. Try now if the same succeed to you.
Sagr.I have look't upon it, and though I have stooped with my eye, yet cannot I see the said superficies encrease in light or clarity; nay me thinks it rather grows more dusky.
Salv.We are hitherto confident of the invalidity of the objection; In the next place, as to the solution, I believe, that, by reason the Superficies of this paper is little lesse than smooth, the rayes are very few, which be reflected towards the point of incidence, in comparison of the multitude, which are reflected towards the opposite parts; and that of those few more and more are lost, the nearer the visive rayes approach to those lucid rayes of incidence; and because it is not the incident rayes, but those which are reflected to the eye, that make the object appear luminous; therefore, in stooping the eye, there is more lost than got, as you your self confesse to have seen in looking upon the obscurer part of the paper.
Sagr.I rest satisfied with this experiment and reason: It remains now, that Simplicius answer to my other question, and tell me what moves the Peripateticks to require this so exact rotundity in the Cœlestial bodies.
Simpl.The Cœlestial bodies being ingenerable, inalterable, impassible, immortal,&c.Perfect sphericity why ascribed to Cœlestial bodies, by the Peripateticks. they must needs be absolutely perfect; and their being absolute perfect, necessarily implies that there is in them all kinds of perfection; and consequently, that their figure be also perfect, that is to say, spherical; and absolutely and perfectly spherical, and not rough and irregular.
Salv.And this incorruptibility, from whence do you prove it?
Simpl.Immediately by its freedom from contraries, and mediately, by its simple circular motion.
Salv.So that;The Figure is not the cause of incorruptibility, but of longer duration. by what I gather from your discourse, in making the essence of the Cœlestial bodies to be incorruptible, inalterable, &c, there is no need of rotundity as a cause, or requisite; for if this should cause inalterability, we might at our pleasure make wood, wax, and other Elementary matters, incorruptible, by reducing them to a spherical figure.
Simpl.And is it not manifest that a ball of Wood will better and longer be preserved, than an oblong, or other angular figure, made of a like quantity of the same wood.
Salv.This is most certain, but yet it doth not of corruptible become incorruptible, but still remains corruptible, though of a much longer duration.Corruptibility admits of more or lesse; so doth not incorruptibiliiy. Therefore you must note, that a thing corruptible, is capable of being more or lesse such, and we may properly say this is lesse corruptible than that; as for example, the Jasper, than the Pietra Sirena; but incorruptibility admits not of more, or lesse, so as that it may be said this is more incorruptible than that,The perfection of figure, operateth in corruptible bodies, but not in the eternal. if both be incorruptible and eternal. The diversity of figure therefore cannot operate: save onely in matters capable of more or lesse duration; but in the eternal, which cannot be other than equally eternal, the operation of figure ceaseth. And therefore, since the Cœlestial matter is not incorruptible by figure, but otherwayes no man needs to be so solicitous for this perfect sphericity; for if the matter be incorruptible, let it have what figure it will, it shall be alwayes such.
Sagr.But I am considering another thing,If the spherical figure conferreth eternity, all bodies would be eternal. and say, that if we should grant the spherical figure a faculty of conferring incorruptibility, all bodies of whatsoever figure, would be incorruptible; forasmuch as if the rotund body be incorruptible, corruptibility would then subsist in those parts which alter the perfect rotundity; as for instance, there is in a Die a body perfectly round, and, as such, incorruptible; therefore it remaineth that those angles be corruptible which cover and hide the rotundity; so that the most that could happen, would be, that those angles, and (to so speak) excrescencies, would corrupt. But if we proceed to a more inward consideration, that in those parts also towards the angles, there are comprised other lesser bals of the same matter; and therefore they also, as being round, must be also incorruptible; and likewise in the remainders, which environ these eight lesser Spheres, a man may understand that there are others: so that in the end, resolving the whole Die into innumerable balls, it must necessarily be granted incorruptible. And the same discourse and resolution may be made in all other figures.
Salv.Your method in making the conclusion, for if v. g. a round Chrystal were, by reason of its figure, incorruptible; namely, received from thence a faculy of resisting all internal and external alterations, we should not find, that the joyning to it other Chrystal, and reducing it v. g. into a Cube, would any whit alter it within, or without; so as that it would thereupon become lesse apt to resist the new ambient, made of the same matter, than it was to resist the other, of a matter different; and especially, if it be true, that corruption is generated by contraries, as Aristotle saith; and with what can you enclose that ball of Crystal, that is lesse contrary to it, than Crystal it self? But we are not aware how time flies away; and it will be too late before we come to an end of our dispute, if we should make so long discourses, upon every particular; besides our memories are so confounded in the multiplicity of notions, that I can very hardly recal to mind the Propotsiions, which I proposed in order to Simplicius, for our consideration.
Simpl.I very well remember them: And as to this particular question of the montuosity of the Moon, there yet remains unanswered that which I have alledged, as the cause, (and which may very well serve for a solution) of that Phænomenon, saying, that it is an illusion proceeding from the parts of the Moon, being unequally opacous, and perspicuous.
Sagr.Even now, when Simplicius ascribed the apparent Protnberancies or unevennesses of the Moon (according to the opinion of a certain Peripatetick his friend) to the diversly opacous, and perspicuous parts of the said Moon,Mother of Pearl accommodated to imitate the apparent unevennesses of the Moons surface. conformable to which the like illusions are seen in Crystal, and Jems of divers kinds, I bethought my self of a matter much more commodious for the representing such effects; which is such, that I verily believe, that that Philosopher would give any price for it; and it is the mother of Pearl, which is wrought into divers figures, and though it be brought to an extreme evennesse, yet it seemeth to the eye in several parts, so variously hollow and knotty, that we can scarce credit our feeling of their evennesse.
Salv.This invention is truly ingenious; and that which hath not been done already, may be done in time to come; and if there have been produced other Jems, and Crystals, which have nothing to do with the illusions of the mother of Pearl, these may be produced also; in the mean time, that I may not prevent any one, I will suppresse the answer which might be given, and onely for this time betake my self to satisfie the objections brought by Simplicius. I say therefore, that this reason of yours is too general, and as you apply it not to all the appearances one by one; which are seen in the Moon, and for which my self and others are induced to hold it mountainous, I believe you will not find any one that will be satisfied with such a doctrine; nor can I think, that either you, or the Author himself, find in it any greater quietude,The apparent unevennesses of the Moon cannot be imitated by way of more and less opacity & perspicuity. than in any other thing wide from the purpose. Of the very many several appearances which are seen night by night in the course of Moon, you cannot imitate so much as one, by making a Ball at your choice, more or less opacous and perspicuous, and that is of a polite superficies;The various aspects of the Moon, imitable with any opacous matter. whereas on the contrary, one may make Balls of any solid matter whatsoever, that is not transparent, which onely with eminencies and cavities, and by receiving the illumination several ways, shall represent the same appearances and mutations to an hair,Various appearances from which the Moons montuosity is argued. which from hour to hour are discovered in the Moon. In them you shall see the ledges of Hills exposed to the Suns light, to be very shining, and after them the projections of their shadows very obscure; you shall see them greater and less, according as the said eminencies shall be more or less distant from the confines which distinguish the parts of the Moon illuminated, from the obscure: you shall see the same term and confine, not equally distended, as it would be if the Ball were polish'd, but craggie and rugged. You shall see beyond the same term, in the dark parts of the Moon many bright prominencies, and distinct from the rest of the illuminations: you shall see the shadows aforesaid, according as the illumination gradually riseth, to deminish by degrees, till they wholly disappear; nor are there any of them to be seen when the whole Hemisphere is enlightned. Again on the contrary, in the lights passage towards the other Hemisphere of the Moon, you shall again observe the same eminencies that were marked, and you shall see the projections of their shadows to be made a contrary way, and to decrease by degrees: of which things, once more I say, you cannot shew me so much as one in yours that are opacous and perspicuous.
Sagr.One of them certainly he may imitate, namely, that of the Full-Moon, when by reason of its being all illuminated, there is not to be seen either shadow, or other thing, which receiveth any alteration from its eminencies and cavities. But I beseech you, Salviatus, let us spend no more time on this Argument, for a person that hath had but the patience to make observation of but one or two Lunations, and is not satisfied with this most sensible truth, may well be adjudged void of all judgment; and upon such why should we throw away our time and breath in vain?
Simpl.I must confess I have not made the observations, for that I never had so much curiosity, or the Instruments proper for the business; but I will not fail to do it. In the mean time, we may leave this question in suspense, and pass to that point which follows, producing the motives inducing you to think that the Earth may reflect the light of the Sun no less forceably than the Moon, for it seems to me so obscure and opacous, that I judg such an effect altogether impossible.
Salv.The cause for which you repute the Earth unapt for illumination, may rather evince the contrary: And would it not be strange, Simplicius, if I should apprehend your discourses better than you your self?
Simpl.Whether I argue well or ill, it may be, that you may better understand the same than I; but be it ill or well that I discourse, I shall never believe that you can penetrate what I mean better than I my self.
Salv.Well, I will make you believe the same presently. Tell me a little, when the Moon is near the Full, so that it may be seen by day, and also at midnight, at what do you think it more splendid, by day or by night?
Simpl.By night,The Moon beheld in the day time, is like to a little cloud. without all comparison. And methinks the Moon resembleth that pillar of Clouds and pillar of Fire, which guided the Israelites; which at the presence of the Sun, appeared like a Cloud, but in the night was very glorious. Thus I have by day observed the Moon amidst certain small Clouds,The Moon appears brighter by night than by day. just as if one of them had been coloured white, but by night it shines with much splendor.
Salv.So that if you had never happened to see the Moon, save onely in the day time, you would not have thought it more shining than one of those Clouds.
Simpl.I verily believe I should not.
Salv.Tell me now; do you believe that the Moon is really more shining in the night than day, or that by some accident it seemeth so?
Simpl.I am of opinion, that it resplends in it self as much in the day as night, but that its light appears greater by night, because we behold it in the dark mantle of Heaven; and in the day time, the whole Atmosphere being very clear, so that she little exceedeth it in lustre, she seems to us much less bright.
Salv.Now tell me; have you ever at midnight seen the Terrestrial Globe illuminated by the Sun?
Simpl.This seemeth to me a question not to be ask'd, unless in jest, or of some person known to be altogether void of sense.
Salv.No, no; I esteem you to be a very rational man, and do ask the question seriously; and therefore answer me: and if afterwards you shall think that I speak impertinently, I will be content to be the senseless man: for he is much more a fool who interrogates simply, than he to whom the question is put.
Simpl.If then you do not think me altogether simple, take it for granted that I have answered you already, and said, that it is impossible, that one that is upon the Earth, as we are, should see by night that part of the Earth where it is day, namely, that is illuminated by the Sun.
Salv.Therefore you have never seen the Earth enlightned, save onely by day; but you see the Moon to shine also in the dead of night. And this is the cause, Simplicius, which makes you believe that the Earth doth not shine like the Moon; but if you could see the Earth illuminated, whilst you were in some dark place, like our night, you would see it shine brighter than the Moon. Now if you desire that the comparison may proceed well, you must compare the light of the Earth, with that of the Moon seen in the day time, and not with the same by night: for it is not in our power to see the Earth illuminated, save onely in the day. Is it not so?
Simpl.So it ought to be.
Salv.And forasmuch as you your self have already confessed to have seen the Moon by day among some little white Clouds, and very nearly, as to its aspect, resembling one of them; you did thereby grant,Clouds are no less apt than the Moon to be illuminated by the Sun. that those Clouds, which yet are Elementary matters, are as apt to receive illumination, as the Moon, yea more, if you will but call to mind that you have sometimes seen some Clouds of vast greatness, and as perfect white as the Snow; and there is no question, but that if such a Cloud could be continued so luminous in the deep of night, it would illuminate the places near about it, more than an hundred Moons. If therefore we were assured that the Earth is illuminated by the Sun, like one of those Clouds, it would be undubitable, but that it would be no less shining than the Moon. But of this there is no question to be made, in regard we see those very Clouds in the absence of the Sun, to remain by night, as obscure as the Earth: and that which is more, there is not any one of us, but hath seen many times some such Clouds low, and far off, and questioned whether they were Clouds or Mountains: an evident sign that the Mountains are no less luminous than those Clouds.A wall illuminated by the Sun, compared to the Moon shineth no less than it.
Sagr.But what needs more discourse? See yonder the Moon is risen, and more than half of it illuminated; see there that wall, on which the Sun shineth; retire a little this way, so that you see the Moon sideways with the wall: look now; which of them shews more lucid? Do not you see, that if there is any advantage, the wall hath it? The Sun shineth on that wall; from thence it is reverberated upon the wall of the Hall,The third reflection of a Wall illuminates more than the first of the Moon. from thence it's reflected upon that chamber, so that it falls on it at the third reflection: and I am very certain, that there is in that place more light, than if the Moons light had directly faln upon it.
Simpl.But this I cannot believe; for the illumination of the Moon, especially when it is at the full, is very great.
Sagr.It seemeth great by reason of the circumjacent dark places;The light of the Moon weaker than that of the twilight. but absolutely it is not much, and is less than that of the twilight half an hour after the Sun is set; which is manifest, because you see not the shadows of the bodies illuminated by the Moon till then, to begin to be distinguished on the Earth. Whether, again, that third reflection upon that chamber, illuminates more than the first of the Moon, may be known by going thether, and reading a Book, and afterwards standing there in the night by the Moons light, which will shew by which of them lights one may read more or less plainly, but I believe without further tryal, that one should see less distinctly by this later.
Salv.Now, Simplicius, (if haply you be satisfied) you may conceive, as you your self know very well, that the Earth doth shine no less than the Moon; and the only remembring you of some things, which you knew of your self, and learn'd not of me, hath assured you thereof: for I taught you not that the Moon shews lighter by night than by day, but you understood it of your self; as also you could tell me that a little Cloud appeareth as lucid as the Moon: you knew also, that the illumination of the Earth cannot be seen by night; and in a word, you knew all this, without knowing that you knew it. So that you have no reason to be scrupulous of granting, that the dark part of the Earth may illuminate the dark part of the Moon, with no less a light than that wherewith the Moon illuminates the obscurities of the night, yea rather so much the greater, inasmuch as the Earth is forty times bigger than the Moon.
Simpl.I must confess that I did believe, that that secondary light had been the natural light of the Moon.
Salv.And this also you know of your self, and perceive not that you know it. Tell me, do not you know without teaching, that the Moon shews it self more bright by night than by day,Luminous bodies appear the brighter in an obscurer ambient. in respect of the obscurity of the space of the ambient? and consequently, do you not know in genere, that every bright body shews the clearer, by how much the ambient is obscurer?
Simpl.This I know very well.
Salv.When the Moon is horned, and that secondary light seemeth to you very bright, is it not ever nigh the Sun, and consequently, in the light of the crepusculum, (twilight?)
Simpl.It is so; and I have oftentimes wish'd that the Air would grow thicker, that I might be able to see that same light more plainly; but it ever disappeared before dark night.
Salv.You know then very certainly, that in the depth of night, that light would be more conspicuous.
Simpl.I do so; and also more than that, if one could but take away the great light of the crescent illuminated by the Sun, the presence of which much obscureth the other lesser.
Salv.Why, doth it not sometimes come to pass, that one may in a very dark night see the whole face of the Moon, without being at all illuminated by the Sun?
Simpl.I know not whether this ever happeneth, save onely in the total Ecclipses of the Moon.
Salv.Why, at that time this its light would appear very clear, being in a most obscure medium, and not darkned by the clarity of the luminous crescents: but in that position, how light did it appear to you?
Simpl.I have sometimes seen it of the colour of brass, and a little whitish; but at other times it hath been so obscure, that I have wholly lost the sight of it.
Salv.How then can that light be so natural, which you see so cleer in the close of the twilight, notwithstanding the impediment of the great and contiguous splendor of the crescents; and which again, in the more obscure time of night, all other light removed, appears not at all?
Simpl.I have heard of some that believed that same light to be participated to these crescents from the other Stars, and in particular from Venus, the Moons neighbour.
Salv.And this likewise is a vanity; because in the time of its total obscuration, it ought to appear more shining than ever; for you cannot say, that the shadow of the Earth intercepts the sight of Venus, or the other Stars. But to say true, it is not at that instant wholly deprived thereof, for that the Terrestrial Hemisphere, which in that time looketh towards the Moon, is that where it is night, that is, an intire privation of the light of the Sun. And if you but diligently observe, you will very sensibly perceive, that like as the Moon, when it is sharp-horned, doth give very little light to the Earth; and according as in her the parts illuminated by the Suns light do encrease: so likewise the splendor to our seeming encreaseth, which from her is reflected towards us; thus the Moon, whilst it is sharp-forked, and that by being between the Sun and the Earth, it discovereth a very great part of the Terrestrial Hemisphere illuminated, appeareth very clear: and departing from the Sun, and passing towards the * By the Moons two Quadratures you are to understand its first and last quarters, as Astrologers call them*Quadrature, you may see the said light by degrees to grow dim; and after the Quadrature, the same appears very weak, because it continually loseth more and more of the view of the luminous part of the Earth: and yet it should succeed quite contrary, if that light were its own, or communicated to it from the Stars; for then we should see it in the depth of night, and in so very dark an ambient.
Simpl.Stay a little; for I just now remember, that I have read in a little modern tract, full of many novelties; "That this secondary light is not derived from the Stars, nor innate in the Moon, and least of all communicated by the Earth, but that it is received from the same illumination of the Sun,The secondary light of the Moon caused by the Sun, according to some. which, the substance of the Lunar Globe being somewhat transparent, penetrateth thorow all its body; but more livelily illuminateth the superficies of the Hemisphere exposed to the rays of the Sun: and its profundity imbuing, and (as I may say) swallowing that light, after the manner of a cloud or chrystal, transmits it, and renders it visibly lucid. And this (if I remember aright) he proveth by Authority, Experience and Reason; citing Cleomedes, Vitellion, Macrobius, and a certain other modern Author: and adding, That it is seen by experience to shine most in the days nearest the Conjunction, that is, when it is horned, and is chiefly bright about its limb. And he farther writes, That in the Solar Ecclipses, when it is under the Discus of the Sun, it may be seen translucid, and more especially towards its utmost Circle. And in the next place, for Arguments, as I think, he saith, That it not being able to derive that light either from the Earth, or from the Stars, or from it self, it necessarily follows, that it cometh from the Sun. Besides that, if you do but grant this supposition, one may easily give convenient reasons for all the particulars that occur. For the reason why that secundary light shews more lively towards the outmost limb, is, the shortness of the space that the Suns rays hath to penetrate, in regard that of the lines which pass through a circle, the greatest is that which passeth through the centre, and of the rest, those which are farthest from it, are always less than those that are nearer. From the same principle, he saith, may be shewn why the said light doth not much diminish. And lastly, by this way the cause is assigned whence it comes, that that same more shining circle about the utmost edge of the Moon, is seen at the time of the Solar Ecclipse, in that part which lyeth just under the Discus of the Sun, but not in that which is beside the Discus: which happeneth because the rays of the Sun pass directly to our eye, through the parts of the Moon underneath: but as for the parts which are besides it, they fall besides the eye."
Salv.If this Philosopher had been the first Author of this opinion, I would not wonder that he should be so affectionate to it, as to have received it for truth; but borrowing it from others, I cannot find any reason sufficient to excuse him for not perceiving its fallacies; and especially after he had heard the true cause of that effect, and had it in his power to satisfie himself by a thousand experiments, and manifest circumstances, that the same proceeded from the reflection of the Earth, and from nothing else: and the more this speculation makes something to be desired, in the judgment of this Author, and of all those who give no credit to it: so much the more doth their not having understood and remembred it, excuse those more recess Antients, who, I am very certain, did they now understand it, would without the least repugnance admit thereof. And if I may freely tell you what I think, I cannot believe but that this Modern doth in his heart believe it; but I rather think, that the conceit he should not be the first Author thereof, did a little move him to endeavour to suppresse it, or to disparage it at least amongst the simple, whose number we know to be very great; and many there are, who much more affect the numerous applauds of the people, than the approbation of a few not vulgar judgments.
Sagr.Hold good Salviatus, for me thinks, I see that you go not the way to hit the true mark in this your discourse, for these that* Tendono le parete al commune. * confound all propriety, know also how to make themselves Authors of others Inventions, provided they be not so stale, and publick in the Schools and Market-places, as that they are more then notorious to every one.
Salv.Ha! well aimed, you blame me for roving from the point in hand; but what have you to do with Schools and Markets? Its all one whether opinions be new to men, or men new to opinions. Is it not all one whether opinions and inventions be new to men, or the men new to them? If you* Contestare falsly rendered in the Latine Translation contentare. *contend about the esteem of the Founders of Sciences, which in all times do start up, you may make your self their inventor, even to the Alphabet it self, and so gain admiration amongst that illiterate rabble; and though in processe of time your craft should be perceived, that would but little prejudice your designe; for that others would succeed them in maintaining the number of your fautors; but let us return to prove to Simplicius the invalidity of the reasons of his modern Author, in which there are several falsities, inconsequencies,The secondary light of the Moon appears in form of a Ring, that is to say, bright in the extreme circumference, and not in the midst, and why. and incredible Paradoxes. And first, it is false that this secondary light is clearer about the utmost limb than in the middle parts, so as to form, as it were, a ring or circle more bright than the rest of its space or contence. True it is, indeed, that looking on the Moon at the time of twilight, at first sight there is the resemblance of such a circle, but by an illusion arising from the diversity of confines that bound the Moons Discus, which are confused by means of this secondary light; forasmuch as on the part towards the Sun it is bounded by the lucid horns of the Moon, and on the other part, its confining term is the obscure tract of the twilight; whose relation makes us think the candor of the Moons Discus to be so much the clearer; the which happens to be obfuscated in the opposite part, by the greater clarity of the crescents; but if this modern Author had essaied to make an interposition between the eye and the primary splendor,The way to observe the secondary light of the Moon. by the ridg of some house, or some other screen, so as to have left visible only the grose of the Moon, the horns excluded, he might have seen it all alike luminous.
Simpl, I think, now I remember, that he writes of his making use of such another Artifice, to hide from us the false lucidum.
Salv.Oh! how is this (as I believed) inadvertency of his, changed into a lie, bordering on rashnesse; for that every one may frequently make proof of the contrary. That in the next place,The Moons Discus in a solar Eclipse can be seen onely by privation. at the Suns Eclipse, the Moons Discus is seen otherwayes than by privation, I much doubt, and specially when the Eclipse is not total, as those must necessarily have been, which were observed by the Author; but if also he should have discovered somewhat of light, this contradicts not, rather favoureth our opinion; for that at such a time, the whole Terrestrial Hemisphere illuminated by the Sun, is opposite to the Moon, so that although the Moons shadow doth obscure a part thereof, yet this is very small in comparison of that which remains illuminated. That which he farther adds, that in this case, the part of the limb, lying under the Sun, doth appear very lucid, but that which lyeth besides it, not so; and that to proceed from the coming of the solar rayes directly through that part to the eye, but not through this, is really one of those fopperies, which discover the other fictions, of him which relates them: For if it be requisite to the making a secondary light visible in the lunar Discus, that the rayes of the Sun came directly through it to our eyes, doth not this pitiful Philosopher perceive, that we should never see this same secondary light, save onely at the Eclipse of the Sun? And if a part onely of the Moon, far lesse than half a degree, by being remote from the Suns Discus, can deflect or deviate the rayes of the Sun, so that they arrive not at our eye; what shall it do when it is distant twenty or thirty degrees, as it is at its first apparition? and what course shall the rayes of the Sun keep, which are to passe thorow the body of the Moon, that they may find out our eye?The Author of the Book of conclusions, accommodates the things to his purposes, and not his purposes to the things. This man doth go successively considering what things ought to be, that they may serve his purpose, but doth not gradually proceed, accommodating his conceits to the things, as really they are. As for instance, to make the light of the Sun capable to penetrate the substance of the Moon, he makes her in part diaphanous, as is v. g. the transparence of a cloud, or crystal: but I know not what he would think of such a transparency, in case the solar rayes were to passe a depth of clouds of above two thousand miles; but let it be supposed that he should boldly answer, that might well be in the Cœlestial, which are quite other things from these our Elementary, impure, and feculent bodies; and let us convict his error by such wayes, as admit him no reply, or (to say better) subter-fuge. If he will maintain, that the substance of the Moon is diaphanous, he must say that it is so, whilest that the rayes of the Sun are to penetrate its whole profundity, that is, more than two thousand miles; but that if you oppose unto them onely one mile, or lesse, they should no more penetrate that, than they penetrate one of our mountains.
Sagr.You put me in mind of a man,A jest put upon one that would sell a certain secret for holding correspondency with a person a thousand miles off. who would have sold me a secret how to correspond, by means of a certain sympathy of magnetick needles, with one, that should be two or three thousand miles distant; and I telling him, that I would willingly buy the same, but that I desired first to see the experiment thereof, and that it did suffice me to make it, I being in one Chamber, and he in the next, he answered me, that in so small a distance one could not so well perceive the operation; whereupon I turn'd him going, telling him, that I had no mind, at that time, to take a journey unto Grand Cairo, or to Muscovy, to make the experiment; but that, if he would go himself, I would perform the other part, staying in Venice. But let us hear whither the deduction of our Author tendeth, and what necessity there is, that he must grant the matter of the Moon to be most perforable by the rayes of the Sun, in a depth of two thousand miles, but more opacous than one of our mountains, in a thicknesse of one mile onely.
Salv.The very mountains of the Moon themselves are a proof thereof, which percussed on one side of the Sun, do cast on the contrary side very dark shadows, terminate, and more distinct by much, than the shadows of ours; but had these mountains been diaphanous, we could never have come to the knowledg of any unevennesse in the superficies of the Moon, not have seen those luminous montuosities distinguished by the terms which separate the lucid parts from the dark: much lesse, should we see this same term so distinct, if it were true, that the Suns light did penetrate the whole thicknesse of the Moon; yea rather, according to the Authors own words, we should of necessity discern the passage, and confine, between the part of the Sun seen, and the part not seen, to be very confused, and mixt with light and darknesse; for that that matter which admits the passage of the Suns rayes thorow a space of two thousand miles, must needs be so transparent, that it would very weakly resist them in a hundredth, or lesser part of that thicknesse; neverthelesse, the term which separateth the part illuminated from the obscure, is incident, and as distinct, as white is distinct from black; and especially where the Section passeth through the part of the Moon, that is naturally more clear and montanous; but where the old spots do part, which are certain plains, that by means of their spherical inclination, receive the rayes of the Sun obliquely, there the term is not so distinct, by reason of the more dimme illumination. That, lastly, which he saith, how that the secondary light doth not diminish and languish, according as the Moon encreaseth, but conserveth it self continually in the same efficacy; is most false; nay it is hardly seen in the quadrature, when, on the contrary, it should appear more splendid, and be visible after the crepusculum in the dark of night. Let us conclude therefore, that the Earths reflection is very strong upon the Moon; and that, which you ought more to esteem, we may deduce from thence another admirable congruity between the Moon and Earth; namely, The Earth may reciprocally operate upon Cœlestial bodies, with its light. that if it be true, the Planets operate upon the Earth by their motion and light, the Earth may probably be no lesse potent in operating reciprocally upon them with the same light, and peradventure, motion also. And though it should not move, yet may it retain the same operation; because, as it hath been proved already, the action of the light is the self same, I mean of the light of the Sun reflected; and motion doth nothing, save only vary the aspects, which fall out in the same manner, whether we make the Earth move, and the Sun stand still, or the contrary.
Simpl.None of the Philosophers are found to have said, that these inferiour bodies operate on the Cœlestial, nay, Aristotle affirmes the direct contrary.
Salv.Aristotle and the rest, who knew not that the Earth and Moon mutually illuminated each other, are to be excused; but they would justly deserve our censure, if whilest they desire that we should grant and believe with them, that the Moon operateth upon the Earth with light, they should deny to us, who have taught them that the Earth illuminates the Moon, the operation the Earth hath on the Moon.
Simpl.In short, I find in my self a great unwillingnesse to admit this commerce, which you would perswade me to be betwixt the Earth and Moon, placing it, as we say, amongst the number of the Stars; for if there were nothing else, the great separation and distance between it and the Cœlestial bodies, doth in my opinion necessarily conclude a vast disparity between them.
Salv.See Simplicius what an inveterate affection and radicated opinion can do, since it is so powerful, that it makes you think that those very things favour you, which you produce against your self. For if separation and distance are accidents sufficient to perswade with you a great diversity of natures, it must follow that proximity and contiguity import similitude.Affinity between he Earth & Moon in respect of their vicinity. Now how much more neerer is the Moon to the Earth, than to any other of the Cœlestial Orbs? You must acknowledg therefore, according to your own concession (and you shall have other Philosophers bear you company) that there is a very great affinity betwixt the Earth and Moon. Now let us proceed, and see whether any thing remains to be considered, touching those objections which you made against the resemblances that are between these two bodies.
Simpl.It rests, that we say something touching the solidity of the Moon, which I argued from its being exquisite smooth and polite, and you from its montuosity. There is another scruple also comes into my mind, from an opinion which I have, that the Seas reflection ought by the equality of its surface, to be rendered stronger than that of the Earth, whose superficies is so rough and opacous.
Salv.As to the first objection; I say, that like as among the parts of the Earth,Solidity of the Lunar Globe argued from its being montainous. which all by their gravity strive to approach the nearest they can possible to the center, some of them alwayes are more remote from it than the rest, as the mountains more than the valleys, and that by reason of their solidity and firmnesse (for if they were of fluid, they would be even) so the seeing some parts of the Moon to be elevated above the sphericity of the lower parts, argueth their hardnesse; for it is probable that the matter of the Moon is reduced into a spherical form by the harmonious conspiration of all its parts to the same sentense. Touching the second doubt, my thinks that the particulars already observed to happen in the Looking-glasses, may very well assure us, that the reflection of light comming from the Sea,The Seas reflection of light much weaker than that of the Earth. is far weaker than that which cometh from Land; understanding it alwayes of the universal reflection; for as to that particular, on which the water being calm, casteth upon a determinate place, there is no doubt, but that he who shall stand in that place, shall see a very great reflection in the water, but every way else he shall see the surface of the Water more obscure than that of the Land;An experiment to prove the reflection of the Water lesse clear than that of the Land. and to prove it to your senses, let us go into yonder Hall, and power forth a little water upon the Pavement. Tell me now, doth not this wet brick shew more dull than the other dry ones? Doubtlesse it doth, and will so appear, from what place soever you behold it, except one onely, and this is that way which the light cometh, that entereth in at yonder window; go backwards therefore by a little and a little.
Simpl.Here I see the west part shine more than all the rest of the pavement, and I see that it so hapneth, because the reflection of the light which entereth in at the window, cometh towards me.
Salv.That moisture hath done no more but filled those little cavities which are in the brick with water, and reduced its superficies to an exact evenesse; whereupon the reflex rayes issue unitedly towards one and the same place; but the rest of the pavement which is dry, hath its protuberances, that is, an innumerable variety of inclinations in its smallest particles; whereupon the reflections of the light scatter towards all parts, but more weakly than if they had gone all united together; and therefore, the same sheweth almost all alike, beheld several wayes, but far lesse clear than the moistned brick. I conclude therefore, that the surface of the Sea, beheld from the Moon, in like manner, as it would appear most equal, (the Islands and Rocks deducted) so it would shew lesse clear than that of the Earth, which is montanous and uneven. And but that I would not seem, as the saying is, to harp too much on one string, I could tell you that I have observed in the Moon that secondary light which I told you came to her from the reflection of the Terrestrial Globe, to be notably more clear two or three dayes before the conjunction,The secondary light of the Moon clearer before the conjunction, than after. than after, that is, when we see it before break of day in the East, than when it is seen at night after Sun-set in the West; of which difference the cause is, that the Terrestrial Hemisphere, which looks towards the Eastern Moon, hath little Sea, and much Land, to wit, all Asia, whereas, when it is in the West, it beholds very great Seas, that is, the whole Atlantick Ocean as far as America: An Argument sufficiently probable that the surface of the water appears lesse splendid than that of the Earth.
Simpl.So that perhaps you believe, those great spots discovered in the face of the Moon, to be Seas, and the other clearer parts to be Land, or some such thing?
Salv.This which you ask me, is the beginning of those incongruities which I esteem to be between the Moon and the Earth, out of which it is time to dis-ingage our selves, for we have stayed too long in the Moon. I say therefore, that if there were in nature but one way onely, to make two superficies illustrated by the Sun, to appear one more clear than the other, and that this were by the being of the one Earth, and the other Water; it would be necessary to say that the surface of the Moon were part earthy and part aquatick; but because we know many wayes to produce the same effect (and others there may be which we know not of;) therefore I dare not affirm the Moon to consist of one thing more than another: It hath been seen already that a silver plate boiled, being toucht with the Burnisher, becometh of white obscure; that the moist part of the Earth shews more obscure than the dry; that in the tops of Hills, the woody parts appear more gloomy than the naked and barren; which hapneth because there falleth very much shadow among the Trees, but the open places are illuminated all over by the Sun. And this mixtion of shadow hath such operation, that in tufted velvet, the silk which is cut, is of a far darker colour than that which is not cut, by means of the shadows diffused betwixt thred and thred, and a plain velvet shews much blacker than a Taffata, made of the same silk. So that if there were in the Moon things which should look like great Woods, their aspect might represent unto us the spots which we discover; alike difference would be occasioned, if there were Seas in her: and lastly, nothing hindreth, but that those spots may really be of an obscurer colour than the rest; for thus the snow makes the mountains shew brighter.The obscurer parts of the Moon are plains, and the more bright mountainous. That which is plainly observed in the Moon is, that its most obscure parts are all plains, with few rises and bancks in them; though some there be; the rest which is of a brighter colour, is all full of rocks, mountains, hillocks of spherical and other figures; and in particular, round about the spots are very great ledges of mountains.Long ledges of mountains about the spots of the Moon. That the spots be plain superficies, we have assured proof, in that we see, how that the term which distinguisheth the part illuminated from the obscure, in crossing the spots makes the intersection even, but in the clear parts it shews all craggy and shagged. But I know not as yet whether this evennesse of superficies may be sufficient of it self alone, to make the obscurity appear, and I rather think not. Besides, I account the Moon exceeding different from the Earth; for although I imagine to my self that those are not idle and dead Regions,There are not generated in the Moon things like to ours, but if there be any productions, they are very different. yet I affirm not, that there are in them motion and life, much less that there are bred plants, animals or other things like to ours; but, if such there be, they should nevertheless be very different, and remote from our imagination. And I am induced so to think, because in the first place, I esteem that the matter of the Lunar Globe consists not of Earth and Water; and this alone sufficeth to take away the generations and alterations resembling ours:The Moon not composed of Water and Earth. but now supposing that there were in the Moon, Water and Earth, yet would they not produce plants and animals like to ours;Those aspects of the Sun necessary for our generations, are not so in the Moon. and this for two principal reasons: The first is, that unto our productions there are required so many variable aspects of the Sun, that without them they would all miscarry: now the habitudes of the Sun towards the Earth are far different from those towards the Moon. We as to the diurnal illumination, have, in the greater part of the Earth, every twenty four hours part day, and part night, which effect in the Moon is monethly: and that annual declination and elevation of the Sun in the Zodiack,Natural dayes in the Moon are of a Moneth long. by which it produceth diversity of Seasons, and inequality of dayes and nights, are finished in the Moon in a moneth; and whereas the Sun to us riseth and declineth so much,To the Moon the Sun ascendeth and declineth with a difference of ten degrees, and to the Earth of forty seven degrees. that from the greatest to the least altitude, there is a difference of almost 47 degrees, for so much is the distance from one to the other Tropick; this is in the Moon but ten degrees only, or little more; namely, as much as the greatest Latitudes of the Dragon on each side the Ecliptick. Now consider what effect the Sun would have in the torrid Zone, should it continually for fifteen dayes together beam forth its Rayes upon it; which without all question would destroy plants, herbs, and living creatures: and if it should chance that there were any production, it would be of herbs, plants, and creatures very different from those which are now there.There are no rains in the Moon. Secondly, I verily believe that in the Moon there are no rains, for if Clouds should gather in any part thereof, as they do about the Earth, they would thereupon hide from our sight some of those things, which we with the Telescope behold in the Moon, and in a word, would some way or other change its Phænomenon, an effect which I could never by long and diligent observations discover; but alwayes beheld it in a even and pure serenity.
Sagr.To this may be answered, either that there might be great mists, or that it might rain in the time of their night, that is, when the Sun doth not illuminate it.
Salv.If other passages did but assure us, that there were generations in it like to ours, and that there was onely wanting the concourse of rains, we might find out this, or some other temperament to serve instead thereof, as it happens in Egypt by the inundation of Nile: but not meeting with any accident, which corresponds with ours, of many that have been sought out for the production of the like effects, we need not trouble our selves to introduce one alone; and that also, not because we have certain observation of it, but for a bare non-repugnance that we find therein. Moreover, if I was demanded what my first apprehension, and pure natural reason dictated to me concerning the production of things like or unlike there above, I would alwayes reply, that they are most different, and to us altogether unimaginable, for so me thinks the riches of Nature, and the omnipotence of our Creator and Governour, do require.
Sagr.I ever accounted extraordinary madnesse that of those, who would make humane comprehension the measure of what nature hath a power or knowledge to effect; whereas on the contrary there is not any the least effect in Nature,The having a perfect knowledg of nothing, maketh some believe they understand all things. which can be fully understood by the most speculative wits in the world. This their so vain presumption of knowing all, can take beginning from nothing, unlesse from their never having known any thing; for if one hath but once onely experienced the perfect knowledg of one onely thing, and but truly tasted what it is to know, he shall perceive that of infinite other conclusions, he understands not so much as one.
Salv.Your discourse is very concluding; in confirmation of which we have the example of those who understand, or have known some thing, which the more knowing they are, the more they know, and freely confesse that they know little; nay, the wisest man in all Greece, and for such pronounced by the Oracle, openly professed to know that he knew nothing.
Simpl.It must be granted therefore, either that Socrates or that the Oracle it self was a lyar, that declaring him to be most wise, and he confessing that he knew himself to be most ignorant.
Salv.Neither one nor the other doth follow,The answer of the Oracle true in judging Socrates the wisest of his time. for that both the assertions may be true. The Oracle adjudged Socrates the wisest of all men, whose knowledg is limited; Socrates acknowledgeth that he knew nothing in relation to absolute wisdome, which is infinite; and because of infinite, much is the same part, as is little, and as is nothing (for to arrive v. g. to the infinite number, it is all one to accumulate thousands, tens, or ciphers,) therefore Socrates well perceived his wisdom to be nothing, in comparison of the infinite knowledg which he wanted. But yet, because there is some knowledg found amongst men, and this not equally shared to all, Socrates might have a greater share thereof than others, and therefore verified the answer of the Oracle.
Sagr.I think I very well understand this particular amongst men, Simplicius there is a power of operating, but not equally dispensed to all; and it is without question, that the power of an Emperor is far greater than that of a private person; but, both this and that are nothing in comparison of the Divine Omnipotence. Amongst men, there are some that better understand Agriculture than many others; but the knowledg of planting a Vine in a trench, what hath it to do with the knowledg of making it to sprout forth, to attract nourishment, to select this good part from that other, for to make thereof leaves, another to make sprouts, another to make grapes, another to make raisins, another to make the huskes of them, which are the works of most wise Nature? This is one only particular act of the innumerable, which Nature doth,Divine Wisdom infinitely infinite. and in it alone is discovered an infinite wisdom, so that Divine Wisdom may be concluded to be infinitely infinite.
Salv.Take hereof another example. Do we not say that the judicious discovering of a most lovely Statua in a piece of Marble, hath sublimated the wit of Buonarruotti far above the vulgar wits of other men?Buonarruotti, a statuary of admirable ingenuity. And yet this work is onely the imitation of a meer aptitude and disposition of exteriour and superficial members of an immoveable man; but what is it in comparison of a man made by nature, composed of as many exteriour and interiour members, of so many muscles, tendons, nerves, bones, which serve to so many and sundry motions? but what shall we say of the senses, and of the powers of the soul, and lastly, of the understanding? May we not say, and that with reason, that the structure of a Statue fals far short of the formation of a living man, yea more of a contemptible worm?
Sagr.And what difference think you, was there betwixt the Dove of Architas, and one made by Nature?
Simpl.Either I am none of these knowing men, or else there is a manifest contradiction in this your discourse. You account understanding amongst the greatest (if you make it not the chief of the) Encomiums ascribed to man made by Nature, and a little before you said with Socrates, that he had no knowledg at all; therefore you must say, that neither did Nature understand how to make an understanding that understandeth.
Salv.You argue very cunningly, but to reply to your objection I must have recourse to a Philosophical distinction, and say that the understanding is to be taken too ways,Man understandeth very well intensivè, but little extensivè that is intensivè, or extensivè; and that extensivè, that is, as to the multitude of intelligibles, which are infinite, the understanding of man is as nothing, though he should understand a thousand propositions; for that a thousand, in respect of infinity is but as a cypher: but taking the understanding intensive, (in as much as that term imports) intensively, that is, perfectly some propositions, I say, that humane wisdom understandeth some propositions so perfectly, and is as absolutely certain thereof, as Nature her self; and such are the pure Mathematical sciences, to wit, Geometry and Arithmetick: in which Divine Wisdom knows infinite more propositions, because it knows them all; but I believe that the knowledge of those few comprehended by humane understanding, equalleth the divine, as to the certainty objectivè, for that it arriveth to comprehend the necessity thereof, than which there can be no greater certainty.
Simpl.This seemeth to me a very bold and rash expression.
Salv.These are common notions, and far from all umbrage of temerity, or boldness, and detract not in the least from the Majesty of divine wisdom; as it nothing diminisheth the omnipotence thereof to say, that God cannot make what is once done, to be undone: but I doubt, Simplicius, that your scruple ariseth from an opinion you have, that my words are somewhat equivocal; therefore the better to express my self I say, that as to the truth, of which Mathematical demonstrations give us the knowledge, it is the same, which the divine wisdom knoweth; but this I must grant you,Gods manner of knowing different from that of men. that the manner whereby God knoweth the infinite propositions, of which we understand some few, is highly more excellent than ours,Humane understanding done by raciocination. which proceedeth by ratiocination, and passeth from conclusion to conclusion, whereas his is done at one single thought or intuition; and whereas we, for example, to attain the knowledg of some passion of the Circle, which hath infinite, beginning from one of the most simple, and taking that for its definition, do proceed with argumentation to another, and from that to a third, and then to a fourth, &c. the Divine Wisdom, by the apprehension of its essence comprehends, without temporary raciocination, all these infinite passions; which notwithstanding, are in effect virtually comprised in the definitions of all things;Definitions contein virtually all the passions of the things defined. and, to conclude, as being infinite, perhaps are but one alone in their nature, and in the Divine Mind; the which neither is wholly unknown to humane understanding,Infinite Passions are perhaps but one onely. but onely be-clouded with thick and grosse mists; which come in part to be dissipated and clarified, when we are made Masters of any conclusions, firmly demonstrated, and so perfectly made ours, as that we can speedily run through them; for in sum, what other, is that proposition, that the square of the side subtending the right angle in any triangle, is equal to the squares of the other two, which include it, but onely the Paralellograms being upon common bases, and between parallels equal amongst themselves? and this, lastly, is it not the same, as to say that those two superficies are equal, of which equal parts applyed to equal parts,The discourses which humane reason makes in a certain time, the Divine Wisdom resolveth in a moment; that is, hath them alwayes present. possesse equal place? Now these inferences, which our intellect apprehendeth with time and a gradual motion, the Divine Wisdom, like light, penetrateth in an instant, which is the same as to say, hath them alwayes present: I conclude therefore, that our understanding, both as to the manner and the multitude of the things comprehended by us, is infinitely surpast by the Divine Wisdom; but yet I do not so vilifie it, as to repute it absolutely nothing; yea rather, when I consider how many and how great misteries men have understood, discovered, and contrived, I very plainly know and understand the mind of man to be one of the works, yea one of the most excellent works of God.
Sagr.I have oft times considered with my self,The wit of man admirably acute. in pursuance of that which you speak of, how great the wit of man is; and whil'st I run thorow such and so many admirable inventions found out by him, as well in the Arts, as Sciences; and again reflecting upon my own wit, so far from promising me the discovery of any thing new, that I despair of comprehending what is already discovered, confounded with wonder, and surprised with desperation, I account my self little lesse than miserable. If I behold a Statue of some excellent Master, I say with my self; When wilt thou know how to chizzle away the refuse of a piece of Marble, and discover so lovely a figure, as lyeth hid therein? When wilt thou mix and spread so many different colours upon a Cloth, or Wall, and represent therewith all visible objects, like a Michael Angelo, a Raphaello, or a Tizvano? If I behold what inventions men have in comparting Musical intervals, in establishing Precepts and Rules for the management thereof with admirable delight to the ear: When shall I cease my astonishment? What shall I say of such and so various Instruments of that Art? The reading of excellent Poets, with what admiration doth it swell any one that attentively considereth the invention of conceits, and their explanation? What shall we say of Architecture? What of Navigation?The invention of writing stupendious above all others. But, above all other stupendious inventions, what sublimity of mind was that in him, that imagined to himself to find out a way to communicate his most secret thoughts to any other person, though very far distant from him either in time, or place, speaking with those that are in the India's; speaking to those that are not yet born, nor shall be this thousand, or ten thousand years? and with how much facility? but by the various collocation of* For of so many only the Italian Alphabet consists. * twenty little letters upon a paper? Let this be the Seal of all the admirable inventions of man, and the close of our Discourse for this day: For the warmer hours being past, I suppose that Salviatus hath a desire to go and take the air in his Gondelo; but too morrow we will both wait upon you, to continue the Discourses we have begun, &c.