Philosophical Transactions/Volume 1/Number 17

Num. 17.



Munday, Septemb. 9. 1666.

The Contents.

Observations made in several places (at London, Madrid and Paris,) of the late Eclipse of the Sun, which hapned June 22. 1666.Some Enquiries and Directions, concerning Tides, proposed by Dr. Wallis.Considerations and Enquiries touching the same Argument, suggested by Sir Robert Moray.An Account of several Books lately publish't: Vid.1. Johannis Hevelii Descriptio Cometæ, A. 1665. exorti; una cum Mantissa Prodromi Cometici.2. Isaacus Vossius de Nili & aliorum Fluminum Origine.3. Le Discernement du Corps & de l'Ame, par Monsieur de Cordemoy.

Observations made in several places, Of the late Eclipse of the Sun, which hapned on the 22 of June, 1666.

THe Observations that were made at London by Mr. Willughby, Dr. Pope, Mr. Hook, and Mr. Philips, are these:

   The Eclipse began at 5h. 43′ h
It was
diam. at 6. 00     5 dig. at 7. 06
4 dig. at 6. 07 4 dig. at 7. 13
5 dig. at 6. 13 3 dig. at 7. 20
6 dig. at 6. 21 2 dig. at 7. 26
7 dig. at 6. 39½ 1 dig. at 7. 32
6 dig. at 6. 57 0 dig. at 7. 37

Its Duration hence appears to have been one hour and 54 m. Its greatest Obscurity somewhat more than 7. digits. About the middle, between the Perpendicular and Westward Horizontal Radius of the Sun, viewing it through Mr Boyle's 60. foot Telescope, there was perceived a little of the Limb of the Moon without the Diske of the Sun: which seemed to some of the Observers to come from some shining Atmosphere about the Body either of the Sun or Moon.

They affirm to have observ'd the Figure of this Eclipse, and measured the Digits, by casting the Figure through a 5 foot Telescope, on an extended paper, fix't at a certain distance from the Eye-glasse, and having a round figure; all whose Diameters were divided, by 6 Concentrick Circles, into 12 Digits.

THe Observations made at Madrid by a Noble Member of the Royal Society, His Excellence the Earle of Sandwich, as they were sent to the Right Honourable, the Lord Vice Count Brounker, are these;

The Eclipse began at Madrid about 5 of the Clock in the morning, at 35′. the Suns Altitude was 6 deg. 55′.

The Middle of it was at 6 h. 2′; the Suns Altitude, 15. deg. 5′.

The End was exactly at 7 h. 5′; the Suns Altitude, 25. deg. 24′.

The Duration, 2 h. 4′.

37. Parts of the Suns diameter remained light.

63. Parts of the same were darkened.

The Observations made at Paris by Monsieur Payen, assisted by several Astronomers, as they were printed in French, and addressed to Monsieur de Montmar are these;

The Ecplise began there, at 5 h. 44′. 52″. mane. It ended at 7 h. 43′. 6″. So that is Whole duration was 1h 58′. 14″. The greatest Obscuration they assign to have been 7. dig. 50. m. but they adde, that it seem'd to have been greater by 3 minuts, which M. Payen imputes to a particular motion of Libration of the Suns Globe, which entertain'd that Luminary in the same Phasis for the space of 8. min. and some seconds, as if it had been stopped in the midst of its Course; rather than to a tremulous Motion of the Atmosphere, as Scheiner would have it.

They intimate that they took the time of each Phasis from half digit to half digit, as well by a Pendulum, as by the Attitudes of the Suns Center above the Horizon, corrected by the Verticall Paralaxes of the Æstivall Refractions, by which they judged, that though the Time by the Pendulum, may be sufficient for Mechanicall Operations, yet 'tis not exact enough for establishing the Grounds of true Astonomy.

They further conceive that the apparent Diameters were almost equal; seeing that in the Phasis of 6. Digits, the Cirucumference of the Moons disk passed through the Center of that of the Sun, so as that two Lines drawn through the two Horns of the Sun, made with the Common Semi-diameter two Equilateral Triangles.

Next, they affirm, That there was so great a Variation in the Parallaxes, by reason as well of the Refractions of the Air, which environs the Earth, as of the Alteration of the Air, which encompasses the Moon, that the Horns of the Sun, there formed by the Shaddow of the Moon, appeared in all kinds of Figures; Sometimes inclined to the Vertical, sometimes Perpendicular to the Horizon, and at last Parallel; the Convex part respecting the Heaven, and the Concave, the Horizon, By the crossing (so they go on) of the Horns with the Angles of Inclination, it will be easie to those, that have exactly observed them, and that are skill'd in the higher Astronomical Calculations, to compute the true Place of the Moon in her Orbite, that so it may be compared with that of the Tables, and with that, which has been observ'd in other places, for the more precise determinating of the Difference of Meridians (that being the way, esteem'd by Kepler the most certain) and for making a good judgment of the defect or exactnesse of the Celestial Tables.

Then they observe, That the Beginning and the Middle of this Eclipse hapned to be in the North Eastern Hemisphere, and the End, in the South-Eastern. The first Contact (as 'twere) of the two Disks was observ'd in the Superior Limb of the Suns Disk in, respect to the Vertical Line, and in the Inferior in respect to the Ecliptick: But the Middle, and the End were seen in the Superior Limb, in respect both to the Vertical and the Ecliptick: And (what to this Author seems extraordinary) both the Beginning and the End of this Eclipse hapned to be in the Oriental part of the Suns Disk.

Lastly, they take notice, that by their Observations it appears, that there is but little exactness in all the Astronomical Tables, predicting the Quantity, Beginning and Duration of this Eclipse; Those of Lansbergius importing, That the Obscuration should be of 10.dig.48′, those of Ricciolo, of 9 dig. 1′, and those of Kepler, of 7. dig. 30′. 16″: Again, that the Duration should be of 2h. 2′. Lastly, The Beginning did anticipate the Ricciolan Tables by 5. minuts; the End by 23; and the Middle, almost by 11. In the mean time the Author notes that the Rudolphin Tables come nearest to these Truth, and withal assures the Render of the goodnesse of the Instruments employed in his Observations, and of the singular care, he, together with his skilful Assistants, took in making them.

Some Inquiries and Directions concerning Tides, proposed by Dr. Wallis, for the proving or, disproving of his lately publish't Discourse concerning them.

The Inquisitive Dr. Wallis, having in his lately printed Hypothesis of Tides intimated, that he had reason to believe, that the Annual Spring-sides happen to be rather about the beginnings of Febr. and Nov. than the two, Æquinoxes, doth in a late Letter to the Publisher, written from Oxford in Aug. last, desire, Sea, some understanding Persons at London, or Greenwich, but rather nearer the that or upon the Sea-shore, would make particular Observation of all the Spring-Tides (New-Moon and Full-Moon) between this and the End of November; and take account of the Hoar, and of the Perpendicular height: that we may see, whether those in September, or those of November be highest: And it were not amiss, the Low waters were observed too. Which may be easily done by a mark made upon any standing Post in the Water, by any Water-man, or other understanding Person, who dwells by the Waterside.

It would also deserve (thinks he) to be inquired into, whether, when the Tides be highest, the Ebbs be ever lowest, & contra: (which is generally affirmed, and almost put out of question) or rather (which sutes best with his Hypothesis) whether, when the Tides are highest, both in the Annual and Menstrual Periods, the Low waters be not also highest; and at Neap-Tides, the Ebbes also very low.

He adds, that he should expect, that the Spring-Tides now coming, and those at the beginning of September, should not be so high, as those at the middle of September; and then lower again at the beginning of October, and after that, higher at the middle of October, and higher yet about the beginning of November (at the usual times of Spring-tides after the New and Full.)

Considerations and Enquiries concerning Tides, by Sir Robert Moray; likewise for a further search into Dr. Wallis's newly publish't Hypothesis.

In regard that the High and Low waters are observed to increase, and decrease regularly at several seasons, according to the Moons age, so as, about the New and Full Moon, or within two or three daies after, in the Western parts of Europe, the Tides are at the highest, and about the Quarter-Moons, at the Lowest, (the former call'd Spring-tides, the other Neap-tides;) and that according to the height and excesses of the Tides the Ebbes in opposition are answerable to them, the heighest Tide having the lowest Ebbe, and the lowest Ebbe, the highest Tide; the Tides from the Quarter to the highest Spring-tide increasing in a certain proportion; and from the Spring-tide to the Quarter-tide decreasing in like proportion, as is supposed: And also the Ebbes rising and falling constantly after the same manner: It is wished, that it may be inquired, in what proportion these Increases and Decreases, Risings and Fallings happen to be in regard of one another?

And 'tis supposed, upon some Observations, made in fit places, by the above-mentioned Gentleman, though, (as himself acknowledges) not thoroughly and exactly performed, that the Increase of the Tides is made in the Proportion of Sines; the first Increase exceeding the lowest in a small proportion; the next in a greater; the third greater than that; and so on to the mid-most, whereof the excess is greatest, diminishing again from that, to the highest Spring-Tide; so as the proportions, before and after the Middle, do greatly answer one another, or seem to do so. And likewise, from the highest Spring-tide, to the Lowest Neap-tide, the Decreases seem to keep the like proportions; the Ebbes rising and falling in like manner and in like proportions. All which is supposed to fall out, when no Wind or other Accident causes an alteration.

And whereas 'tis observed, that upon the main Sea-shore the Current of the Ebbings and Flowings is sometimes swifter, and sometimes slacker, than at others, so as in the beginning of the Floud the Tide moves faster but in a small degree, increasing its swiftness constantly till towards the Middle of the Floud, and then decreasing in velocity again from the Middle till to the top of the High-water, it is supposed, that in Equal spaces of Time, the Increase and Decrease of velocity, and consequently the degrees of the Risings and Fallings of the same, in Equal spaces of time, are performed according to the Proportion of Sines.

But 'tis withall conceived, that the said Proportion cannot hold exactly and precisely, in regard of the Inequalities, that fallout in the Periods of the Tides, which are commonly observed and believed to follow certain Positions of the Moon in regard of the Equinox, which are known not to keep a precise and constant Course: so that, there not intervening equal portions of Time between one New Moon and another, the Moons return to the same Meridian, cannot be alwaies perform'd in the same Time, and consequently there must be at like Variation of the Tides in the Velocity, and in the Risings and Fallings of the Tides, as to equal spaces of time. And the Tides from New-moon to New-moon being not alwaies the same in number, as sometimes but 57, sometimes 58, and sometimes 59, (without any certain order of succession) is another evidence of the difficulty of reducing this to any great exactness. Yet, because 'tis worth while, to learn as much of it, as may be, the Proposer and many others do desire, That Observations be constantly made of all these Particulars for some Months, and, if it may be, years together. And because such Observations will be the more easily and exactly made, where the Tides rise highest, it is presumed, that a fit Apparatus being made for the purpose, they may be made about Bristol or Cheap-stow, best of any places in England, because the Tides are said thereabout to rise to ten or twelve fathoms; as upon the coast of Britanny in France, they do to thirteen and fourteen.

In order to which, this following Apparatus is proposed to be made use of. In some convenient place upon a Wall, Rock, or Bridge, &c. let there be an Observatory standing, as neer as may be to the brink of the Sea, or upon some wall; and if it cannot be well placed full where the Low water is, there may be a Channel cut from the Low water to the bottom of the Wall, Rock, &c: The Observatory is to be raised above the High-water 18. or 20. foot; and a Pump, of any reasonable dimension, placed perpendicularly by the Wall, reaching above the High water as high as conveniently may be. Upon the top of the Pump a Pulley is to be fastned, for letting down into the Pump a piece of floating wood, which, as the water comes in, may rise and fall with it, And because the rising and falling of the water amounts to 60. or 70. foot, the Counterpoise of the weight, that goes into the Pump, is to hang upon as many Pulleys, as may serve to make it rise & fall within the space, by which the height of the Pump exceeds the height of the Water. And because by this means the Counterpoise will rise and fall slower, and consequently by less proportions, than the weight it self, the first Pulley may have upon it a Wheele or two, to turn Indexes at any proportion required, so as to give the minute parts of the motion and degrees of risings and fallings. All which is to be observed by Pendulum-Watches, that have Minutes and Seconds, with Cheeks, according to Mr. Hugens's way.

And because if the Hole, by which the water is let into the Pump, be as large as the Bore of the Pump it self, the weight that is raised by the water, will rise and fall with an Undulation, according to the inequality of the Sea's Surface, 'twill therefore be fit, that the Hole, by which the water enters, be less than half as bigg as the Bore of the Pump; any inconvenience that may follow thereupon, as to the Periods and Stations of the Floud and Ebb, not being considerable.

And to the end, that it may appear the better, what are the particular Observations, desired to be made, near Bristol or Cheap-stow bridg, it was thought not amiss, to set them down distinctly by themselves.

1. The degrees of the Rising and Falling of the water every quarter of an hour (or as often as conveniently may be) from the Periods of the Tides and Ebbs; to be observed night and day, for 2 or 3 months.

2. The degrees of the velocity of the Motion of the Water every quarter of an hour for some whole Tides together; to be observed by a second Pendul-watch; and a logg fastened to a line of some 50 fathoms, wound about a wheel.

3. The exact measures of the Heights of every utmost High-water and Low-water, from one Spring-tide to another, for some Months or rather Years.

4. The exact Heights of Spring-tides and Spring-Ebbs for some Years together.

5. The Position of the Wind at every observation of the Tides; and the times of its Changes; and the degrees of its Strength.

6. The State of the Weather, as to Rain, Hail, Mist, Haziness, &c. and the times of its Changes.

7. At the times of observation of the Tides, the height of the Thermometer; the height of the Baroscope; the height of the Hygroscope; the Age of the Moon, and her Azimuths; and her place in all respects; And lastly the Sun's place; all these to minutes.

And it would be convenient, to keep Journal Tables, for all these Observations, each answering to its day of the Month.

For the Apparatus of all these observations, there will be particularly necessary.

A good Pendulum-watch.

A Vane shewing Azimuths to minute parts.

An Instrument to measure the strength of the Winde.

A large and good needle shewing Azimuths to degrees.

Thermometers, Barometer, Hygrosopcopes.

These Observations being thought very considerable as well as curious, 'tis hoped, that those who have convenience, will give encouragement and assistance for the making of them; and withall oblige the publick by imparting, what they shall have observed of this kind: The Publisher intending, that when ever such observations shall be communicated to him he will give notice of it to the publick, and take care of the improvement thereof to the best use and advantage, A Pattern of the Table, proposed to be made for observing the Tides, is intended to be published the next opportunity, God permitting.

An Account
Of several Books lately published

1. Johannis Hevelii DESCRIPTION COMETÆ, Anno Æra Christianæ MDCLXV, exorti unà cum MANTISSA Prodromi Cometici, Observationes omnes prioris COMETÆ MDCLIV, exiisque genuinum motum accuratè deductum, cum Notis & Animadversionibus, exhibens.

This Book (as the Title it self intimates) undertakes two things. First, To give an Account of the Second of the two late Comets, which appeared, when the other was scarce extinct; Concerning which, the Author doth, from the Observations made by himself with a Sextant of 6 foot, and divided into minutes and seconds, assign both its true place (as well in respect of the Ecliptick as the Æquator) and its proper motion: Adding a fair Delineation of its Course, together with the genuine Representations of its Head and Train, in each day of its apparition; and subjoining a General Description and Discourse of some of the more notable Phenomena thereof. It was first seen at Dantzick by the Watchmen, the 5th of April st. n. 1665. and then observed by the Author from April 6. about 11/2. of the Clock in the morning, till April 20. at 3. in the morning. During which time, it went with a reasonable velocity; making 46deg. in its Orb, according to the Order of the Signes moving from the Breast of Pegasus, towards the Head of Andromeda, and the Left Horn of Aries; having, as 'tis presumed, taken its rise from above Sagittary, and run through the Breast of Antinous under Aquila, and the Dolphin, to the said Pegasus; and so on, as is already expressed.

The Head of it is in the Book described of a Colour like that of Jupiter, all along much brighter than that of the former Comet, though of somewhat less magnitude; having in its middle onely one round, but very bright and big Kernel or Speck, resplendent like Gold, and encompassed with another more dilute and seemingly uniform matter: its Tail being at first, about 17 deg. and afterwards 20. and sometimes 25. deg. long, and divaricated towards the End.

Next, it is observed, that though this Star did afterwards slacken its pace, yet it retained the vividness of its Colour, both of the Head and Train; the Head especially, keeping at the time as well of the last observations, as of the first, the brightness of its single kernel, though the environing more dilute matter were then almost all lost; it being, according to the Author, more and more attenuated, and grown narrow, the nearer the Star approached to the Sun.

Thirdly, 'tis noted, that this Comet did very much digress from the Hypothesis, delivered by M. Auzout, in regard that, whereas according to that Hypothesis, this Star should not arrive to the Ecliptick till after the space of 3 months, it arrived there the 28 of April. And then, that its first Conjunction with the Sun hapned between the 19 and 20 of April, and the second, the last of April, not (as M. Auzout, would have it) the 15 of May. So that he concludes, that this Comet never came down to the Pleiads and the Eye of Taurus, as the Hypothesis of M. Auzout requires, but that from April 20. it did immediately take its course towards the Ecliptick, deflecting every day more and more from the Section of a Great Circle, to the Lucida of Aries, arriving at the Ecliptick the last of April, about the 8th or 10th deg. of Taurus; not in July about the 8th of Gemini, and the Eye of Taurus.

Fourthly, He intimates, that if this Comet had appeared some few weeks sooner, it would have confronted the former Comet, being yet in its vigour and of a conspicuous bigness, in the same place, where that was, viz. the Head of Aries.

Fifthly, He observes, that this Star in progress of time became Retrograde, whence it came to pass, that in the Months of June and July it did not appear again before the Rising of the Sun, though the Sun left it far behind; whereas, if it had proceeded toward the Eye of Taurus, it would have appeared again in the morning.

Sixthly, He maintains, that this Comet was not the same with the former; which he thinks may be demonstrated, onely by a due Delineation of both their Course upon the Globe; where he saith it to be evident, that the former could never come to the Head of Pegasus, as moving already in February in a streight Course about the Head of Aries: Besides, that the former went in the very beginning in a Retrograde motion, but this perpetually in a direct one: that, about the end, very slow, its Head lessning and growing dark; this swift enough, with its head conspicuous and bright. To which he adds, that the whole Course of the former was made under at quite different Angle of the Orbite and Ecliptick, and a different Motion of the Nodes from the latter: As also that their Faces differed very much from one another, the first exhibiting all along a matter, which as to its density and rarity, altered from day to day exceedingly, whereas the second retained (to the Authors admiration, who affirms, never to have observed the like) all the time he saw it, one and the same round, dense and bright Speck or Kernel.

All which he concludes 1. With an Intimation of his sense concerning two other Comets, pretended to have been lately seen, One at Rome, about the Girdle of Andromeda, in the Months of February and March, 1664. the other in Germany in Capricorne, about Saturne in the head of 5agittary, during the Months of September and October, 1665. 2ly, With an Advertisement of what he has done in that important Work for the Advancement of Astronomy, the due Restitution of the Fixt Stars, vid. That he has almost finish't it, himself alone, without trusting to any other mans labour, that was not directed by him.

The Second Part of this Book (the Mantissa to the Prodromus Cometicus) endeavours to justifie the Authors Observations touching the former Comet, excepted against by M. Auzout, in several particulars, as 1. That it had not pass'd to the First, but Second Star in Aries, and had mov'd in quite another Line, than He had described. 2. That its proper motion about the end of January and the beginning of February, 1665. had not been rightly assigned. 3. That the Bignesse of its Diameter had not been truly delivered; Nor 4. The Faces of its Head in due manner represented.

To all which the Author endeavors to answer: 1. By delivering all his Observations of that Comet, thereby to shew, what care and diligence he had used, particularly to make out, how great its Diurnal motion had been, in what proportion, and how far, it decreased, and where and in what degree it increased again: Which being, as he conceives, duly and exactly deduced, and demonstrated, he esteems it afterwards to be easie for every one, versed in these matters, certainly to collect and to judge, what way the Comet, after it became invisible to the naked Eye, and could be no longer observed with Sextants and Quadrants, had taken, and what Line it had described. 2, By subjecting all those Observations, with great diligence and labour, to a rigid Calculus, thereby to obtain, for every day, the Longitudes, Latitudes, Right Ascensions, Declinations, Proper motion, Angle of the Ecliptick and the Æquator, and the Nodes of that Comet; for the construction of an Ephemerides of its whole Motion. From all which he pretends to prove, that he has not erred in his Observation of February 18. nor been prepossest by any Hypothesis, nor deluded by any Fixt Star, as M. Auzout thinketh, but that near the First Star' of Aries there then appear'd a Phænomenon, most like to that Comet, that was seen some dayes before, if compared with the Observations made thereof Febr. 12, 13, 14. Though he will not hitherto positively determine, whether that Phænomenon, which appear'd to him February 18. was indeed that very Comet, which he saw with his naked Eye, and observed with his Geometrical Instruments, the said 12, 13, and 14. dayes of February; or whether it was another, and whether he had lost that Comet, which moved towards the Second Star in Aries: but leaves it to the Learned World, and particularly to the Royal Society, after they shall have well examined and considered all his Observations, and the Calculus raised therefrom, to judge of this, and the other particulars in controversie.

II. Isaacus Vossius de NILI et ALOIRUM FLUMINUM ORIGINE. It was Numb. 14. of these Transactions, that gave an account of the Cause of the Inundation of the Nile, as it was rendred by Monsieur de la Chambre: This is to give you another, not only of the Inundation, but also of the Origine of that, and of other Rivers, as it is delivered by Monsieur Isaac Vossius, who undertakes in this Book to shew;

1. That those Subterraneous Channels, through which several Philosophers teach, that the Sea discharges it self into the Rivers, are not only imaginary, but useless, in regard 'tis impossible for the water to rise from the Subterraneous places up to the Mountains, where commonly the Sources of Rivers are.

2. He explicates, why, if a Pipe be put into a Bason full of Water, the water is seen more raised in the Pipe, than in the Bason, and rises higher according as the Pipe is narrower, On the contrary, if the same Pipe be put into a Bason full of Quicksilver, the Quicksilver stayes lower in the Pipe, than in the Bason. The reason, which he renders hereof, is, That as the Water sticks easily to all it touches, it is sustain'd by the sides of the narrow Pipe wherein it is included: And indeed, if the Pipe be quite drawn out of the Water, the Water doth not all fall out, but so much of it remains, as the sides of the Pipe could sustaine: Whence it is, that the Water which is kept up by the Walls of the Tube, weighing no longer upon that which is in the Bason, is thrust upwards, and keeps it self raised above its Levell; but the Quicksilver not adhering so easily, as Water, to Bodies it touches, is not sustained by the sides of the Tube, and so mounts not above its Levell, but rather descends below it, because the Pipe, which is streight, hinders the endeavor that is in the Mercury to rise to its Level. He adds, that this Observation makes nothing for the Explication of the Origine of Rivers; because, though it be true, that the Water by this means rises above its Levell, yet it does never run out at the top of the Pipe. Having said this, he answers to the other Arguments, commonly alledged to maintain this Opinion.

3. He pretends, that all Rivers proceed from a Colluvies or Rendevous of Rain-waters, and that, as the Water, that falls upon Hills, gathers more easily together, than that which falls in Plaines, therefore it is, that Rivers ordinarily take their Source from Hills. Thence also comes it (saies he) that there are more Rivers, than Torrents, in the Temperate Zones; and, on the contrary, more Torrents, than Rivers, in the Torrid Zone: For, as in hot Climats the Mountains are far higher, the Water, that descends from them with impetuosity, runs away in a little while, and formes such Collections of Water, as soon dry up; but in cold Climats, the Waters do not run away but slowly, and are renew'd and recruited by Rain, before they are quite dryed up; because the Hills are there lower, and so the Bed of Rivers hath lesse declivity.

Having thus discoursed of Rivers in General, he treats of the Nile in particular: and there

1. Observes, That the Order of the Seasons of the Year is quite inverted under the Torrid Zone. For, whereas it should be then Summer, when the Sun is near, and Winter, when the Sun is farther off: Under the Torrid Zone 'tis never lesse hot, than when the Sun is nearest; nor more hot, than when the Sun is farthest off: So that to the people that live between the Æquinoctial and the Tropicks, Summer begins about Christmass, and their Winter, about St. Johns day. The reason whereof is, (saith he) that when the Sun is directly over their Heads, it raises abundance of vapors, and draws them so high, that they are presently converted into Water by the coldnesse of the Air; whence it comes to passe, that then it rains continually, which does refresh the Air; but when the Sun is farther off, there falls no more rain, and so the Heat becomes insupportable,

2. He proves by many recent Relations, that the Sources of the Nile are on this side of the Æquinoctial in Æthiopia of which he gives a very accurate Mappe, correcting many faults which Geographers are wont to commit in the Description of the Kingdom of the Abyssins, which they believe to be much greater than indeed it is.

3. This supposed, he easily gives an account, why the Nile yearly overflows about the end of June: For, as at that time there falls much rain in Æthiopia, it must needs be, that the Nile, whose source is in that Country, should then overflow, when those rains begin, and subside, when they cease.

There are besides, in this Book, two other Tracts, In the first, M. Vossius endeavours to maintain the Doctrine, he had deliver'd in his Book De Lumine, and to shew, that the Soul of Animals is nothing but Fire, that there are no invisible Atoms, nor so much as any Pores, even in the Skin of man. Here he treats also of Refractions, and alledges the Examples of several persons, who have then seen the Sun by the means of Refraction, when really He was under the Horizon.

In the second, He discourses of some points of the Mechanicks; and relates among other things, that the Arrows and battering Rams (Aries) of the Antients did as much execution, as our Muskets and Canons, and then, that the Vehemence of the percussion depends as much upon the Length of the percutient Body, as upon the velocity of the Motion; He adds, that the Length of a Canon ought not to exceed 13 foot, and than a greater length is not onely useless, but hinders also the effect of the Gun, not because the Bullet is thrown out of the Gun, before all the powder is fired (as some believe;) but because the Bullet is then beaten back into the Gun by the Air, re-entring into it with impetuosity, when the flame is extinct.


This French Treatise (but very lately come to the Publisher's hands) examines the different Operations of the Soul and Body, and the Secret of their Union, pretending to discover to every one, what he is, and what is transecting within him. It consists of six Discourses.

1 In the first, the Author examines the Notions, we have in general of Bodies and Matter; of Quantity, of Qualities; of Place; of Rest, of Motion; of Vacuity; of Forms: to shew what is to be understood by these Terms, which cause all the perplexity that is in the ordinary Physicks. He begins with taking notice, hitherto Philosophers have had no distinct notions of Bodies and Matter, from the want whereof he conceives, that almost all the Errors in Common Physiology have sprung. To rectify which, he defines Bodies to be * Extended Substances, * It sounds hard, To say, An extended substance is Indivisible.and Matter an Aggregate of Bodies. Whence he inferrs, that Bodies are Indivisible and Matter divisible; a Body being nothing but one and the same substance, whose different extremities are inseparable, because they are the extremities of one and the same Extension, and, in a word, of one and the same Substance: but Matter being nothing but an Association or Collection of Bodies, 'tis evident, (saith he) it must be divisible. This doctrine he so much insists upon, that he conceives, Nature cannot subsist, if a Body in the sence he takes it, be divisible; and that Motion and Rest cannot be explicated without it. As for Quantity, he makes that to be nothing but More or Less Bodies; not allowing, that each Body should be a Quantity, though it be a part of Quantity; no more than an Unite is a Number, though it make part of a Number; so that Quantity and Extension are two distinct things with him, the first belonging properly to Matter, the last to a Body. Touching Vacuity, he conceives, that the Bodies, which compose a mass, are not every where so near one another, as not to leave some interval in several places. Neither does he think it necessary, that those intervals should be fill'd up; nor unconceivable, that there should be no Body between two Bodies, which touch not one another. And when 'tis said, that those intervals cannot be conceived without Extension, and that consequently there are Bodies that replenish them, he frankly pronounces that not to be true; and affirms, that though it may be said, that between two Bodies, which touch not one another, other Bodies may be placed of so or so many feet, &c: yet ought it not to be inferred, that therefore they are there, but onely, that they are thus placed, that there may be put between them so many Bodies, as joyned together would compose an Extension of so many feet. So that one conceives onely, that Bodies may be placed there, but not that they are there: and as we can have an Idea of many Bodies, though none of them be in being; so we can conceive, that some Bodies may be put between others, where really there are none. And when 'tis alledged, that if all the Bodies, that fill a vessel full, were destroyed, the sides of the vessel would be closed together; He professes he understands not that ratiocination, nor can conceive, what one Body does to the subsistence of another, more than to sustain themselves mutually, when they are thrust by the neighbouring ones: and therefore sees not, why the sides of the vessel should close, if nothing did thrust them together; but understands clearly, that two Bodies may well subsist so far from one another, that one might place a great many Bodies between them, or none at all, and yet they neither approach to, nor recoil from one another.

2. In the Second, he examines the Changes, which he knows in Matter, and makes it his business to explicate all those that respect Quantity, Qualities and Forms, by Local Motion, esteeming their needs no others

3. In the third, he explains the Motion of Artificial Engins, and that of Natural ones, by one and the same Cause; endeavouring among other things to shew, that the Body of an Animal is moved after the same manner with a Watch. That cause of motion he makes the Materia subtilis; and the finer or subtiler that is, the better and fitter he conceives it to be to preserve Motion.

4. In the Fourth, he teaches, that though Experience seems to evince, that the Soul moves the Body, and that one Body moves an other; yet there is nothing, but God, that can produce any motion in the World, and all other Agents, which we believe to be the Cause of this or that Motion, are no more but the Occasion thereof. In doing this, he advances certain Axioms, and Conclusions, which are in short,

a. The Axioms: That no substance has that of it self, which it can loose, without ceasing to be, what it is: That every body may loose of its motion, till it have no more left, without ceasing to be a Body: That we cannot conceive but two sorts of substances, vid. a Spirit (or That which thinketh) and a Body, wherefore they must be considered as the Causes of all, that happens, and what cannot proceed from the one, must necessarily be adscribed to the other; That to Move, or to cause motion, is an Action: That an Action cannot be continued but by the Agent, who began it.

b. The Conclusions; That no Body hath Motion of it self: That the First Mover of Bodies is not a Body: That it cannot be but a Spirit, that is the First Mover; That it cannot be but the same Spirit, who has begun to move Bodies, that continues to move.

In the Fifth, He treats of the Union of the Body and Soul, and the manner, how they act one upon the other; and esteems it not more difficult to conceive the Action of Spirits upon Bodies, and of Bodies upon Spirits, than to conceive the Action of Bodies upon Bodies: the cause of the great difficulty in understanding the two former; arising (according to him) from thence, that we will conceive the one by the other, not considering, that every thing acting according to its own nature, we shall never know the action of one Agent, if we will examine it by the notions we have of another, that is of a quite differing nature. Here he notes, that the Action of Bodies upon Bodies is not more known to us, than that of Spirits upon Bodies, or of Bodies upon Spirits; and yet most men admire nothing but this, believing to know the other: whereas he judges, that all things being well examin'd, the Action of Bodies upon Bodies is no more conceivable, than that of Spirits upon Bodies. Mean while the opinion of the Authour touching this subject, is, That the union of Soul and Body consists onely in this, that certain motions of the Body are followed by certain Cogitations of the Soul, and, on the contrary, that certain Thoughts of the Soul are follow'd by certain Motions of the Body. And, having supposed, that Bodies are said to act upon one another, when they cause some change suitable to Extension, and Spirits to act upon one another, when they cause some change suitable to a Thought; he infers, that when a Body acts upon a Spirit, that cannot be by causing any change of motion, of figure, or parts, as having none of all these; nor when a Spirit acts upon a Body, that cannot be by producing any change of Thought, as having none: But, when this Body, or its motion, or figure, or other thing, depending upon its nature, can be perceived by a Spirit, so as, upon that occasion, this Spirit has thoughts, it had not before, it may be said, that the Body has acted upon this Spirit, for as much as it has caused all the change in it, whereof it was capable according to its nature.

In the Sixth, After he hath shew'd, what is to be understood by what we call Soul, and by what we call Body, he labours to make it out, that we are much more assured of the Existence of the Soul, than of that of the Body, which he conceives he can prove from hence, that we cannot doubt, that we think, because even doubting is thinking; but one may doubt, whether one has a body, for several reasons, which he alledges, and thinks so cogent, that he concludes, it is not evident to him by the light of reason, that he has a Body. But supposing, there be Bodies, he examines, what are the Operations, that belong to the Soul, and what those, that belong to the Body; and lastly, what those, that result from the Union of both: And then explains, how all those operations are perform'd, and particularly, Sensation; where he shews, that the Nerves, holding at one end to the Brain, whereof they are but Allongations, and being at the other end extended to the extremities of the Body; when an Object comes to touch those exterior ends of the Nerves, the interior ones in the Brain are presently shaken, and cause different sensations according to the diversitie of Nerves, and the differing manner, in which they are shaken. And to shew, that 'tis this shaking, that causes Sensation, he notes, that if any thing shakes the interior parts of the Nerves, though the object be absent, the Soul has presently the same sensations as at would have, if it were present. As, if one should knock on's head forcibly against a wall, the shaking, which the blow gives to the Brain, moving the interior extremities of the Nerve, which causes the sensation of Light, the Soul has the same sensation, which it would have, if it saw a thousand Candles: On the contrary, if the interior extremities of the nerves are not shaken, though the object be present, it causes no sensation; whence it comes, that if a strong Ligature be made upon the middle of the Arm, and the hand be then prickt, no pain is felt, because the shaking of the nerves that are pricked, being stopped by the Ligature, cannot reach to the extremities of the Nerves, that are within the Brain.


The following Errata, left by the Press in Num. 16, the Reader is desired thus to correct.

Page 269. lin 27. read, motion of B. above the Center; G. is also, with a Semi-colon after the word Center. p. 274. l. 13. r. it to do to the. p. 277. l. 24. r. natural days. p. 281. l. 16. r. of his ib. l. 27. r. a notion. p. 293. l. 4. r. enough without. ib. l. 43. r. to the Sine of. p. 294. l. 1. r. to the Sine of.

Printed for John Martyn and James Allestry,

Printers to the Royal Society. 1666.