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Popular Science Monthly/Volume 20/November 1881/Editor's Table

< Popular Science Monthly‎ | Volume 20‎ | November 1881

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EDITOR'S TABLE.

BALANCE AND COMPENSATION OF INORGANIC FORCES.

IT was some forty years ago that the organic chemists, represented by such masters as Dumas and Liebig, worked out the beautiful idea of the balance of organic nature. They showed that the vegetable and animal kingdoms carry on antagonist processes—each for ever undoing the work of the other. The atmosphere is the arena of this subtile conflict, being poisoned by the animal world and purified by the vegetable world; while these opposing processes so effectually counteract each other, that the air is automatically maintained in a condition fitted for the preservation of the living races.

A corresponding balance of forces is displayed on a grand and still more striking scale in the inorganic world, by which the varied configuration of the earth's surface and the continued habitability of the globe are maintained. ​In his new and very interesting book on "Volcanoes," Professor J. W. Judd, of London, has taken up this subject, and his chapter on "The Part played by Volcanoes in the Economy of Nature" impresses us like a powerful sermon on the old problem of good and evil—and that has also something new in it. Professor Judd does not dwell upon the moral aspect of the subject, but we can not better introduce his view to our readers than by a reference to its ethical implications.

Nothing, of course, can have less claim upon the attention of men whose intelligence, however considerable of its sort, has never been directed to the understanding of nature, than what goes on in the interior of the earth. That, says a representative of this class, belongs to scientific speculation, and is no concern of his. He knows, indeed, of earthquakes and volcanoes as deadly agencies by which great numbers of lives are often ruthlessly destroyed; and he regards them as conspicuous examples of diabolism in nature; and when he hears it said that "volcanoes are the safety-valves of the globe," he is very glad to know that they have some possible use, however remote.

Now, ethics—the science of right and wrong, of good and bad—is certainly not an exact science; and yet it has a quantitative basis. In the constitution of this world, good and evil are inextricably mixed up, and the problem of their proportions is therefore fundamental in ethical inquiries. There is always more or less of each, and there are degrees of both. We are familiar with the terms small and great in their applications to evil and good, and we labor to diminish the former and increase the latter. It is natural that the estimates of the relative amounts of good and evil should vary, especially as so much depends upon the subjective condition of the estimator. The pessimist admits that there may be hours and perhaps places in which good prevails; but he maintains that, on the whole, evil so greatly predominates that life is not worth living. The optimist holds on the contrary that, while evil may be supreme at times, good is ascendant in the large view. The question between them, therefore, is mainly one of relative quantities.

If, now, it can be shown that in any given case good prevails over evil, say in the ratio of one hundred thousand to one, it is obvious that the pessimist will not have much margin left upon which to make a stand; and, if it can be further proved that this ratio holds on a stupendous scale, and, moreover, that it includes just those malign manifestations of Nature that are most cited as evidence of her vicious spirit, the pessimist will be left in a still worse predicament. This position may be familiarly illustrated. A certain considerable amount of life is violently destroyed each year by lightnings, storms, and floods; yet these effects are only the calamitous incidents of a great system of circulation of water and air over our globe by which all life is maintained. That system of movements gives good and evil, but, compared with their beneficence, the disastrous results they produce are absolutely insignificant. If we say that the good prevails over the evil at the rate of a million to one, the estimate is still very far within the limits of truth.

Professor Judd has shown that the same principle holds in regard to volcanoes and earthquakes. We know that by these agencies dwellings, villages, and even entire cities are reduced to heaps of ruins, often with the direct destruction of multitudes of people, and furthermore that famines, pestilences, and social disorganizations frequently follow. But these catastrophes, terrible as they may be, are the results of a system of overwhelming beneficence. The subterranean energies, of which earthquakes and volcanoes are the striking manifestations, are necessary to ​the continued existence of our earth as a place fitted for the habitation of living beings, and they must be credited with the total amount of benefit implied by the existence and preservation of the life of the globe in all its forms and gradations. We quote enough of the argument of Professor Judd, in his elaborate chapter upon this subject, to substantiate the view here taken:

We have had frequent occasion in the preceding pages to refer to the work—slow hut sure, silent but effective—wrought by the action of the denuding forces ever operating upon the surface of our globe. The waters condensing from the atmosphere and, falling upon the land in the form of rain, snow, or hail, are charged with small quantities of dissolved gases, and these waters, penetrating among the rock-masses of which the earth's crust is composed, give rise to various chemical actions of which we have already noticed such remarkable illustrations in studying the ancient volcanic products of our globe. By this action the hardest and most solid rock masses are reduced to a state of complete disintegration, certain of their ingredients undergoing decomposition, and the cementing materials which hold their particles together being removed in a state of solution. In the higher regions of the atmosphere this work of rock-disintegration proceeds with the greatest rapidity; for there the chemical action is reënforced by the powerful mechanical action of freezing water. On high mountain-peaks the work of breaking up rock-masses goes on at the most rapid rate, and every craggy pinnacle is swathed by the heaps of fragments which have fallen from it. The Alpine traveler justly dreads the continual fusillade of falling rock-fragments which is kept up by the ever-active power of the frost in these higher regions of the atmosphere; and fears lest the vibrations of his footsteps should loosen, from their position of precarious rest, the rapidly accumulating piles of detritus. No mountain-peak attains to any very great elevation above the earth's surface, for the higher we rise in the atmosphere the greater is the range of temperature and the more destructive are the effects of the atmospheric water. The moon, which is a much smaller planet than our earth, has mountains of far greater elevation; but the moon possesses neither an atmosphere nor moisture on its surface, to produce those leveling effects which we see everywhere going on around us upon the earth.

The disintegrated materials, produce 1 by chemical and mechanical actions of the atmospheric waters upon rock-masses, are by floods, rivers, and glaciers, gradually transported from higher to lower levels; and sooner or later every fragment, when it has once been separated from a mountain-top, must reach the ocean, where these materials are accumulated and arranged to form new rocks. Over every part of the earth's surface these three grand operations of the disintegration of old rock-masses, the transport of the materials so produced to lower levels, and the accumulation of these materials to form new rocks, are continually going on. It is by the varied action of these denuding agents upon rocks of unequal hardness, occupying different positions in relation to one another, that all the external features of hills, and plains, and mountains owe then-origin.

It is a fact, which is capable of mathematical demonstration, that by the action of these denuding forces the surface of all the lands of the globe is being gradually but surely lowered; and this takes place at such a rate that in a few millions of years the whole of the existing continents must be washed away and their materials distributed over the beds of the oceans.

It is evident that there exists some agency by which this leveling action of the denuding forces of the globe is compensated; and a little consideration will show that such compensating agency is found in the subterranean forces ever at work within the earth's crust. The effects of these subterranean forces which most powerfully arrest our attention are volcanic outbursts and earthquake shocks, but a careful study of the subject proves that these are by no means the most important of the results of the action of such forces. Exact observation has proved that almost every part of the earth's surface is either rising or falling, and the striking and destructive phenomena of volcanoes and earthquakes probably bear only the same relation to those grand and useful actions of the subterranean forces which floods do to the system of circulating waters and hurricanes to the system of moving air-currents. . . .

We establish the fact of the movement of portions of the earth's crust by noticing the changing positions of parts of the earth's surface in relation to the constant level of the ocean. When this is done we find abundant proof that, while some parts of the earth's crust are rising, others are as undoubtedly undergoing depression.

We shall be able to form some idea of the vastness of the effects produced by the ​subterranean forces, by a very simple consideration. It is certain that during, the enormous periods of time of which the records have been discovered by the geologist, there have always been continents and oceans upon the earth's surface, just as at present, and it is almost equally certain that the proportions of the earth's surface occupied by land and water respectively have not varied very widely from those which now prevail. But, at the same time, it is an equally well-established fact that the denuding forces ever at work upon the earth's surface would have been competent to the removal of existing continents many times over, in the vast periods covered by geological records. Hence we are driven to conclude that the subterranean movements have in past times entirely compensated for the waste produced by the denuding forces ever at work upon our globe. But this is not all. The subterranean forces not only produce upheaval; in a great many cases the evidences of subsidence are as clear and conclusive as are those of upheaval in others. Hence we are driven to conclude that the forces producing upheaval of portions of the earth's crust are sufficient, not only to balance those producing subsidence, but also to compensate for the destructive action of denuding agents upon the land-masses of the globe.

It is only by a careful and attentive study and calculation of the effects produced by the denuding agents at work all around us, aided by an examination of the enormous thicknesses of strata formed by the action of such causes during past geological times, that we are able to form any idea of the reality and vastness of the agents of change which are ever operating to modify the earth's external features. When we have clearly realized the grand effects produced on the surface of the globe by these external forces, through the action of its investing atmosphere and circulating waters, then, and only then, shall we be in a position to estimate the far greater effects resulting from the internal forces, of which the most striking, but not the most important, results are seen in the production of volcanic eruptions and earthquake-shocks.

Another series of facts which serves to convince the geologist of the reality and potency of the forces ever at work within the earth's crust, and the way in which these have operated during past geological periods, is found in the disturbed condition of many of the stratified rock-masses which it is composed. Such stratified rock-masses, it is clear, must have been originally deposited in a position of approximate horizontality; but they arc now often found in inclined and even vertical positions; they are seen to be bent, crumpled, puckered, and folded in the most remarkable manner, and have not unfrequently been broken across by dislocations—"faults"—which have sometimes displaced masses, originally in contact, to the extent of thousands of feet. The slate-rocks of the globe, moreover, bear witness to the fact that strata have been subjected to the action of lateral compression of enormous violence and vast duration; while in the metamorphic rocks we see the effects of still more extreme mechanical strains, which have been in part transformed into chemical action. No one who has not studied the crushed, crumpled, fractured, and altered condition of many of the sedimentary rocks of the globe, can form the faintest idea of the enormous effects of the internal forces which have been in operation within the earth's crust during earlier geological periods. And it is only by such studies as these that we at last learn to regard the earthquake and volcanic phenomena of our globe, not as the grandest and most important effects of these forces, but as their secondary and accidental accompaniments.

Professor Judd here passes to a very lucid presentation of the later views of geologists in regard to the mode of origin and development of mountains. This is an important part of his discussion, hut we have no room for it here. He concludes:

From what has been said, it will be seen that mountain-chains may be regarded as cicatrized wounds in the earth's solid crust. A line of weakness first betrays itself at a certain part of the earth's surface by fissures, from which volcanic outbursts take place; and thus the position of the future mountain chain is determined. Next, subsidence during many millions of years permits of the accumulation of the raw materials out of which the mountain-range is to be formed; subsequent earth-movements cause these raw materials to be elaborated into the hardest and most crystalline rock-masses, and place them in elevated and favorable positions; and lastly, denudation sculptures from these hardened rock-masses all the varied mountain forms. Thus the work of mountain-making is not, as was formerly supposed by geologists, the result of a simple upheaving force, but is the outcome of a long and complicated series of operations.

The careful study of other mountain chains, especially those of the American ​Continent, has shown that the series of actions which we have described as occurring in the Alps took place in the same order in the formation of all mountain-masses. It is doubtful whether the line of weakness is always betrayed in the first instance by the formation along its course of volcanic fissures. But in all cases we have evidence of the production of a geosynclinal, which is afterward, by lateral pressure, converted into a geanticlinal, and from this the mountain-chains have been carved by denudation. Professor Dana has shown that the geosynclinal of the Appalachian chain was made up of sediments attaining a thickness of forty thousand feet, or eight miles; while Mr. Clarence King has shown that a part of the geosynclinal of the Rocky Mountains was built up of no less than sixty thousand feet, or twelve miles of strata.

It has thus been established that a very remarkable relation exists between the forces by which continental masses of land are raised and depressed and mountain-ranges have been developed along lines of weakness separating such moving continental masses and those more sudden and striking manifestations of energy which give rise to volcanic phenomena. It is in this relation between the widespread subterranean energies and the local development of the same forces at volcanic vents that we must in all probability seek for the explanation of those interesting peculiarities of the distribution of volcanoes upon the face of the globe which we have described in a former chapter. The parallelism of volcanic bands to great mountain-chains is thus easily accounted for; and in the same way we may probably explain the position of most volcanoes with regard to coast-lines. . . .

Terrible and striking, then, as are the phenomena connected with volcanic action, such sudden and violent manifestations of the subterranean energy must not be regarded as the only, or indeed the chief, effects which they produce. The internal forces continually at work within the earth's crust perform a series of most important functions in connection with the economy of the globe, and, were the action of these forces to die out, our planet would soon cease to be fit for the habitation of living beings. . . .

It is by no means a difficult task to calculate the approximate rate at which the various continents and islands are being leveled down, and such calculations prove that in a very few millions of years the existing forces operating upon the earth's surface would reduce the whole of the land-masses to the level of the ocean. . . .

But, by the admirable balancing of the external and internal forces on our own globe, the conditions necessary to animal and vegetable existence are almost constantly maintained, and those interruptions of such conditions, produced by hurricanes and floods, by volcanic outbursts and earthquakes, may safely be regarded as the insignificant accidents of what is, on the whole, a very perfectly working piece of machinery.


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