Lamarck, the Founder of Evolution Part 10

Thus littoral sh.e.l.ls of many genera, such as Pectens, Tellinae, c.o.c.kle sh.e.l.ls, turban sh.e.l.ls (_sabots_), etc., madrepores and other littoral polyps, the bones of marine or of amphibious animals which have lived near the sea, and which occur as fossils, are then unimpeachable monuments of the sojourn of the sea on the points of the dry parts of the globe where we observe their deposits, and besides these occur deep-water forms. "Thus the encrinites, the belemnites, the orthocerat.i.tes, the ostracites, the terebratules, etc., all animals which habitually live at the bottom, found for the most part among the fossils deposited on the point of the globe in question, are unimpeachable witnesses which attest that this same place was once part of the bottom or great depths of the sea." He then attempts to prove, and does so satisfactorily, that the sh.e.l.ls he refers to are what he calls deep-water (pelagiennes). He proves the truth of his thesis by the following facts:

1. We are already familiar with a marine Gryphaea, and different Terebratulae, also marine sh.e.l.l-fish, which do not, however, live near sh.o.r.e. 2. Also the greatest depth which has been reached with the rake or the dredge is not dest.i.tute of molluscs, since we find there a great number which only live at this depth, and without instruments to reach and bring them up we should know nothing of the _cones_, _olives_, Mitra, many species of Murex, Strombus, etc. 3.

Finally, since the discovery of a living Encrinus, drawn up on a sounding line from a great depth, and where lives the animal or polyp in question, it is not only possible to a.s.sure ourselves that at this depth there are other living animals, but on the contrary we are strongly bound to think that other species of the same genus, and probably other animals of different genera, also live at the same depths. All this leads one to admit, with Bruguiere,[78] the existence of deep-water sh.e.l.l-fish and polyps, which, like him, I distinguish from littoral sh.e.l.ls and polyps.

"The two sorts of monuments of which I have above spoken, namely, littoral and deep-sea fossils, may be, and often should be, found separated by different beds in the same bank or in the same mountains, since they have been deposited there at very different epochs. But they may often be found mixed together, because the movements of the water, the currents, submarine volcanoes, etc., have overturned the beds, yet some regular deposits in water always tranquil would be left in quite distant beds.... Every dry part of the earth's surface, when the presence or the abundance of marine fossils prove that formerly the sea has remained in that place, has necessarily twice received, for a single incursion of the sea, littoral sh.e.l.ls, and once deep-sea sh.e.l.ls, in three different deposits--this will not be disputed. But as such an incursion of the sea can only be accomplished by a period of immense duration, it follows that the littoral sh.e.l.ls deposited at the first sojourn of the edge of the sea, and const.i.tuting the first deposit, have been destroyed--that is to say, have not been preserved to the present time; while the deep-water sh.e.l.ls form the second deposit, and there the littoral sh.e.l.ls of the third deposit are, in fact, the only ones which now exist, and which const.i.tute the fossils that we see."

He again a.s.serts that these deposits could not be the result of any sudden catastrophe, because of the necessarily long sojourn of the sea to account for the extensive beds of fossil sh.e.l.ls, the remains of "infinitely multiplied generations of sh.e.l.led animals which have lived in this place, and have there successively deposited their debris." He therefore supposes that these remains, "continually heaped up, have formed these sh.e.l.l banks, become fossilized after the lapse of considerable time, and in which it is often possible to distinguish different beds." He then continues his line of anti-catastrophic reasoning, and we must remember that in his time facts in biology and geology were feebly grasped, and scientific reasoning or induction was in its infancy.

"I would again inquire how, in the supposition of a universal catastrophe, there could have been preserved an infinity of delicate sh.e.l.ls which the least shock would break, but of which we now find a great number uninjured among other fossils. How also could it happen that bivalve sh.e.l.ls, with which calcareous rocks and even those changed into a silicious condition are interlarded, should be all still provided with their two valves, as I have stated, if the animals of these sh.e.l.ls had not lived in these places?

"There is no doubt but that the remains of so many molluscs, that so many sh.e.l.ls deposited and consequently changed into fossils, and most of which were totally destroyed before their substance became silicified, furnished a great part of the calcareous matter which we observe on the surface and in the upper beds of the earth.

"Nevertheless there is in the sea, for the formation of calcareous matter, a cause which is greater than sh.e.l.led molluscs, which is consequently still more powerful, and to which must be referred ninety-nine hundredths, and indeed more, of the calcareous matter occurring in nature. This cause, so important to consider, is the existence of _coralligenous polyps_, which we might therefore call _testaceous polyps_, because, like the testaceous molluscs, these polyps have the faculty of forming, by a transudation or a continual secretion of their bodies, the stony and calcareous polypidom on which they live.

"In truth these polyps are animals so small that a single one only forms a minute quant.i.ty of calcareous matter. But in this case what nature does not obtain in any volume or in quant.i.ty from any one individual, she simply receives by the number of animals in question, through the enormous multiplicity of these animals, and their astonishing fecundity--namely, by the wonderful faculty they have of promptly regenerating, of multiplying in a short time their generations successively, and rapidly acc.u.mulating; finally, by the total amount of reunion of the products of these numerous little animals.

"Moreover, it is a fact now well known and well established that the coralligenous polyps, namely, this great family of animals with coral stocks, such as the millepores, the madrepores, astraeae, meandrinae, etc., prepare on a great scale at the bottom of the sea, by a continual secretion of their bodies, and as the result of their enormous multiplication and their acc.u.mulated generations, the greatest part of the calcareous matter which exists. The numerous coral stocks which these animals produce, and whose bulk and numbers perpetually increase, form in certain places islands of considerable extent, fill up extensive bays, gulfs, and roadsteads; in a word, close harbors, and entirely change the condition of coasts.

"These enormous banks of madrepores and millepores, heaped upon each other, covered and intermingled with serpulae, different kinds of oysters, patellae, barnacles, and other sh.e.l.ls fixed by their base, form irregular mountains of an almost limitless extent.

"But when, after the lapse of considerable time, the sea has left the places where these immense deposits are laid down, then the slow but combined alteration that these great ma.s.ses undergo, left uncovered and exposed to the incessant action of the air, light, and a variable humidity, changes them gradually into fossils and destroys their membranous or gelatinous part, which is the readiest to decompose. This alteration, which the enormous ma.s.ses of the corals in question continued to undergo, caused their structure to gradually disappear, and their great porosity unceasingly diminished the parts of these stony ma.s.ses by displacing and again bringing together the molecules composing them, so that, undergoing a new aggregation, these calcareous molecules obtained a number of points of contact, and const.i.tuted harder and more compact ma.s.ses. It finally results that instead of the original ma.s.ses of madrepores and millepores there occurs only ma.s.ses of a compact calcareous rock, which modern mineralogists have improperly called _primitive limestone_, because, seeing in it no traces of sh.e.l.ls or corals, they have mistaken these stony ma.s.ses for deposits of a matter primitively existing in nature."

He then reiterates the view that these deposits of marble and limestones, often forming mountain ranges, could not have been the result of a universal catastrophe, and in a very modern way goes on to specify what the limits of catastrophism are. The only catastrophes which a naturalist can reasonably admit as having taken place are partial or local ones, those dependent on causes acting in isolated places, such as the disturbances which are caused by volcanic eruptions, by earthquakes, by local inundations, by violent storms, etc. These catastrophes are with reason admissible, because we observe their a.n.a.logues, and because we know that they often happen. He then gives examples of localities along the coast of France, as at Manche, where there are ranges of high hills made up of limestones containing Gryphaeae, ammonites, and other deep-water sh.e.l.ls.

In the conclusion of the chapter, after stating that the ocean has repeatedly covered the greater part of the earth, he then claims that "the displacement of the sea, producing a constantly variable inequality in the ma.s.s of the terrestrial radii, has necessarily caused the earth's centre of gravity to vary, as also its two poles.[79]

Moreover, since it appears that this variation, very irregular as it is, not being subjected to any limits, it is very probable that each point of the surface of the planet we inhabit is really in the case of successively finding itself subjected to different climates." He then exclaims in eloquent, profound, and impa.s.sioned language:

"How curious it is to see that such suppositions receive their confirmation from the consideration of the state of the earth's surface and of its external crust, from that of the nature of certain fossils found in abundance in the northern regions of the earth, and whose a.n.a.logues now live in warm climates; finally, in that of the ancient astronomical observations of the Egyptians.

"Oh, how great is the antiquity of the terrestrial globe, and how small are the ideas of those who attribute to the existence of this globe a duration of six thousand and some hundred years since its origin down to our time!

"The physico-naturalist and the geologist in this respect see things very differently; for if they have given the matter the slightest consideration--the one, the nature of fossils spread in such great numbers in all the exposed parts of the globe, both in elevated situations and at considerable depths in the earth; the other, the number and disposition of the beds, as also the nature and order of the materials which compose the external crust of this globe studied throughout a great part of its thickness and in the mountain ma.s.ses--have they not had opportunities to convince themselves that the antiquity of this same globe is so great that it is absolutely beyond the power of man to appreciate it in an adequate way!

"a.s.suredly our chronologies do not extend back very far, and they could only have been made by propping them up by fables. Traditions, both oral and written, become necessarily lost, and it is in the nature of things that this should be so.

"Even if the invention of printing had been more ancient than it is, what would have resulted at the end of ten thousand years?

Everything changes, everything becomes modified, everything becomes lost or destroyed. Every living language insensibly changes its idiom; at the end of a thousand years the writings made in any language can only be read with difficulty; after two thousand years none of these writings will be understood. Besides wars, vandalism, the greediness of tyrants and of those who guide religious opinions, who always rely on the ignorance of the human race and are supported by it, how many are the causes, as proved by history and the sciences, of epochs after epochs of revolutions, which have more or less completely destroyed them.

"How many are the causes by which man loses all trace of that which has existed, and cannot believe nor even conceive of the immense antiquity of the earth he inhabits!

"How great will yet seem this antiquity of the terrestrial globe in the eyes of man when he shall form a just idea of the origin of living bodies, as also of the causes of the development and of the gradual process of perfection of the organization of these bodies, and especially when it will be conceived that, time and favorable circ.u.mstances having been necessary to give existence to all the living species such as we actually see, he is himself the last result and the actual maximum of this process of perfecting, the limit (_terme_) of which, if it exists, cannot be known."

In the fourth chapter of the book there is less to interest the reader, since the author mainly devotes it to a reiteration of the ideas of his earlier works on physics and chemistry. He claims that the minerals and rocks composing the earth's crust are all of organic origin, including even granite. The thickness of this crust he thinks, in the absence of positive knowledge, to be from three to four leagues, or from nine to twelve miles.

After describing the mode of formation of minerals, including agates, flint, geodes, etc., he discusses the process of fossilization by molecular changes, silicious particles replacing the vegetable or animal matter, as in the case of fossil wood.

While, then, the products of animals such as corals and molluscs are limestones, those of vegetables are humus and clay; and all of these deposits losing their less fixed principles pa.s.s into a silicious condition, and end by being reduced to quartz, which is the earthy element in its purest form. The salts, pyrites, and metals only differ from other minerals by the different circ.u.mstances under which they were acc.u.mulated, in their different proportions, and in their much greater amount of carbonic or acidific fire.

Regarding granite, which, he says, naturalists very erroneously consider as _primitive_, he begins by observing that it is only by conjecture that we should designate as primitive any matter whatever. He recognizes the fact that granite forms the highest mountains, which are generally arranged in more or less regular chains. But he strangely a.s.sumes that the const.i.tuents of granite, _i.e._, felspar, quartz, and mica, did not exist before vegetables, and that these minerals and their aggregation into granite were the result of slow deposition in the ocean.[80] He goes so far as to a.s.sert that the porphyritic rocks were not thus formed in the sea, but that they are the result of deposits carried down by streams, especially torrents flowing down from mountains. Gneiss, he thinks, resulted from the detritus of granitic rocks, by means of an inappreciable cement, and formed in a way a.n.a.logous to that of the porphyries.

Then he attacks the notion of Leibnitz of a liquid globe, in which all mineral substances were precipitated tumultuously, replacing this idea by his chemical notion of the origin of the crystalline and volcanic rocks.

He is on firmer ground in explaining the origin of chalk and clay, for the rocks of the region about Paris, with which he was familiar, are sedimentary and largely of organic origin.

In the "Addition" (pp. 173-188) following the fourth chapter Lamarck states that, allowing for the variations in the intensity of the cause of elevation of the land as the result of the acc.u.mulations of organic matter, he thinks he can, without great error, consider the mean rate as 324 mm. (1 foot) a century. As a concrete example it has been observed, he says, that one river valley has risen a foot higher in the s.p.a.ce of eleven years.

Pa.s.sing by his speculations on the displacement of the poles of the earth, and on the elevations of the equatorial regions, which will dispense with the necessity of considering the earth as originally in a liquid condition, he allows that "the terrestrial globe is not at all a body entirely and truly solid, but that it is a combination (_reunion_) of bodies more or less solid, displaceable in their ma.s.s or in their separate parts, and among which there is a great number which undergo continual changes in condition."

It was, of course, too early in the history of geology for Lamarck to seize hold of the fact, now so well known, that the highest mountain ranges, as the Alps, Pyrenees, the Caucasus, Atlas ranges, and the Mountains of the Moon (he does not mention the Himalayas) are the youngest, and that the lowest mountains, especially those in the more northern parts of the continents, are but the roots or remains of what were originally lofty mountain ranges. His idea, on the contrary, was, that the high mountain chains above mentioned were the remains of ancient equatorial elevations, which the fresh waters, for an enormous mult.i.tude of ages, were in the process of progressively eroding and wearing down.

What he says of the formation of coal is noteworthy:

"Wherever there are ma.s.ses of fossil wood buried in the earth, the enormous subterranean beds of coal that are met with in different countries, these are the witnesses of ancient encroachments of the sea, over a country covered with forests; it has overturned them, buried them in deposits of clay, and then after a time has withdrawn."

In the appendix he briefly rehea.r.s.es the laws of evolution as stated in his opening lecture of his course given in the year IX. (1801), and which would be the subject of his projected work, _Biologie_, the third and last part of the Terrestrial Physics, a work which was not published, but which was probably comprised in his _Philosophie zoologique_.

The _Hydrogeologie_ closes with a "_Memoire sur la matiere du feu_" and one "_sur la matiere du son_," both being reprinted from the _Journal de Physique_.

FOOTNOTES:

[60] _Evolution in Biology_, in _Darwiniana_, New York, 1896, p. 212.

[61] _Principles of Geology_.

[62] Lyell's _Principles of Geology_, 8th edit., p. 22.

[63] Quoted from Flourens' _eloge Historique de Georges Cuvier_, Hoefer's edition. Paris, 1854.

[64] _Remarques sur les Coquilles fossiles de quelques Cantons de la Touraine_. Mem. Acad. Sc. Paris, 1720, pp. 400-417.

[65] _eloge Historique de Werner_, p. 113.

[66] _History of Civilization_, i. p. 627.

[67] _France under Louis XV._, p. 359.

[68] _France under Louis XV._, p. 360.

[69] See vol. iii. of his _Memoires sur differentes Parties des Sciences et des Arts_, pp. 209-403. Geikie does not give the date of the third volume of his work, but it was apparently about 1771, as vol. ii. was published in 1770. I copy Geikie's account of Guettard's observations often in his own words.

[70] Lyell's _Principles of Geology_.

[71] Geikie states that the doctrine of the origin of valleys by the erosive action of the streams which flow through them, though it has been credited to various writers, was first clearly taught from actual concrete examples by Desmarest. _L. c._, p. 65.

[72] Jameson's _Cuvier's Theory of the Earth_, New York, 1818.

[73] J. G. Lehmann of Berlin, in 1756, first formally stated that there was some regular succession in the strata, his observations being based on profiles of the Hartz and the Erzgebirge. He proposed the names Zechstein, Kupferschiefer, rothes Todtliegendes, which still linger in German treatises. G. C. Fuchsel (1762) wrote on the stratigraphy of the coal measures, the Permian and the later systems in Thuringia. (Zittel.)