Kitobni o'qish: «Buffon's Natural History, Volume I (of 10)», sahifa 10
The different strata of which the earth is composed are not disposed according to their specific weight, for we often find strata of heavy matters placed on those of lighter. To be assured of this, we have only to examine the earth on which rocks are placed, and we shall find that it is generally clay or sand, which is specifically lighter. In hills, and other small elevations, we easily discover this to be the case; but it is not so with large mountains, for not only their summits are rocks, but those rocks are placed on others; there mountains are placed upon mountains, and rocks upon rocks, to such a considerable height, and through so great an extent of country, that we can scarcely be certain whether there is earth at bottom, or of what nature it is. I have seen cavities made in rocks to some hundred feet deep, without being able to form an idea where they ended, for these rocks were supported by others; nevertheless, may we not compare great with small? and since the rocks of little mountains, whose bases are to be seen, rest on the earth less heavy and solid than stone, may we not suppose that earth is also the base of high mountains? All that I have here to prove by these arguments is, that, by the motion of the waters, it may naturally happen that the more ponderous matters accumulated on the lighter; and that, if this in fact is found to be so in most hills, it is probable that it happened as explained by my theory; but should it be objected that I am not grounded in supposing, that before the formation of mountains the heaviest matters were below the lighter; I answer, that I assert nothing general in this respect, because this effect may have been produced in many manners, whether the heaviest matters were uppermost or undermost, or placed indiscriminately. To conceive how the sea at first formed a mountain of clay, and afterwards capt it with rocks, it is sufficient to consider the sediments may successively come from different parts, and that they might be of different materials. In some parts, the sea may at first have deposited sediments of clay, and the waters afterwards brought sediment of strong matter, either because they had transported all the clay from the bottom and sides, and then the waves attacked the rocks, possibly because the first sediment came from one part, and the second from another. This perfectly agrees with observation, by which we perceive that beds of earth, stone, gravel, sand, &c. followed no rule in their arrangement, but are placed indifferently one on the other as it were by chance.
But this chance must have some rules, which can be known only by estimating the value of probabilities, and the truth of conjectures. According to our hypothesis, on the formation of the globe, we have seen that the interior part of the globe must have been a vitrified matter, similar to vitrified sand, which is only the fragments of glass, and of which the clays are perhaps the scoria; by this supposition, the centre of the earth, and almost as far as the external circumference, must be glass, or a vitrified matter; and above this we shall find sand, clay, and other scoria. Thus the earth, in its first state, was a nucleus of glass, or vitrified matter; either massive like glass, or divided like sand, because that depends on the degree of heat it has undergone. Above this matter was sand, and lastly clay. The soil of the waters and air produced the external crust, which is thicker or thinner, according to the situation of the ground; more or less coloured, according to the different mixtures of mud, sand, clay, and the decayed parts of animals and vegetables; and more or less fertile, according to the abundance or want of these parts. To shew that this supposition on the formation of sand and clay is not chimerical, I shall add some particular remarks.
I conceive, that the earth, in its first state, was a globe, or rather a spheroid of compact glass, covered with a light crust of pumice stone and other scoria of the matter in fusion. The motion and agitation of the waters and air soon reduced this crust into powder or sand, which, by uniting afterwards, produced flints, and owe their hardness, colour, or transparency and variety, to the different degrees of purity of the sand which entered into their composition.
These sands, whose constituting parts unite by fire, assimilate, and become very dense, compact, and the more transparent as the sand is more pure; on the contrary, being exposed a long time to the air, they disunite and exfoliate, descend in the form of earth, and it is probable the different clays are thus produced. This dust, sometimes of a brightish yellow, and sometimes like silver, is nothing else but a very pure sand somewhat perished, and almost reduced to an elementary state. By time, particles will be so far attenuated and divided, that they will no longer have power to reflect the light, and acquire all the properties of clay.
This theory is conformable to what every day is seen; let us immediately wash sand upon its being dug, and the water will be loaded with a black ductile and fat earth, which is genuine clay. In streets paved with freestone, the dirt is always black and greasy, and when dried appears to be an earth of the same nature as clay. Let us wash the earth taken from a spot where there are neither freestone nor flints, and there will always precipitate a great quantity of vitrifiable sand.
But what perfectly proves that sand, and even flint and glass, exist in clay, is, that the action of fire, by uniting the parts, restores it to its original form. Clay, if heated to the degree of calcination, will cover itself with a very hard enamel; if it is not vitrified internally, it nevertheless will have acquired a very great hardness, so as to resist the file; it will emit fire under the hammer, and it has all the properties of flint; a greater degree of heat causes it to flow, and converts it into real glass.
Clay and sand are therefore matters perfectly analogous, and of the same class; if clay, by condensing, may become flint and glass, why may not sand, by dissolution, become clay? Glass appears to be true elementary earth, and all mixed substances disguised glass. Metals, minerals, salts, &c. are only vitrifiable earth; common stone and other matters analogous to it, and testaceous and crustaceous shells, &c. are the only substances which cannot be vitrified, and which seem to form a separate class. Fire, by uniting the divided parts of the first, forms an homogeneous matter, hard and transparent, without any diminution of weight, and to which it is not possible to cause any alteration; those, on the contrary, in which a greater quantity of active and volatile principles enter, and which calcine, lose more than one-third of their weight in the fire, and retake the form of simple earth, without any other alteration than a disunion of their different parts: these bodies excepted, which are no great number, and whose combinations produce no great varieties in nature, every other substance, and particularly clay, may be converted into glass, and are consequently only decomposed glass. If the fire suddenly causes the form of these substances to change, by vitrifying them, glass itself, whether pure, or in the form of sand or flint, naturally, but by a slow and insensible progress, changes into clay.
Where flint is the predominant stone, the country is generally strewed with parts of it, and if the place is uncultivated, and these stones have been long exposed to the air, without having been stirred, their upper superficies is always white, whereas the opposite side, which touches the earth, is very brown, and preserves its natural colour. If these flints are broken, we shall perceive that the whiteness is not only external, but penetrates internally, and there forms a kind of band, not very deep in some, but which in others occupies almost the whole flint. This white part is somewhat grainy, entirely opaque, as soft as freestone, and adheres to the tongue like the boles; whereas the other part is smooth, has neither thread nor grain, and preserves its natural colour, transparency, and hardness. If this flint is put into a furnace, its white part becomes of a brick colour, and its brown part of a very fine white. Let us not say with one of our most celebrated naturalists, that these stones are imperfect flints of different ages, which have not acquired their perfection; for why should they be all imperfect? Why should they be imperfect only on the side exposed to the weather? It, on the contrary, appears to me more reasonable that they are flints changed from their original state, gradually decomposed, and assuming the form and property of clay or bole. If this is thought to be only conjecture, let the hardest and blackest flint be exposed to the weather, in less than a year its surface will change colour; and if we have patience to pursue this experiment, we shall see it by degrees lose its hardness, transparency, and other specific characters, and approach every day nearer and nearer the nature of clay.
What happens to flint happens to sand; each grain of sand may possibly be considered as a small flint, and each flint as a mass of extremely fine grains of sand. The first example of the decomposition of sand is found in the brilliant opaque powder called Mica, in which clay and slate are always diffused. The entirely transparent flints, the Quartz, produce, by decomposition, fat and soft talks, such as those of Venice and Russia, which are as ductile and vitrifiable as clay: and it appears to me, that talk is a mediate between glass, or transparent flint, and clay; whereas coarse and impure flint, by decomposing, passes to clay without any intermedium.
Our factitious glass undergoes the same alterations: it decomposes and perishes, as it were, in the air. At first, it assumes a variety of colours, then exfoliates, and by working it, we perceive brilliant scales fall off; but when its decomposition is more advanced, it crumbles between the fingers, and is reduced into a very white fine talky powder. Art has even imitated nature in the decomposition of glass and flint. "Est etiam certa methodus solius aquæ communis ope, silices & arenam in liquorem viscosum, eumdemque in sal viride convertendi, & hoc in aleum rubicundum, &c. Solius ignis & aqua ope, speciali experimento, durissimos quosque lapides in mucorem resolvo, qui distillan subtilem spiritum exhibet & oleum nullus laudibus prœdicabile24."
These matters more particularly belong to metals, and when we come to them, shall be fully treated on, therefore we shall content ourselves here with adding, that the different strata which cover the terrestrial globe, being materials to be considered as actual vitrifications or analogous to glass, and possessing its most essential qualities; and as it is evident, that from the decomposition of glass and flint, which is every day made before our eyes, a genuine clay remains, it is not a precarious supposition to advance, that clays and sands have been formed by scoria, and vitrified drops of the terrestrial globe, especially when we join the proofs a priori, which we have given to evince the earth has been in a state of liquefaction caused by fire.
ARTICLE VIII.
ON SHELLS, AND OTHER MARINE PRODUCTIONS FOUND IN THE INTERIOR PARTS OF THE EARTH
I have often examined quarries, the banks of which were filled with shells; I have seen entire hills composed of them, and chains of rocks which contained them throughout their whole extent. The quantity of these marine productions is astonishing, and the number in many places so prodigious, that it appears scarcely possible that any should now remain in the sea; it is by considering this innumerable multitude of shells, that no doubt is left of our earth having been a long time under the water of the ocean. The quantity found in a fossil, or petrified state, is beyond conception, and it is only from the number of those that have been discovered that we could possibly have formed an idea of their multiplicity. We must imagine, like those who reason on matters they never saw, that shells are only found at random, dispersed here and there, or in small heaps, as oyster shells thrown before our doors; on the contrary, they form mountains, are met with in shoals of 100 or 200 miles length, nay, they may sometimes be traced through whole provinces in masses of 50 or 60 feet thick. It is from these circumstances alone that we can reason on the subject.
We cannot give a more striking example on this subject than the shells of Touraine. The following is the description given of them by the historian of the Academy25.
"The number of figured stones and fossil shells found in the bowels of the earth were remarked in all ages and nations, but they were considered merely as the sports of nature, and even by philosophers themselves, as the productions of chance or accident; they regarded them with a degree of surprise, but passed them over with a slight attention, and all this phenomena perished without any fruit for the progress of knowledge. A potter in Paris, who knew neither Latin nor Greek, towards the end of the 16th century, was the first man who dared affirm, in opposition to the learned, that the fossil shells were real shells formerly deposited by the sea in those places where they were found; that animals, and particularly fish, had given to stones all these different figures, &c. and he desired the whole school of Aristotle to contradict his proofs. This was Bernard Palissy, as great a natural genius as nature could form: his system slept near 100 years, and even his name was almost forgot. At length the ideas of Palissy were revived in the mind of several philosophers; and science has profited by all the shells and figured stones the earth furnishes us with; perhaps they are at present become only too common, and the consequences drawn from them too incontestable.
"Notwithstanding this, the observations presented by M. Reaumer must appear wonderful. He discovered a mass of 130 million, 680 thousand cubical fathoms of shells, either whole or in fragments, without any mixture of stone, earth, sand, or other extraneous matter: hitherto fossil shells have never appeared in such an enormous quantity, nor without mixture. It is in Touraine this prodigious mass is found, more than 36 leagues from the sea; this is perfectly known there, as the farmers of that province make use of these shells, which they dig up, as manure for their lands, to fertilize their plains, which otherwise would be absolutely sterile.
"What is dug from the earth, and which generally is no more than eight or nine feet deep, are only small fragments of shells, very distinguishable as fragments, for they retain their original channels and hollows, having only lost their gloss and colour, as almost all shells do which we find in the earth. The smallest pieces, which are only dust, are still distinguishable because they are perfectly of the same matter as the rest, as well as of the whole shells which are sometimes found. We discover the species as well in the whole shells as in the larger fragments. Some of these species are known at Poictou, others belong to more remote coasts. There are even fragments of madrepores, coral, and other productions of the sea; all this matter in the country is termed Fallun, and is found wherever the ground is dug in that province for the space of nine leagues square. The peasants do not dig above twenty feet deep, because they think it would not repay them for their trouble, but they are certainly deeper. The calculation of the quantity is however taken upon the supposition of only 18 feet and 2200 fathoms to the league. This mass of shells of course exceeds the calculation, and possibly contains double the quantity.
"In physical points the smallest circumstances, which most people do not think worthy of remarking, sometimes lead to consequences and afford great lights. M. de Reaumer observed, that all these fragments of shells lie horizontally, and hence he has concluded that this infinity of fragments does not proceed from the heap being formed at one time, or of whole shells, for the uppermost, by their weight, would have crushed the others, and of course their fallings would have given an infinity of different positions. They must, therefore, have been brought there by the sea, either whole or broken, and necessarily placed horizontal; and although the extreme length of time was of itself sufficient to break, and almost calcine the greatest part, it could not change their position.
"By this it appears, that they must have been brought gradually, and, in fact, how was it possible that the sea could convey at once such an immense quantity of shells, and at the same time preserve a position perfectly horizontal? they must have collected in one spot, and consequently this spot must have been the bottom of a gulph or basin.
"All this proves, that although there must remain upon the earth many vestiges of the universal deluge, as recorded in scripture, the mass of shells at Touraine was not produced by that deluge; there is perhaps not so great a mass in any part of the sea; but even had the deluge forced them away, it would have been with an impetuosity and violence that would not have permitted them to retain one uniform position. They must have been brought and deposited gently and slowly, and consequently their accumulation required a space of time much longer than a year."
The surface of the earth, it is evident, must have been before or after the deluge very differently disposed to what it is at present, that the sea and continent had another arrangement, and formerly there was a great gulph in the middle of Touraine. The changes which are known from history, or even ancient fable, are inconsiderable, but they give us room to imagine those which a longer time might bring about. M. de Reaumur supposes that Touraine was a gulph of the sea which communicated with the ocean, and that the shells were carried there by a current; but this is a simple conjecture laid down in room of the real unknown fact. To speak with certainty on this matter, we should have geographical maps of all the places where shells have been dug from the earth, to obtain which would require almost an infinity of time and observation, yet it is possible that hereafter science may accomplish it.
This quantity of shells, considerable as it is, will astonish us less if we consider the following circumstances: first, shell fish multiply prodigiously, and are full grown in a very short time; the abundance of individuals in each kind proves to us their fertility. We have a strong example of this increase in oysters, a mass of many fathoms of which are frequently raised in a single day. In a very short time the rocks to which they are attached are considerably diminished, and some banks quite exhausted, nevertheless the ensuing year we find them as plentiful as before, nor do they appear to be in the least diminished; indeed I know not whether a natural bed of oysters was ever entirely exhausted. Secondly, the substance of shells is analogous to stone; they are a long time preserved in soft matters, and petrify readily in hard; these shells and marine productions therefore found on the earth, being the wrecks of many ages, must of course have formed very considerable masses.
There are a prodigious quantity of shells in marble, lime, stone, chalk, marl, &c. we find them, as before observed, in hills and mountains, and they often make more than one half of the bodies which contain them; for the most part they appear well preserved, others are in fragments, but large enough to distinguish to what kind of shells they belong. Here our knowledge on this subject, from observation, finds its limits; but I shall go further and assert that shells are the intermedium which Nature adopts for the formation of most kind of stones; that chalks, marls, and lime-stone are composed only of the powder and pieces of shells; that consequently the quantities of shells destroyed are infinitely more considerable than those preserved. I shall here content myself with indicating the point of view in which we ought to consider the strata of which the globe is composed. The first stratum is composed of the dust of the air, the sediment of the rain, dew, and vegetable or animal parts, reduced to particles; the strata of chalk, marl, lime, stone, and marble, are composed of the ruins of shells, and other marine productions, mixed with fragments or whole shells; but the vitrifiable sand or clay are the matters of which the internal parts of the globe are composed. They were vitrified when the globe received its form, which necessarily supposes that the matter was in fusion. The granate, rock, flint, &c. owe their origin to sand and clay, and are likewise disposed by strata; but tuffa26, free-stone, and flints (not in great masses), crystals, metals, pyrites, most minerals, sulphurs, &c. are matters whose formation is novel, in comparison with marbles, calcinable stones, chalk, marl, and all other materials disposed in horizontal strata, and which contain shells and other productions of the sea.
As the denominations I make use of may appear obscure or equivocal, it is necessary to explain them. By the term clay, I mean not only the white and yellow, but also blue, soft, hard, foliated, and other clays, which I look on as the scoria of glass, or as decomposed glass. By the word sand I always understand vitrifiable sand; and not only comprehend under this denomination the fine sand which produces freestone, and which I look upon as powdered glass, or rather pumice stone, but also the sand which proceeds from the freestone destroyed by friction, and also the larger sand, as small gravel, which proceeds from the granate and rock-stone, and is sharp, angular, red, and commonly found in the bed of rivers or rivulets that derive their waters immediately from the higher mountains, or hills composed of stone or granate. The river Armanson conveys a great quantity of this sand; it is large and brittle, and in fact is only fragments of rock-stone, as calcinable gravel is of freestone. Rock-stone and granate are one and the same substance, but I have used both denominations, because there are many persons who make two different species of them. It is the same with respect to flints and free-stone in large pieces; I look on them as kinds of granate, and I call them large flints, because they are disposed like calcinable stone in strata, and to distinguish them from the flints and free-stone in small masses, and the round flints which have no regular quarries, and whose beds have a certain extent; these are of a modern formation, and have not the same origin as the flints and free-stone in large lumps, which are disposed in regular strata.
I understand by the term slate, not only the blue, which all the world knows, but white, grey, and red slate: these bodies are generally met with below laminated clay, and have every appearance of being nothing more than clay hardened in this strata. Pit coal and jet are matters which also belong to clay, and are commonly under slate. By the word tuffa, I understood not only the common pumice which appears full of holes, and, as I may say, organized, but all the beds of stone made by the sediment of running waters, all the stalactites, incrustations, and all kinds of stone that dissolve by fire. It is no ways doubtful that these matters are not modern, and that they every day grow. Tuffa is only a mass of lapidific matter in which we perceive no distinct strata: this matter is disposed generally in small hollow cylinders, irregularly grouped and formed by waters dropt at the foot of mountains, or on the slope of hills, which contain beds of marl or soft and calcareous earth; these cylinders, which make one of the specific characters of this kind of tuffa, is either oblique or vertical according to the direction of the streams or water which form them. These sort of spurious quarries have no continuation; their extent is very confined, and proportionate to the height of the mountains which furnish them with the matter of their growth. The tuffa every day receiving lapidific juices, those small cylindrical columns, between which intervals are left, close at last, and the whole becomes one compact body, but never acquires the hardness of stone, and is what Agricola terms Marga tofocea fistulosa. In this tuffa are generally found impressions of leaves, trees, and plants, like those which grow in the environs: terrestrial shells also are often met with, but never any of the marine kind. The tuffa is certainly therefore a new matter, which must be ranked with stalactites, incrustations, &c. all these new matters are kinds of spurious stones, formed at the expence of the rest, but which never arrive at true petrification.
Crystal, precious stones, and all those which have a regular figure, even small flints formed by concentrical beds, whether found in perpendicular cavities of rocks, or elsewhere, are only exudations of large flints, or concrete juices of the like matters, and are therefore spurious stones, and real stalactites of flint or rock.
Shells are never found either in rock, granate, or free-stone, although they are often met with in vitrifiable sand, from which these matters derive their origin; this seems to prove that sand cannot unite to form free-stone or rock but when it is pure, and that if it is mixed with shells or substances of other kinds, which are heterogeneous to it, its union is prevented. I have observed the little pebbles which are often found in beds of sand mixed with shells, but never found any shell therein: these pebbles are real concretions of free-stone formed in the sand in the places where it is not mixed with heterogeneous matters which oppose the formation of larger masses.
We have before observed, that at Amsterdam, which is a very low country, sea shells were found at 100 feet below the earth, and at Marly-la-Ville, six miles from Paris, at 75 feet; we likewise meet with the same at the bottom of mines, and in banks of rocks, beneath a height of stone 50, 100, 200, and 1000 feet thick, as is apparent in the Alps and Pyrennees, where, in the lower beds, shells and other marine productions are constantly found. But to proceed in order, we find shells on the mountains of Spain, France, and England; in all the marble quarries of Flanders, in the mountains of Gueldres, in all hills around Paris, Burgundy, and Champagne; in one word, in every place where the basis of the soil is not free-stone or tuffa; and in most of these places there are more shells than other matters in the substance of the stones. By shells, I mean not only the wrecks of shell-fish, but those of crustaceous animals, the bristles of sea hedge-hogs, and all productions of the sea insects, as coral, madrepores, astroites, &c. We may easily be convinced by inspection, that in most calculable stones and marble, there is so great a quantity of these marine productions that they appear to surpass the matter which unites them.
But let us proceed; we meet with these marine productions even on the tops of the highest mountains; for example, on Mount Cenis, in the mountains of Genes, in the Apennines, and in most of the stone and marble quarries in Italy; also in the stones of the most ancient edifices of the Romans; in the mountains of Tirol; in the centre of Italy, on the summits of Mount Paterne, near Bologna; in the hills of Calabria; in many parts of Germany and Hungary, and generally in all the high parts of Europe27.
In Asia and Africa, travellers have remarked them in several parts; for example, on the mountains of Castravan, above Barut, there is a bed of white stone as thin as slate, each leaf of which contains a great number and diversity of fishes; they lie for the most part very flat and compressed, as does the fossil fearn-plants, but they are notwithstanding so well preserved, that the smallest traces of the fins, scales, and all the parts which distinguish each kind of fish, are perfectly visible. So likewise we find many sea muscles, and petrified shells between Suez and Cairo, and on all the hills and eminences of Barbary; the greatest part are conformable to the kinds at present caught in the Red Sea28. In Europe, we meet with petrified fish in Sweden and Germany, and in the quarry of Oningen, &c.
The long chain of mountains, says Bourguet, which extends from Portugal to the most eastern parts of China, the mountains of Africa and America, and the vallies of Europe, all inclose stones filled with shell-fish, and from hence, he says, we may conclude the same of all the other parts of the world unknown to us.
The islands in Europe, Asia, and America, where men have had occasion to dig, whether in mountains or plains, furnish examples of fossil shells, which evince that they have that in common with the bordering continents.
Here then is sufficient facts to prove that sea shells, petrified fish, and other marine productions are to be found in almost every place we are disposed to seek them.
"It is certain, says an English author (Tancred Robinson), that there have been sea-shells dispersed on the earth by armies, and the inhabitants of towns and villages, and that Loubere relates in his Voyage to Siam, that the monkies of the Cape of Good Hope, continually amuse themselves with carrying shells from the sea shores to the tops of the mountains; but that cannot resolve the question, why these shells are dispersed over all the earth, and even in the interior parts of mountains, where they are deposited in beds like those in the bottom of the sea."
On reading an Italian letter on the changes happened to the terrestrial globe, printed at Paris in the year 1746, I was surprised to find these sentiments of Loubere exactly corresponded. Petrified fish, according to this writer, are only fish rejected from the Roman tables, because they were not esteemed wholesome; and with respect to fossil-shells, he says the pilgrims of Syria brought, during the times of the Crusades, those of the Levant Sea, into France, Italy, and other Christian states; why has he not added that it was the monkies who transported the shells to the tops of these mountains, which were never inhabited by men? This would not have spoiled but rendered his explanation still more probable.
