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Α Ρ Ρ Ε Ν DIX
MONTHLY REV I E W.
VOLUME the SIXTY-FOURTH.
A Ř T. 1. Lettres Physiques et Morales sur l'Hifoire de la Terre et de l'Hommit,
&c.-Letters Philosophical and Moral concerning the History of the Earth and of Man; addreiled to the Queen of Great Britain, by J. A. De Luc, Citizen of Geneva, Reader to her Majesty, F. R. S. Correspondent Member of the Royal Academies of Sciences at Paris and Montpellier, in Five Volumes &vo. Hague, 1780. il. 10 s. Sold in London by Elmfly, &c.
E .return with pleasure to this excellent work, though
we can only give our Readers an imperfect and general idea of the riches it contains. In a former account of its valuable contents, we followed the ingenious Author, in his analytical progress ihrough a multitude of phenomena, and observa-, tions founded on them, to the great revolution that produced the present state of our globe to-the fea's changing its bed and covering the ancient continents, after having previously covered
After having ascertained this important event by an exact analysis, M. De Luc enters into a synthetical examination of the results of this inquiry, and gives us the physical history of the earth from its primordial state to the revolution that occafioned its present aspect. In defcribing the changes which the furface of the earth has undergone, he fets out with this position, that when the sea covered our continents, it had a mountainous bottom, which neither the waters nor any known cause had formed, and which therefore our Author calls primordial. Some of these
• Vid. Appendix to the 6zd volume of our Review, p. 527.
mountains arose above its furface, and formed islands: these islands and the ancient continents were fruitful, and were peopled : the ancient sea, which covered the modern ones, had its tides, its currents and tempefts. These powers, acting upon the soft matters which are known to have formed the ancient bottom of the ocean when it covered our continents), produced accumulations of calcareous substances, more or less mixed, in process of time, with marine bodies. The rivers, in the mean while, carried to the sea scattered fragments of terrestrial vegetables and animals; the fea, itself, washed them off its coasts; and these materials, transported by its currents, became a fecondary soil or ground upon its primordial bottom. Our Author fhews, how fires kindled and elastic fluids (formed by the fermentation, which the waters, filtrated through these accumulated bodies, produced) made various openings in the bottom of the ocean, from whence proceeded torrents of liquefied substances and lava, which gave rise to the volcanic mountains, observable on the surface of our continent. The cavities, produced in the interior parts of the earth by the eruption of these liquefied substances, assumed the form and direction of galleries, and thus undermined the bottom of the sea to a considerable extent. (We abridge and refer the Reader to the work itself for the details and proofs of all this, which are abundant and fatisfactory.) These excavations, when large quantities of elastic fluids were engendered at once, produced earthquakes, which Thook even the mountains, and occafioned in them chinks or openings. These chinks were prevented from closing by the ruins that fell into them from the sides of the mountains, and, being afterwards filled with heterogeneous substances, in whose composition the sea-water and subterraneous fire may have concurred, exhibited veins, in which, since they have been dried, the filtration of the waters has produced a variety of changes, of which many are observable.
The bottom of the ancient sea (which covered our continents before the Deluge) had under it caverns, whose vaults, being thinned and impaired by the excavations made by subterraneous fires, were either pierced, or fell in from time to time. Hence the gradual finking of the sea beneath its level, from the en. trance of its water into the caverns, which diminished the influence of the tides on its undulations; while, from its bottom, being traversed by secondary elevations, considerable changes enfued in the direction of its currents, and consequently a great variety in the height, position, and nature of its accumulations. It is very remarkable, that the sea, after having made great acquifitions of calcareous matters in the first period of its operations, ceased almost every where to accumulate this kind of substances, and subdituted vitrescible matters in their place, long before it with
drew from our continents, and in a third period had scarce
any thing to transport from one place to another but marl, clay, and sand, the latter of which, more especially, it spread both on its primordial bottom, and also on the secondary ones formed by its own preceding deposits.
The continents, which existed in a state of population and fertility while the ancient sea covered ours, though they did not form a solid mass, but were, properly speaking, vaults, which covered immense caverns, maintained their elevation above the level of the fea by the strength of their pillars, which, being of primordial matter, were folid and stable. But the particular changes, which the fubterraneous fires produced in the bottom of the ancient sea, opened passages for its waters into the interior of the earth, and thus introduced them into some of the caverns, which were covered by the ancient continents. The fermentation, produced by this irruption, fhook the pillars of the primitive earth, which sinking into its caverns, the continents disappeared : their surface descending below the level of the sea, made room for the waters to spread themselves on every side ; but as the declivity was gentle, and the borders of the bason which emptied itself were unequally elevated, the inundation, though rapid, was only superficial, and neither put in motion, nor drew'after it, the sandy bottom, which ftill remains entire in our continents.-At the end of this first part of the great revolution, the sea covered all the globe, except the islands of its ancient bottom, which increased in number and magnitude, but continued still separate, until the weight of the water, added to that of the superior vaults, cruihed the inferior ones, and deepened more and more the new bed of the ocean; so that, at last, by a motion rapid though not violent, all the waters withdrew from their former bottom, and left our continents dry. The extinguished volcanos on our continents are a standing proof of the folidity of M. De Luc's system; as also the situation of the volcanos actually known, which are all in islands, or in places near the sea. As soon as our continents were delivered from the waters, the fermentations which they produced in combination with fire and other physical agents, cealed; these agents, having no more that weight of water to raise by which they fhook the vaults of the galleries, made some explosions indeed, which dispersed the ruins of the shattered ground, and covered fome parts of our continents with a discharge of primordial stones, but their efforts were exhausted for want of aliment, in galleries, whose vaults were pierced, instead of caverns, where there would have been opposition and materials to foment their activity. The old volcanos were therefore extinguished (and their numbers were prodigious, as we see by the late important publication of M. Faujas de St. Fond), and new volcanic erup.
tions arose in the new bed to which the waters withdrew. The Grecian, Sicilian, Indian, and Northern Islands may be al. ledged as illustrations of this history of the first of the two periods into which our Author divides that part of the duration of our globe, which is accessible to our inquiries by the phenomena it exhibits.
Having treated the ancient history of our globe, fo far down as the great revolution (or Deluge) that produced the continents we actually inhabit, our Author proceeds to its modern history, which takes in the period between that revolution and the present time. Here our ingenious investigator has still more ample succours and surer guides, as all the causes that began to operate upon our globe, after the formation of our continents, continue Itill their action and influence. By the view of these an estimate may be made both of their past and present effects, and this view will enable the fagacious inquirer to measure, with no small degree of precision and probability, the time that has elapsed fince these causes began to operate.--- Accordingly, our Author enters into this investigation. He obferves, that the two general sources, from whence the new earth (our present continents) received the germs of fertility and population, were the plants, feeds, and animals, that the sea, during the great revolution, carried off from the sinking continents, and which, driven by the winds and waves, were thrown upon the ancient islands (our present mountains), in proportion as they rose out of the departing ocean, and afterwards upon the borders of the new continents. These deposited materials of vegetation continually accumulated the turbification * of vegetables in low grounds of a fandy bottom the diminution of fertility on the high mountains from the accumulations of fnow and ice, which constantly increase (and would have already crusted over these mountains entirely, if the antiquity of our globe was so remote as fome philofophers pretend)-the wastes of the mountains and the talus formed by the mouidering parts of them that fall from time to time and the substances which the rivers carry in their current to the fea ;these are the five classes of phenomena which M. De Luc employs, ingeniously, to prove the recent origin of our continents, and to Thew that the present state of the earth's surface is not of a very ancient date. This is farther confirmed, as our Author obferves, by the history of mankind, whose destination it is to cultivate the earth and to study nature, and who, nevertheless, have hitherto made but small steps towards the accomplishment of these important purposes.
After having confidered the phenomena which afcertain the
* We have adopted from the French this term, which expresses the change of vegetables into a turfy earth. 22
great revolution above mentioned, M. De Luc examines those which characterise in a more particular manner the nature of that revolution, and shew, that it was effectuated by the pafsage of the sea from one part of the globe, which it had formerly covered, to another part, which it had not covered!'. The marine fossils, contained in the mountains, hills, and plains of our continents, and which characterise animals, of which some classes have not, as yet, been discovered in any fea, and others that have only been observed living in seas at a great distance, are employed by our Author to prove this parsage, as it has been already described. The remains of a great number of terrestrial vegetables and animals are found in our continents (inclosed in the substances which were accumulated by the sea when it formerly covered them), of which animals a very considerable number are different from all the classes of living animals known in our regions; while others belong to classes that only exist in the opposite hemisphere, and others again have not been, as yet, discovered living in any part of the globe.-All these circumstances are ingeniously brought to thew, that there existed populous and fertile continents during the period when ours were covered by the sea.
That fragments, skeletons, and remains of animals, which at present live only in the southern regions, should be found in the bowels of the earth in the northern parts of our hemisphere, is indeed a very singular phenomenon. M. De Buffon accounted for it by his whimsical hypothesis of the original fiery Auidity of our globe, and its gradual refrigeration, which produced the removal of several classes of animals towards the Equator, which had formerly inhabited the regions of the North. This system, which was a pretty entertainment for the beaux and belles of Paris, intoxicated some people from whom more wisdom might have been expected; and many readers were so amused to see the elephants and rhinocerosses galloping towards the Equinoctial; that the epochas of Nature * were almost universally applauded, and warmly defended. But they have had their day, like the elephants of the North, and are now contracting the influence of that refrigeration which their inventor attributes to our terrestrial globe. Our Author has not suffered them to cool gradually, or to die away of themselves : he has given them ą finishing, a deadly blow, from which it will be impossible for all the magic of M. De Buffon's pen to recover them. The Letters in which he examines M. Buffon's hypothesis, and M, Mairan's notion of a heat peculiar to the earth, on which this hypothesis is founded, are fingularly interesting and instructive; and thew in reality that M. De Luc is a master in the science
• See the Appendix to Vol. Ixi. of this Review,