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periods and at different intervals of time to destroy the animate productions of nature, modern industry has afforded ample proof; but the labours of geologists have also shown how much of the history of extinct races may yet be rescued from oblivion. It is now twenty years since Playfair observed, “that the land has been raised by expansive forces acting from below, and there is reason to think, that continents have alternately ascended, and descended, within a period comparatively of no great extent.' When the Huttonians first advanced these doctrines, no geologists disputed that there existed proofs of former changes, in the relative level of land and sea, but Playfair's hypothesis appeared extravagant to many, and those were deemed • fearless of paradox who,' as Mr. Greenough expressed it,* .attributed to the waves constancy, mobility to the land. Yet the Huttonians were conducted to these conclusions by the observation of a class of phenomena altogether distinct from what may now be considered as furnishing the most decisive evidence in favour of them. Playfair had examined with attention the dislocations and disturbances of rocks, but the alternation of a great series of marine and freshwater formations was not then established,—nay, has only been generally admitted since all the facts from which it is inferred have been rigorously examined by persons possessing a competent knowledge of organic remains, and who have compared recent with ancient freshwater deposits.

It may not be superfluous to mention a few of the most striking of these facts. The strata associated with the Coal contain in many countries indications of a fresh-water origin; and the vegetable remains preserved in them prove the existence of dry land at the period of their deposition. The bituminous copper slate of Thuringia is of an older date than the magnesian limestone of the English series; it contains reptiles of the Saurian family, closely resembling the great monster that now lives in fresh water in the torrid zone,t and the unknown fish that abound in the same slate are regarded by Cuvier as related to freshwater genera. Strata of freshwater origin, and of considerable thickness, exist between the chalk and the oolitic series in the south-eastern districts of England. The chalk is exclusively a marine deposit; and, from its great extent in Europe, and the absence of vegetable matter, sand and transported materials, is considered to have been formed at the bottom of a deep and tranquil sea. But above the chalk, both in this island and on the continent, alternations of marine and freshwater strata occur. The lowest of these are

* A Crit. Exam. of the First Principles of Geology, 191. + Cuv. sur les Rev. p. 299.

See Mem. by Dr. Fitton, Ann. of Phil. Nov. 1814.

filled with vegetable inatter, and in some localities in France with freshwater shells. Upon this group of strata a formation rich in a great variety of marine remains is placed, both here and in France : above that formation, again, is the freshwater deposit already referred to as including terrestrial quadrupeds; this is again covered in its turn by marine beds; and incumbent upon them in like manner another series of freshwater strata is found.

To explain such phenomena by supposing that the ocean has alternately risen and fallen, in other words, that its level has been, both frequently and permanently, changed over the whole globe, is an hypothesis unsupported by facts. But of changes in the level of the land we have ample testimony, and some are particus larly recorded in the volume before us,* where an account is given of the late memorable earthquake that visited Chili in 1822, and continued to be felt there till near the end of 1823. The shocks of this earthquake were experienced throughout a space of 1200 miles from Ñ. to S., and at Valparaiso it appeared, on the morning of the 20th, (Nov. 1822,) that the whole line of coast from N. to S., to the distance of above 100 miles, had been raised above. its former level;' an old wreck of a ship, which before could not be approached, was now accessible from the land. The alteration of levelt at Valparaiso was about three feet, and some rocks were thus newly exposed, on which the fishermen collected the scallop, which was not known to exist there before the earthquake. At Quintero the elevation was about four feet.

• When I went to examine the coast,' says Mrs. Graham,' although it was high-water, I found the ancient bed of the sea laid bare and dry, with beds of oysters, muscles, and other shells adhering to the rocks on wbich they grew, the fish being all dead, and exhaling most offensive effluvia. I found good reason to believe that the coast had been raised by earthquakes at former periods in a similar manner, several ancient lines of beach, consisting of shingle mixed with shells, extending in a parallel direction to the shore to the height of fifty feet above the sea. The country bas in former years been visited by earthquakes, the last of any consequence having been 93 years ago.' I

Part of the coast thus elevated is stated to consist of granite, in which great parallel fissures were caused by the earthquake. Besides the excellent account of these phenomena given by Mrs. Graham, the observations of several other persons were published in the Journal of the Royal Institution, where it is stated, that • the whole country, from the foot of the Andes to far out at sea, was raised, the greatest rise being at the distance of about two

* Ibid.

* Page 413.

+ Page 415. $ Jour. Roy. Inst. for 1884. vol. xvii. pp. 40. 45.

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our readers a concise view of the principal data on which the prevailing opinions of naturalists in regard to it are founded.

Remains of large herbivorous quadrupeds occur in the superficial gravel of Europe and North America, referable to genera now contined to warmer climates. Their number does not diminish as we proceed northwards, but, on the contrary, the greatest abundance has been found in Siberia, where the vegetation is now so scanty and buried for so long a time under the spow of a polar winter, that it is impossible to conceive how herds of elephants could ever have existed there, had the climate been always so severe as it is at present. Various oviparous quadrupeds, tortoises, turtles, crocodiles, and those gigantic Saurian animals, which engaged our attention in an earlier part of this essay, are distributed in profusion throughout the strata of every part of Europe, some even in the most recent formations above the chalk, and others in different parts of the series, down to the lias and the copper-slate of Thuringia inclusive. Nothing analogous to these classes of large reptiles exists at present in temperate latitudes.

Univalve shells are said to predominate in number over bivalves throughout the secondary strata in Europe, as at present in tro pical seas.* To the occurrence of large chambered univalve shells, and the conclusions to which they point, we need not again refer. Corals and other zoophytes are found at present to increase in size, in variety of species, and rapidity of growth, as we approach the equator. They form large reefs in intertropical seas, where their comminuted fragments constitute a considerable portion of the beach, and are remarkable for their tendency to consolidate, with other loose materials, into rock. Such a state of things must be supposed to have existed when the oolitic series and many other strata in Europe were deposited. But as we ascend towards the superior and more recent formations, which contain genera of shells more analogous to those now inhabiting our seas, fossil zoophytes become much rarer and inferior in size. : • The above inferences are derived from so extensive a collection of facts, that the number of exceptions must be regarded as singularly small, and most of these are merely founded on analogy like the evidence on the other side. Remains of Cetaceous animals, for example, of a genus now exclusively tropical, have been discovered in a limestone in France, the calcaire grossière, with a species of another Cetaceous genus now peculiar to the frozen zone.. A more remarkable exception occurs in the discovery of

* Defrance, Tab. des Corps Org. Foss. 51. 125. + Cuv. Discours sur les Rev. p. 313.

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cient geographical information. He describes the steppe extending between the Black Sea and the Caspian as

lying at an extremely low and generally uniform levele it is marked (he proceeds) by an extreme want of fresh water, and is covered with sand and recent shells, such us are now found in the neighbouring seas.

The lakes and pools which it contains are mostly salt, and the scanty vegetation of the steppe consists of such plants only as are found with us on the sea coast, or which are of a like nature. The rock under the superficial sand is a hard clay, sometimes left bare.'* Mr. Strangways has traced on the map accompanying his memoir the supposed former communication of the Black Sea with the Caspian, and of the latter with the salt lake, Aral,

according to which there must formerly have been either two inland seas separated by land in the neighbourhood of the Bosphorus, or the Mediterranean must have extended to the interior of Asia as far as the low steppe continues ; and in that case its eastern shore would have been the high land which, in the steppe of the Kirghis, connects the Altay with the Himalaya mountains. Many considerable islands and peninsulas would have been thus formed; such as the Crimea, Kharizm, the Beshtan, &c., for the bed of a, strait is said to be traced across the isthmus of Perecop, including the steppe of the Dnieper on the vorth, and a part of that of the Crimea on the south ; the lake Aral would have been joined by narrow seas with the Caspian on the north-west, and perhaps also on the south-west, &c.' We must be satisfied with referring our readers to the author's own remarks on the illustration of several ancient geographical accounts and traditions afforded by these geological facts.

No one can reflect on the above statements without being tempted to inquire whether the causes now in action are, as Dr. Buckland has supposed, the last expiring efforts of those mighty disturbing forces which once operated;+ or whether, as Hutton thought, they would still be sufficient in a long succession of ages to reproduce analogous results. The opinion repeated by M. Cuvier in his last publication, I that it is in vain to search in the forces now acting on the surface of the earth for causes sufficient to produce revolutions and catastrophes of which the traces are exhibited in its envelope,’ is entitled without doubt to the more respect, as it seems to have been adopted by many in these later times, when additional facts have been so industriously accumulated. The total amount of change that has fallen under the observation of mankind in the course of 3,000 years is, however, so small, that the final decision of this question may certainly be regarded as incalculably remote, and indeed we can be content, for our part, to waive the speedier Page 37.

+ Vindicia Geologice, p. 5.
+ Cuv. Discours sur les Rev. &c. p. 11.
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was far more intense than is now experienced even between the tropics; and however astonishing this inference may seem, it can scarcely be rejected until some ground is shown for distrusting all evidence derived from analogy on these subjects. That we by no means comprehend all the laws that regulate the geographical distribution of living plants over the globe must be confessed. That there are some causes hitherto undiscovered, capable, in co-operation with temperature, of promoting or retarding the development of certain forms and characters of vegetation, is more than probable; but that temperature is at present the most powerful of all, is unquestionable; and that it was so when the Plants of the coal were in being we must presume, until reasons are adduced for believing that the system of nature has, in this respect, been entirely changed.

As to the manner in which so surprizing a revolution in the temperature of the globe has been effected, no conjecture deserving much consideration has yet been made known; and if à satisfactory explanation of so difficult a problem is ever obtained, we shall probably be indebted to astronomy for it. Geology can only account for local fluctuations of climate in the same latitudes, by furnishing us with evidence almost conclusive, that, during the deposition of stratified rocks, changes in the distribution of land and sea were frequent and considerable. In consequence of these changes the relative extent of superficial land and water may often have differed greatly. Continents or open seas may have alternately existed at the poles or at the equator. The land, according to its varying form, would necessarily determine in particular directions warm currents from tropical towards arctic seas, or cold currents bearing floating ice from arctic towards tropical latitudes. But these causes, though far too important to be kept out of view whenever this question is considered, are essentially partial in their operation and limited in degree; whereas the phenomena indicate most signal and remarkable alteration in climate, and that co-extensive with every part of the northern hemisphere hitherto examined in America, Europe, and Asia:

Some modern authors conceive that a comparison of the fossils of Bengal, the Carnatic and other equatorial countries, with those of Europe and North America, warrants the conclusion that the former temperature of the earth was more uniform as well as more elevated than the present; and they endeavour to explain this circumstance by supposing that climate was formerly independent, in a great degree, of solar heat, deriving warmth from the interior of the earth itself, which, since the original oxydation of its metallic nucleus, has been (say they) in a state of gradual refrigeration. We should not have ventured to ainuse our readers

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