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force continued unimpaired even subsequently to the formation of some tertiary deposits, those geologists who contend it is now in the wane must reason from a very limited number of facts indeed. - Both Mr. Poulett Scrope* and Dr. Daubenyť in their recent publications agree in considering that the effects produced at present by earthquakes and volcanos are at least analogous in kind, if inferior in degree, to those that have resulted from similar agents at remote æras. More than 170 volcanos are at present in activity on the land, even if separate orifices at a short distance from one another be reckoned as one volcano ; and there is reason to believe that there are at least as many, and probably a much greater number, beneath the sea—the power of which latter in throwing up islands and altering the bed of the sea is well known.
The chain of extinct volcanos described by the above mentioned authors in Auvergne, the latest of which became extinct before the period of any historical records; the streams of lava, which can be traced from their craters to the choked up vallies, and to the ancient courses of rivers thereby diverted into new channels; these and many more phenomena raise the strongest presumption in favour of the great antiquity of some parts of the European continent. When we consider the deltas of large rivers, the strata at the bottom of freshwater lakes in Germany, Italy, and England, but, above all, the recent deposits at the bottom of the great American lakes Superior and Huron, inclosing shells of the very species now inhabiting those lakes and exposed to view in consequence of the subsidence of the water occasioned by the partial destruction of their barriers, we can affirm with certainty that modern freshwater deposits, of no inconsiderable thickness, far exceed in area the ancient freshwater formations, at present described. As to the scale on which submarine strata are now formed, we remain, of course, in comparative ignorance, but it is certainly more considerable than has been supposed by many. Whether the coral reefs of the East Indian archipelago are built up from an unfathomable depth, as Flinders imagined, or are based on submarine volcanos, as Kotzebue and more modern writers suppose, we are at least certain, from the manner in which these zoophytes increase, and from the necessary accumulation of their broken fragments, that those aggregations of calcareous matter cannot be of slight depth, while we know that their superficial extent is immense. Captain King, in his late survey of Australia, sailed along a continued
* Considerations on Volcanos, by G. Poulett Scrope, Esq. London. 1825.
+ See p. 2. Description of active and extinct Volcanos, by Charles Daubeny, M. D. London. 1826.
#Letters to Professor Jameson, on the Volcanus of Auvergne, by Charles Daubeny, M.D.F.R.S. Dr. Bigsby in the Journal of Science, &c. No. 37. pp. 262, 263. KK 4
line of coral reef for 700 miles, interrupted only by a few intervals not exceeding 30 miles. These reefs stretch from the north-east coast of Australia towards New Guinea, and very far exceed in length any chain of secondary mountains in Europe. It is unnecessary to remind the geologist, how close a resemblance masses of such zoophytes intermixed with calcareous sand and the exuviæ of testacea so abundant in tropical seas, must bear to the greater part of the ancient oolitic formations. A calcareous concreted sand-rock unquestionably of modern formation has been found to exist in Australia throughout a space of no less than 25 degrees of latitude, and an equal extent of longitude, on the southern, west, and north-west coasts. We might adduce many more examples from the Mediterranean, and other seas, but we shall content ourselves with stating, in conclusion, that the stone of Guadaloupe containing the human skeletons is, in parts, as compact as the greater proportion of our secondary rocks. This description of rock is very common in the West Indian Archipelago, and increases rapidly; it forms the 'gained land,' which has extended the plain of Cayes in St. Domingo, and there the remains of pottery and other human implements have been found at the depth of 20 feet.
* There are still, it may be said, some conglomerate rocks in Europe and in America, such, for instance, as are remarkably exhibited both in the old and new red sandstone formations, that evince a continued and destructive action over
great extent of the globe, unparalleled by existing causes. That the sudden elevation or subsidence of land might be attended with such tastrophes will, however, hardly be denied. Earthquakes and volcanos are, for the most part, characterized by brief periods of intense activity, interrupted by irregular intervals of quiescence.t Of the duration of these intervals we must be, at present, altogether ignorant, for centuries of complete tranquillity have interyened between recorded eruptions of volcanos accompanied with violent shocks of earthquakes.--But we cannot allow ourselves to speculate farther on these topics, and return to our zoological observations.
Of birds an extremely limited number have hitherto been dis. covered in a fossil state, and their scarcity forms a striking contrast to the abundance of other kinds of vertebrated animals. In the gypsum of Paris, however, before mentioned, several well defined species have been found and described by M. Cuvier. They were coeval with the Palæotherium and its contemporaries, and were different, like them, from any species now living; yet, with Cuv. Discours sur les Rev. &c.
+ Scrope, on Volcanos, p. 9.
respect to the general laws of co-existence and structure, and all that relates to the nature of their organs and their essential functions,' they were the same as those of our own time.'*
But in oviparous quadrupeds, remarkable alike for their magnitude and organization, nature has, in ancient epochs, teemed throughout these latitudes with a prolific power not exerted at present even between the tropics. These quadrupeds occur in strata of far more ancient date than the viviparous class. They make their first appearance in England in the lias, where many skeletons are procured in so perfect a state that the most exact knowledge has been obtained of their structure. . In the volume before us are two excellent papers, by Mr. Conybeare, on the osteological characters of the fossil genera Ichthyosaurus and Plesiosaurus, both first discovered and determined in this country. • The Ichthyosaurus is an animal entirely sui generis ; possessing, bowever, sufficient analogies with the Saurian order to justify our referring it to that great natural division :-it holds an intermediate place between the crocodile and lacertæ.' Like the Cetacea-it was exclusively an inhabitant of the sea ; its eyes were of an enormous size, its neck short, its tail extremely long, its paddles broad and fat, and its whole frame admirably adapted for passing with rapidity through the water. Mr. Conybeare has ascertained four distinct species: one of these, I. communis, sometimes exceeds twenty feet in length; and I. platyodon was yet more gigantic.
The Plesiosaurus was still more extraordinary. Of this genus five species are ascertained. An almost entire skeleton of one of these--P. dolichodeirus, found in lias at Lyme Regis in Dorsetshire, and now in the possession of the Duke of Buckingham, is figured in this volume. This specimen does not exceed eight or nine feet in length, but the same species sometimes attained the length of twenty feet. It was distinguished from all known oviparous and viviparous quadrupeds, by a thin slender neck, equalling or exceeding the body in length, and composed of above thirty vertebræ.
* This great increase,' observes Mr. Conybeare,' of the number of joints in the neck is the more remarkable from the rigour with which nature appears in most cases to have enforced the law of a very limited number. In all quadrupedal animals, in all the mammalia, (excepting only the tridactyl sloths, which have nine,) the series is exactly seven ; and so strict is this rule, that even the short and stiff neck of the whale, and the long and flexible neck of the cameleopard are formed out of the same elementary number; the vertebræ in the former instance being extremely thin and anchylosed together, and in the latter great! ated. Re:
* Cuv. Oss. Foss. vol. iii. pp. 13
all those of Cuckfield, are terrestrial, lacustrine or fluviatile. We have not sufficient information concerning the bones, teeth, and palates of the various fishes and sharks to decide that any two of them agree in species. This remark applies with still greater force to the remains of cetacea and birds. No Didelphis has yet been found in the Tilgate beds, no Iguanodon at Stonesfield. That the bones of gigantic dimensions procured at. Cuckfield belong strictly to the same genus as the Megalosaurus.of. Stonesfield, we have little doubt, although the bones of the skeleton bitherto found in actual apposition at either place are so few, that to determine this point, much less to decide on their specific identity, is impossible. The same may be said of the Plesiosaurus and Crocodile. · Although the tortoises are numerous in both localities, none have yet been shown to be of the same species. The correspondence, in short, of the remains at Stonestield and Tilgate Forest, imbedded in strata totally dissimilar in mineralogical characters, is what we might expect to find between the same formations and the deltas of the Nile, Ganges, and all large rivers of the present day in hot climates.
We have only space to allude briefly to some of the geological papers in this volume. They contain a great mass of new information, and we cannot but express our regret that the Geological Society, possessing so many zealous members, and engaged in promoting a science so fertile in new discoveries, should have permitted a lapse of two years to intervene between the completion of the volume we have been reviewing, and a new part; published whilst we are concluding this Article. There are two papers by Mr. Colebrooke on the valley of the Sutluj river, in the Himalaya mountains, and on the north-eastern border of Bengal, and another by Mr. Fraser on the country between Delhi and Bombay, which, when considered together, are sufficient to establish a remarkable resemblance in the leading geological features of the vast continent of India to that of Europe and North America. The primary rocks in Central India and in the Himalaya mountains are identical in mineralogical character with those of the Alps, and, in fact, of all primary ranges in the world. The striking analogy of the fossils from the north-east of Bengal to those of the formations above the chalk in England, is extremely curious, and quite consistent with the conclusions already deduced from the organic remains procured in the strata near Madras, and deposited with specimens from various parts of India in the museum of the Geological Society. The identity of the başalts and amygdaloids, and other varieties of trap brought by Mr. Fraser from India, with those found in similar situations in England, is no less interesting; and lastly, the coal formation,
consisting of micaceous sandstone, bituminous shale and coal, on the banks of the Tista and Subuk rivers, which descend from the Bhotan mountains, cannot fail to recal to the mind of the geologist the ancient coal formations of Europe and North America,
The joint paper on the south-western coal district of England, by Dr. Buckland and Mr. Conybeare, deserves attention no less for the variety than the importance of its contents. It establishes the relations of some of the most remarkable British rocks, and furnishes us with an accurate description of the physical geography of a large district. It may also be regarded as a statistical document of the first authority, containing numerous detailed sections of collieries and a determination of the limits of the coal fields of Bristol, the Forest of Dean, and several of minor extent, by which their present productive powers and future resources may be estimated; lastly, it supplies data, founded on multiplied observations, which may direct the search of the miner to new discoveries, and often prevent a fruitless expenditure of capital in insuccessful trials. The Bristol coal district, illustrated by the beautiful map and sections accompanying this memoir, may be pointed out to the student as full of instruction, for a great variety of formations are here comprized within a small space; and, while a knowledge of their regular order of superposition may be easily obtained, instructive examples occur of the occasional absence of different members of the series and of the leading features of disturbance exhibited on so immense a scale in high mountain chains. We regard this country also as the more entitled to the student's preference, because trap rocks, so abundant in the coal fields of Scotland and the north of England, are here entirely wanting, at least in every formation from the old red sandstone to the oolite inclusive. Geologists have in general commenced their investigations in countries where the derangement of the strata was greatest, and all the phenomena attending them the most complicated. They have studied the exceptions before the rule; and when to this we add disregard to the present operations of nature, whether with reference to aqueous deposits or volcanic products, we cannot be surprized that the theories of the earlier professors of this science, even when founded exclusively on facts and observations, were contradictory; and that the generalizations of Werner and Hutton, though bearing impressed upon them the decided marks of genius, have required considerable modifications.
Two great series of rocks occupy the south-western coal district. In the first, comprizing the lowest and most ancient formations, (the greywacke transition limestone, old red sandstone, mountaiv limestone and coal measures,) the strata are highly inL L 3