418 CONSISTENCY OF GEOLOGY WITH SACRED HISTORY. 



their nodules and veins of flint, have more the character of a chemiv 

 cal production, than of a mere mechanical deposit ; and may perhaps 

 owe their origin to precipitation from thermal waters. The shells and 

 crustaceous coverings of the echini are invariably changed into calca- 

 reous spar ; and in many instances the terebratulcB are twisted and 

 contorted in every direction, without the shells exhibiting a single 

 fracture ; changes which probably resulted from the influence of a 

 high temperature under considerable pressure. 



With the exception of the pentacriniis, the teeth of fishes resem- 

 bling those of the shark, the teeth of crocodiles, and perhaps a few 

 shells,* the organic remains of the chalk differ entirely from all known 

 existing species, as well as from the fossils of other formations. The 

 thickness of the chalk, which is estimated at upwards of 12G0 feet, 

 and the immense variety and numbers of its organic remains, evince 

 that the agents which produced it were in full activity through a long 

 period of time.f Although we have no satisfactory evidence to deter- 

 mine whether the chalk were deposited over the entire surface of the 

 Wealden (as seems most probable,) or whether the latter were under- 

 going elevation during the deposition of the chalk, and were but par- 

 tially covered by the cretaceous strata, yet there can be no doubt that 

 the chalk originally very much exceeded its present limits. It is true 

 that gravel, and partially rolled flints, occur but rarely on the Weal- 

 den, the diluvial covering of the latter chiefly consisting of its own de- 

 bris ; yet this fact may have resulted from the action of the sea during, 

 the elevation of the strata, or many other causes, and cannot be admit- 

 ted as aflbrding conclusive evidence that the Wealden was never whol- 

 ly covered by the chalk. Our limits will not allow us to examine this 

 interesting question in all its bearings, which will be fully elucidated 

 in the 3d volume of Mr. Lyell's " Principles of Geology," now in the 

 press ; and we proceed to the consideration of the next geological 

 era — that in which the older tertiary strata were deposited. 



The epochs we have already noticed are marked by immense muta- 

 tions in the relative situation of the land and sea ; yet these changes 

 appear to have been eflbcted in such a manner as to have occasioned 

 comparatively but little derangement in the strata, and to have been 

 succeeded by periods of repose of long duration. In the tertiary era,, 

 on the contrary, it is manifest that the disturbing forces were in fre- 

 quent and violent action, and produced elevations and subsidences, 

 and enormous dislocations and fissures, throughout the whole mass of 

 the strata of the south-east of England. In the anticlinal axis of the 

 Forest ridge, from whence the strata diverge to the south-east in Sus- 

 sex and the north-west in Kent, we have evidence of a force having 

 acted from beneath, in a direction from east to west, by which the 

 Wealden beds have been elevated above the chalk formation, and the 



* Even these few exceptions are very equivocal, and probably the species will 

 hereafter prove to be distinct from their supposed analogues. 



t The fossils of the chalk of Sussex are enumerated in the Catalogue in the Ap- 

 pendix to this work. In the list of the organic remains of the cretaceous strata of 

 Europe, given by M. De la Beche, there are, of Reptiles, 6 or 8 ; Fishes, 10 or 12 ; 

 Crustacea, 15; Mollusca, 225; Conchifera, 285; Annulata, 110; Radiariaj 90j 

 Vegetable remains, 20 species, 16 of which are marine. 



