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America ; and all,* from their magnitude, fitted to excite our wonder, 

 when we compare the diminutive size of the present races of animals 

 which inhabit that country. The animal remains found by Mr. 

 Darwin comprise, besides the Toxodon, which extraordinary animal 

 was as large as a hippopotamus, — (2, 3, 4, 5, 6.) the Megatherium, 

 and four or five other large Edentata; — (7.) an immense Mastodon; 

 — (8.) the Horse ; — (9.) an animal larger than a horse, and of very 

 singular character, of which a fragment of the head has been found ; 

 — -(10, 11, 12.) parts of Rodents, one of considerable size; — (13.) a 

 Llama, or Guanaco, fully as large as the Camel. 



But I should very ill convey my impression of the great value 

 of the researches of Mr. Darwin, by any enumeration of special points 

 of geology or palaeontology on which they have thrown light. Look- 

 ing at the general mass of his results, the account of which he has 

 been kind enough to place in my hands, I cannot help considering 

 his voyage round the world as one of the most important events for 

 geology which has occurred for many years. We may think our- 

 selves fortunate that Capt. Fitz Roy, who conducted the expedition, 

 was led, by his enlightened zeal for science, to take out a naturalist 

 with him. And we have further reason to rejoice that this lot fell to 

 a gentleman like Mr. Darwin, who possessed the genuine spirit and 

 zeal, as well* as knowledge of a naturalist; who had pursued the 

 studies which fitted him for this employment, under the friendly 

 guidance of Dr, Grant at Edinburgh, anvi Professor Henslow and 

 Professor Sedgwick at Cambridge ; and whose powers of reason 

 and application had been braced and disciplined by the other stu- 

 dies of the University of which the latter two gentlemen are such 

 distinguished ornaments. But some of the principal of these re- 

 sults may be most conveniently mentioned, when we pass from 

 mere descriptive geology, to that other division of the subject which 

 I have termed Geological Dynamics. And this I now proceed to do. 



GEOLOGICAL DYNAMICS. 



This term is intended to express generally the science, so far as 

 we can frame a science, of the causes of change by which geological 

 phsenomena have been produced. Without here speaking of any 

 classification of such changes, I may observe that the gradual eleva- 



