On American Geological History. 403 



America lias thus the simplicity of a single evolved result. 

 Europe, on the contrary, is a world of complexities. It is but one 

 corner of the Oriental continent, — which includes Europe, Asia, 

 and Africa, — and while the ocean bounds it on the north and 

 and west, continental lands inclose it on the south and east. It 

 has ever been full of cross purposes. American strata often 

 stretch from the Atlantic west beyond the Mississippi ; and east 

 of the Rocky Mountains, it has but one proper mountain range 

 of later date than the Silurian. Europe is much broken up into 

 basins, and has mountains of all ages : even the Alps and Pyre- 

 nees are as recent as the Tertiary. 



This wide contrast accounts for the greater completeness or 

 generality of American revolutions, the more abrupt limits of 

 periods, and clearer exhibition of many geological principles. 



The geological structure of this country has been made known 

 through the combined researches of a large number of investi- 

 gators. The names of Mac lure, Silliman, Eaton, lead off the 

 roll ; Hitchcock, the Professors Rogers, the well-known Geol- 

 ogists of the New York Survey, also, Owen, Percival, 

 Morton, Conrad, Tuomey, and many others, have made laro-e 

 contributions to the accumulating results. Yet the system may 

 be said to have been mainly laid open by four sets of observers, 

 — Morton for the Cretaceous ; Conrad for the Tertiary ; the 

 Kew York Geologists for the Palaeozoic strata ; and the Pro- 

 fessors Rogers for the Carboniferous beds and the Appalachians. 

 The succession of Silurian and Devonian rocks in the State of 

 New York is the most complete in the country, and it was well 

 for the science that its rocks were so early studied, and with such 

 exactness of detail. The final display of the Palaeontology by 

 Mr. James Hall has given great precision to the facts, and the 

 system has thereby become a standard of comparison for the 

 whole country, and even for the world. 



This accomplished, the Carboniferous rocks were still to be 

 registered, and the grand problem of New England Geolooy 

 solved. The Professors Rogers, in the surveys of •Pennsylvania 

 and Virginia, followed out the succession of strata from the 

 Devonian through the Coal Period, and thus, in a general way, 

 completed the series. And more than this, they unravelled with 

 consummate skill the contortions among the Appalachian?, bring- 

 ing order out of confusion, and elucidating a principle of moun- 

 tain-making which is almost universal in its application. They 



