278 TRANSACTIONS OF THE NORTHERN 



the older ages, than in the most recent periods. On the contrary, the 

 best evidence of long periods of repose relate to the Lawrentian age — 

 the very oldest section of rocks known to man; while evidence of the 

 most extensive oscillations relate to periods most recent. 



We have evidence of extensive continental oscillations even as re- 

 cent as the post-pliocene. All the highest mountain ranges have had 

 their principal elevation since the miocene or middle tertiary ; and a 

 large portion of the area of our present continents have been redeemed 

 from the ocean since the miocene period. At that period Europe was 

 but an archipelago of islands ; much of Asia and Africa were beneath 

 the oceans; the Gulf of Mexico extended up to the mouth of the Ohio, 

 and the whole Salt Lake basin was an inland sea. During the post-ter- 

 tiary or post-pliocene, Great Britain was twice elevated, so as to form 

 a part of the continent, and again sunk down so as to form a few small 

 islands ; and Scandinavia has been twice elevated and covered with 

 glaciers, and, we may add, if the present upward movement of Scandi- 

 navia continues, Norway and Sweden will be again covered with gla- 

 ciers. 



In view of such momentous oscillations within the most recent ge- 

 ological epochs, what have we to justify the notion of present stability, 

 except that we do not see it move? In short, the popular notion that 

 many entertain, that former ages were scenes of gigantic revolutions, 

 and that the earth's crust has now arrived at a state of comparative 

 rest, is not sustained by any geological evidence. 



The Great Western Plains, and Rocky Mountain region has, at the 

 present time, an elevation of from eight thousand to thirteen thousand 

 feet above the level of the sea. It is cold and arid, presenting little 

 encouragement to agriculture. But we have only to go back to the 

 miocene or middle tertiary, when this region had but a slight elevation 

 above the sea. It then enjoyed a mild climate, with abundant rain 

 falls, and was clothed with a rich luxuriance of sub-tropical trees and 

 plants. It then contained many extensive lakes, the former bounderies 

 of which are now traced by geologists. Prof. Hayden, in his geological 

 reports, states that one of these former lakes extended over much of the 

 plains east of the mountains, having an extent of over one hundred thou- 

 sand square miles. These bodies of water existed for a long duration of 

 time. According to Prof. Hayden, the accumulation in the bottom of 

 one of these lakes has a thickness of several thousand feet. 



But, as the centuries rolled on, the gradual elevation of the Rocky 

 Mountain region was in progress, — rain falls grew less, — those great 

 lakes began to diminish ; growing shallow first nearest the axis of eleva- 

 tion, and finally disappeared. Streams and fountains failed. The cli- 

 mate was changing — the sub-tropical trees and plants worked their way 

 to a more southern latitude, while a northern flora was gradually taking 

 their place. 



Thus we see how the elevation of the Rocky Mountain region has 

 transformed a land of former fertility into nearly an arid waste. In a 



