256 Geology and Botany of Northern Pacific Railroad. 



Cretaceous is deposited unconforrnably upon these, rising to the 

 height of but a few hundred feet above the sea. North of the 

 California line, the rocks forming the mountains, as has been 

 mentioned, are almost entirely eruptive ; and it is evident that 

 this has been the theatre of more violent volcanic notion ,than 

 any other part of the continent known to us. Most of the erup- 

 tions took place in Tertiaiy times, as we know from the inter- 

 calation of the trap overflows with the Tertiary lake-sediments, 

 many of which are store-houses of vegetable and animal fossils ; 

 but they have continued down to the present day. 



Many years ago, when connected with Western Government 

 Surveys, I followed these mountains from the California line 

 to the Columbia, and at several points crossed lava streams 

 which had flowed down the east flank of the Cascades, and 

 were as fresh and ragged as the modern lava streams of Vesuvius. 

 Not a particle of vegetation had attached itself to them, and it 

 is certain that not a hundred years have passed since some of 

 them were flowing. 



Ancient Glaciers of the Cascade Mountains. 



As has been stated, the Rocky Mountains, from New Mexico 

 to British Columbia, abound in evidences of ancient glaciation. 

 This is also true of the Uinta Mountains, the Wasatch, the Si- 

 erra Nevada and the Cascade Mountains. 



In the group of five snowy peaks, called in Oregon the Three 

 Sisters — because only three are visible from the Willamette Val- 

 ley — miniature glaciers were found by our party in 1855 at the 

 heads of McKenzie's Fork, and of one of the tributaries of the Des 

 Chutes ; and on Mt. Rainier a dozen or more have been described, 

 some many miles in length. But all the glaciers and snow-fields 

 now existing on the Cascade Mountains are utterly insignificant 

 compared with those of the glacial period. Then every gorge 

 was filled with snow and ice, the broader and more irregular 

 summits were covered with glaciers, and these descended several 

 thousand feet below the present line of perpetual snow. Now 

 we find, oyer miles square, the rock-surfaces planed smooth or 

 grooved like a plowed field, and every projecting crest of volcanic 

 rock, rough and ragged as it was, is rounded over and worn into 



