122 MAN AND THE GLACIAL PERIOD. 



Cordilleran Glacier moved to a distance of six hundred 

 miles, extending to the Columbia Eiver, in the eastern 

 part of the State of Washington. 



From this centre, also, the ice descended to the sea- 

 level upon the west, and filled all the channels between 

 Vancouver's Island and the mainland, as well as those in 

 the Alexander Archipelago of Alaska. South of Van- 

 couver's Island a glacier pushed out through the straits of 

 Juan de Fuca to an unknown distance. All the islands 

 in Puget Sound are composed of glacial debris, resem- 

 bling in every respect the terminal moraines which have 

 been described as constituting many of the islands south 

 of the New England coast. The ice-movement in Puget 

 Sound, however, was probably northward, resulting from 

 glaciers which are now represented by their diminutive 

 descendants on the flanks of Mount Eainier. 



South of the Columbia Eiver the country was never 

 completely enveloped by the ice, but glaciers extended far 

 down in the valleys from all the lofty mountain-peaks. In 

 Idaho there are glacial signs from the summit of the Eocky 

 Mountains down to the westward of Lake Pend d'Oreille. 

 In the Yellowstone Park there are clear indications that 

 the whole area was enveloped in glacial ice. An immense 

 boulder of granite, resting upon volcanic deposits, may be 

 found a little west of Inspiration Point, on the Yellow- 

 stone Canon. Abundant evidences of glacial action are 

 also visible down the Yellowstone Eiver to the vicinity of 

 Livingston, showing that that valley must have been 

 filled with glacial ice to a depth of sixteen hundred feet. 

 To the west the glaciers from the Yellowstone Park ex- 

 tended to the border of Idaho, where a clearly marked 

 terminal moraine is to be found in the Tyghee Pass, lead- 

 ing over from the western fork of the Madison Eiver into 

 Lewis Fork of the Snake Eiver. South of Yellowstone 

 Park the Teton Mountains were an important centre for 

 the dispersion of local glaciers, but they did not descend 



