30 MAN AND THE GLACIAL PERIOD. 



away, a mute witness of the impressive and complicated 

 forces which have been so long in operation for its pro- 

 duction. 



In other places I have witnessed the formation of a 

 long ridge of gravel by the gradual falling in of the roof 

 of a tunnel which had been occupied by a subglacial 

 stream, and over which there was deposited a great amount 

 of morainic material. As the roof gave way, this was 

 constantly falling to the bottom, where, being exempt 

 from further erosive agencies, it must remain as a gravel 

 ridge or kame. 



In other places, still, there were vast masses of ice 

 covering many acres, and buried beneath a great depth of 

 morainic material which had been swept down upon it 

 while joined to the main glacier. In the retreat of the 

 ice, however, these masses had become isolated, and the 

 sand, gravel, and boulders were sliding down the wasting 

 sides and forming long ridges of debris along the bottom, 

 which, upon the final melting of the ice, will be left as a 

 complicated network of ridges and knolls of gravel, en- 

 closing an equally complicated nest of kettle-holes. 



Beyond Cross Sound the Pacific coast is bounded for 

 several hundred miles by the magnificent semicircle of 

 mountains known as the St. Elias Alps, with Mount Cril- 

 lon at the south, having an elevation of nearly sixteen 

 thousand feet, and St. Elias in the centre, rising to a 

 greater height. Everywhere along this coast, as far as the 

 Alaskan Peninsula, vast glaciers come down from the 

 mountain-sides, and in many cases their precipitous fronts 

 form the shore-line for many miles at a time. Icy Bay, 

 just to the south of Mount St, Elias, is fitly named, on 

 account of the extent of the glaciers emptying into it and 

 the number of icebergs cumbering its waters. 



In the summer of 1890 a party, under the lead of Mr. 

 I. C. Eussell, of the United States Geological Survey, 

 made an unsuccessful attempt to scale the heights of 



