DRAINAGE OF THE GLACIAL PERIOD. 337 



by the wash from the mountains on either side. This dam 

 separated the basin from the Port Neuf river which debouches 

 upon the Snake river plain at Pocatello. Evidently when the 

 opening was once made the whole body of water from the 

 upper 375 feet of Lake Bonneville poured down this little 

 valley in torrents which baffle all our descriptive powers. 

 Evidence of its torrential action are visible all along the 

 valley and especially at Pocatello where an immense bowlder 

 bed was deposited. (See figures on pages 615 and 703.) 



Note to the Fourth Edition. — Since the following chapter upon 

 "Karnes" was written, a partially successful effort has been made to 

 distinguish between kames and eskers; but the distinction is not so 

 well defined as to make it necessary to rewrite the chapter. Accord- 

 ing to Professor Chamberlin (see GeiMe's "Great Ice Age," third 

 edition, p. 7-46), eskers denote the long gravel ridges which conform in 

 general to the direction of the ice movement, while "kames take on 

 the form of bunchy aggregations of knolls and irregular ridges, and 

 have a tendency to arrange themselves in belts parallel to the margin 

 of the ice." But "it is not to be understood that any sharp line of 

 distinction can be drawn between the two types. They are connected 

 by intermediate forms which are difficult to place in either class. The 

 kames, as well as the eskers. are regarded as products of glacial drain- 

 age." 



