354 THE ICE AGE IN NORTE AMERICA. 



greater part of the Glacial period. Of this as a reality there 

 is abundant evidence. All the streams which rise within 

 the glaciated region and flow southward were compelled to 

 carry away not only the annual precipitation, but, during 

 the closing stages of the period, the waters of the accumu- 

 lated precipitation of many thousands of years. If the an- 

 nual spring freshets of these streams are oftentimes terrific, 

 what must have been the spring freshets in the Glacial period 

 itself! 



Into the Mississippi also were poured the surplus waters 

 which now flow down the St. Lawrence, and into Hudson 

 Bay. Lake Erie emptied its waters through the Wabash 

 River, and Lake Michigan down the Illinois ; while the 

 great region drained by the Red and other rivers of Mani- 

 toba and British Columbia had their outlet through Lake 

 Traverse and Big Stone Lake, into the Minnesota, and 

 thence into the lower Mississippi. The terraces of the gla- 

 ciated region are the direct results of these glacial floods, 

 and can be studied on every stream within its boundary. 



Besides the glacial terraces of our present streams, we 

 have, in the so-called " kame systems," still further evidence 

 of the existence of temporary lines of drainage determined 

 by ice-barriers. New England is gridironed by a system of 

 gravel ridges deposited by glacial streams which were, to a 

 great extent, independent of the minor features in the pres- 

 ent topography. In these and in the terminal moraines we 

 study the skeleton of the continental ice-sheet as intelli- 

 gently as the anatomist can study the skeleton of a dis- 

 sected animal. 



