346 THE ICE AGE IN NORTH AMERICA. 



terraces — being newer than the till and older than the ter- 

 races. 



On going over the ground in 1881 with Mr. Upham' s 

 notes in his hands, Professor Dana concluded that what Mr. 

 Upham had called kames were in reality a portion of the 

 regular terrace formation. In Professor Dana's view, the 

 reputed karnes are merely the coarser part of the terrace 

 material accumulated in excessive amount in the larger val- 

 ley wherever tributary streams brought into it their heavier 

 burdens from the higher land. On this theory, the height 

 of the floods in numerous localities must have been between 

 two hundred and three hundred feet above low water in the 

 river ; for in various places these deposits are at that height 

 above the river. But upon the supposition that they are 



Segregated veins 

 iuJower portion. 



375 ft, above sea. 



Fig. 106.— Section east from Ledyard Bridge, Hanover, New Hampshire, showing segre- 

 gated veins in the lower portion. Length, about seven hundred feet. Height of 

 kame above the river, one hundred and forty feet. (Upham.) 



kames, deposited when the ice itself formed barriers to keep 

 the streams in various abnormal positions, the glacial floods 

 would not need to be more than from one hundred to one 

 hundred and fifty feet in height, since that is all that is 

 required for the deposition of the highest river-silt which 

 occurs. 



It must be confessed that Professor Dana's estimates of 

 the size of the Connecticut Piver floods at that time are 

 somewhat startling, even with all the changes of level for 

 which he provides in his theory.* For, after reducing, by 

 reason of the Champlain depression, the gradient of the 

 stream during the close of the Ice period by one third, the 



* "American Journal of Science," vol. cxxiii, 1882, p. 198. 



