RECESSIONAL ICE BORDERS IN BERKSHIRE, MASS. 331 



Besides (i) the moraines just mentioned, which are purely ice- 

 laid sediments, there are (2) kames, eskers, and the like, which 

 were made by the joint action of the ice and running water, and 

 which may generally be relied upon as good supplementary evi- 

 dence ; and (3) eroded river channels along the border of the 

 ice, outwash gravel fans, valley gravel trains, deltas, etc. 



Excepting for the small isolated kames which occur in spo- 

 radic fashion, kames, and especially kame clusters, are essentially 

 ice-border phenomena and are substantially equivalent to mar- 

 ginal morainic deposits. They nearly always occur at or very 

 near the margin of the ice and are very commonly associated 

 with moraines. 



Eskers are not quite so closely related to the ice-front, and 

 yet they are generally valuable aids ; for, although they may 

 extend for miles back, they nearly always take on a character- 

 istic modification of development where they emerge from the 

 ice. At such places they often take the form of a small kame 

 cluster or delta, or sometimes an outwash fan. When an esker 

 persists during several recessional halts, it generally shows one 

 or another of these modifications at each place where the ice- 

 front halted, although its ridge may be typically developed in 

 the intervals. A good example of this sort may be seen in the 

 great esker which runs south from North Adams to Berkshire. 



Deposits of the third class often show the place of the ice- 

 front in situations where there are no contiguous recognizable 

 morainic deposits. In the Berkshires especially this class of 

 evidence has been invaluable. Eroded river beds along the 

 border of the ice are traceable for long distances only where the 

 ice-front rested against a long unbroken mountain flank, as of 

 the Green mountain range or of Hoosac mountain. But there 

 are many places where shorter fragments of river beds are well 

 developed. The streams that made them were not large, as a 

 rule, but they are often very clearly cut in situations where their 

 occurrence would be altogether impossible without the immediate 

 presence of the ice-front to serve as one of the retaining banks. 

 These fragments often occur on hillsides and steep valley slopes, 

 and in other situations where the morainic deposits are absent or 



