RECESSIONAL ICE BORDERS IN BERKSHIRE, MASS. 333 



It is about a mile broad, has a beautifully undulating surface, the 

 higher swells reaching an altitude of sixty feet above the sur- 

 rounding plain. Clay is a large factor in its composition, and it 

 originally carried a great number of bowlders on its surface. It 

 is built out across an open part of the Housatonic valley and 

 was made by an ice-tongue which came from the north out of 

 the Hoosic valley. The fact that this tongue deployed upon an 

 open plain caused it to expand as it advanced, and no doubt 

 gave its moraine the character described rather than that of the 

 next class of deposits, which is much more common in the Berk- 

 shires. There are moraines of this type, but not so well formed, 

 west of Hoosick Falls, N. Y., and there is a small fragment of 

 similar character three-fourths of a mile north of Ashley Falls. 

 '2. Terminal moraines of ice-tongues. — This class of moraines is 

 the best developed and the most common type in the Berkshires, 

 but it has both advantages and disadvantages as a means of 

 tracing the ice-borders. It is always fragmentary and limited 

 in extent, being confined in its best developments to the terminal 

 parts of sharply pointed tongues in relatively deep and narrow 

 valleys. On the other hand, excepting the first class, it is the 

 most easily and most certainly recognizable form of moraine. 

 These deposits are as a rule much coarser in composition than 

 either of the other three classes. Clay is usually a relatively 

 small constituent, and knob-and-basin topography is the common 

 form of expression. In many respects they resemble kames in 

 the forms they take, and many of them might well be mistaken 

 for such if their composition and the circumstances of their 

 occurrence were left out of account. They nearly always con- 

 tain a large percentage of gravel, and in this, too, they remotely 

 resemble kames. But as a rule they contain some clay and a 

 very large proportion of the coarser sediments, sometimes being 

 composed mainly of cobbles and bowlders, with only a filling of 

 gravel and sandy clay. Not infrequently small bodies of strati- 

 fied sand and gravel occur in them. They may be distinguished 

 from kames, however, by the fact that their best development 

 occurs in narrow valleys where there was free drainage from the 

 ice, while typical kames occur where there was more or less local 



