WISCONSIN TILL 551 



can not be seen positively to merge with the dnuulin till, there is a possi- 

 bility that one of them is a third till, and that the clays extend under 

 the drumlins in some cases. This supposition is improbable for the 

 reason that where the till underlying the clay has been seen it can not be 

 distinguished in character from that of the drumlins, and also because 

 it is found in locations where it appears to slope upward and merge with 

 the drumlin surface underlying the Wisconsin till. However this may 

 be, a till Avhich is in every respect like the drumlin till and apparently 

 identical with it underlies these clays, and no evidence has been found 

 that it is different from the drumlin till. 



Another possible explanation for the discrepancy in observations is that 

 there may be drumlins of both Montauk and Wisconsin ages, but in 

 Massachusetts all drumlins are so similar in characteristics that none of 

 them are believed to be Wisconsin. At a number of points on the Maine 

 coast many miles farther northeast than the farthest known drumlin of 

 the type found in Massachusetts and New Hampshire, a few low lenticular 

 hills of till have been seen which may belong to a different series from 

 those in Massachusetts and New Hampshire, The best examples of this 

 eastern type form small islands in Penobscot and Bluehill bays. 



Distinction from leach deposits. — Wisconsin till is distinguished from 

 beach gravel by the fact that it seldom shows signs of having been assorted 

 by water, that large boulders are found in it far from their source, that 

 these are occasionally striated, and that the material is found in many 

 localities far inland and in topographic situations where beaches could 

 not be formed. In several places true ancient beach deposits have been 

 seen, but they are all on exposed hillsides and the deposit in each case 

 corresponds with a slight bench. The materials believed to be Wisconsin 

 till show no such distribution or topography, but are irregularly distrib- 

 uted. 



Distinction from iceberg-di-opped material. — In cases where a material 

 is irregularly distributed and so frequently contains large boulders as the 

 Wisconsin till, it is pertinent to inquire whether it may not be iceberg- 

 dropped in origin. It is true that in some places the resemblence to 

 material that might have been dropped from icebergs is striking. In 

 most exposures, however, only a small part of the deposit consists of 

 boulders, and the mass forms a fairly regular layer a few feet in thick- 

 ness with a rather even upper surface, while iceberg-dropped material 

 would be expected to be more irregular in thickness and distribution. 

 Moreover, in the case of Augusta exposures, the folding and erosion are 

 evidence against any mode of formation except deposition from moving 

 ice. 



