ANCIENT GLACIERS. 71 



Indeed, trains of boulders ought to appear almost 

 everywhere over the glaciated area; and so they do where 

 all the circumstances are favourable. But, readily to iden- 

 tify the train, requires that to furnish the boulders there 

 should be in the line of the ice-movement a projecting 

 mass of rock hard enough to offer considerable resistance 

 to the abrading agency of the ice and characteristic enough 

 in its composition to be readily recognised. Ship Rock, 

 in Peabody, Mass., weighing about eleven hundred tons, 

 and Mohegan Rock, in Montville, Conn., weighing about 

 ten thousand tons, have ordinarily been pointed to as 

 boulders illustrating the power of ice-action. Their glacial 

 character, however, has been challenged from the fact that 

 the variety of granite to which they belong occurs in the 

 neighbourhood, and indeed constitutes the bed-rock upon 

 which they rest.* Some would therefore consider them, 

 like some of which we have already spoken, to be boulders 

 which have originated through the disintegration of great 

 masses of rock, of which these were harder nuclei that 

 have longer resisted the ravages of the tooth of time. It 

 must be admitted that possibly this explanation is correct; 

 but it is scarcely probable that, in a region where there 

 are so many other evidences of glacial action, these boul- 

 ders could have remained immovable in presence of the 

 onward progress of the ice- current that certainly passed 

 over them. 



However, as already seen, we are not left to doubt as 

 to the movement of some boulders of great size. That 

 which now claims the reputation of being the largest in 

 New England is in Madison, N. H., and measures thirty 

 by forty by seventy-five feet. This can be traced to 

 ledges of Conway granite, about two miles away.f Many 

 boulders in the vicinity of New Haven, Conn., can be 



* Popular Science Monthly, vol. xxxvii, pp. 196-201. 



f See W. 0. Crosby's paper in Appalachia, vol. vi, pp. 59-70. 



