240 TEE ICE AGE IN NORTH AMERICA. 



ders about four hundred feet wide, running continuously for 

 nine miles southeast. These bowlders are composed of a 

 chloritic schist, whose only outcrop is at Fry's Hill, on the 

 summit of the Lebanon range. West of the ridge there are 

 none of these bowlders, but east of the knob the train is con- 

 tinuous. Near the knob the size of the bowlders is larger 

 than at a distance from it. Indeed, the size gradually dimin- 

 ishes as the distance increases. The bowlders are distributed 

 equally over the valleys intervening and over the flanks and 

 summits of the ridges crossed. Besides the main continuous 

 train of bowlders there are three others more or less continu- 

 ous for a part of the way, and originating near the same 

 knob. The diameter of the bowlders varies from thirty feet 

 near their origin, to an average of two feet in Stockbridge, 

 nine miles away. In the vicinity are other bowlders from a 

 ledge whose outcrop was from four hundred to eight hun- 

 dred feet lower than the hills upon which they are now 

 resting. 



Sir Charles Lyeil's explanation of these remarkable trains 

 of bowlders was that they were deposited when the region 

 was depressed, so that oceanic currents carried icebergs over 

 the summits of the intervening range, dropping their burdens 

 along on the way. But it is surprising that the burdens of 

 the icebergs should have been deposited so regularly, and still 

 more surprising that icebergs should have raised bowlders 

 and deposited them on surfaces eight hundred feet higher 

 than the ledges from which they were torn. This is one of 

 those numerous cases where the glacial hypothesis easily 

 explains all the facts, and where it is difficult to see how 

 any other hypothesis can do so. 



The only really peculiar thing about these celebrated trains 

 of bowlders is that in their case the peak from which they 

 are derived is isolated so that their origin can be readily 

 traced. The prevailing rocks of this region are of such a 

 nature that large bowlders could not readily be formed from 

 them, whereas over most of the glaciated region the bowl- 

 ders are so abundant and from such a varietv of localities 



