36 BULLETIN OF THE 



ever, the nearest approach to tliem being a slight rounding of some of 

 the sharper corners and edges. It seems evident that these boulders 

 have suffered none of that extreme abrasion which would have been 

 caused by friction against the bed-rocks. 



It is probable, then, that the boulders of the trains were removed 

 from their original bed by the lower surface of the ice-sheet, and became 

 imbedded in the mass of the ice instead of being dragged along beneath 

 it. This supposition is in harmony with the observed sharpness of the 

 knob called Fry-'s Hill, the origin of the principal train, since boulders 

 torn from its upper part would be at least 100 feet above the lower sur- 

 face of the ice-sheet along the neighboring parts of the crest, and the ice, 

 closing together again as soon as it had passed the sharp knob, would 

 hold many of them firmly without allowing them to work down to the 

 rocks below. 



Two great deviations from the normal course may be observed in the 

 boulder trains, especially in the principal one. If that part of the ice 

 containing the bouldere had met with no deflecting force, it would have 

 preserved a rectilinear path in a S. 50° E. direction. The maxima of 

 deviation from the normal course are on the western spurs of the Rich- 

 mond Range, and on the western slope of the Western Branch of the 

 Lenox Range, and they show by their positions relative to Perry's Peak 

 and Lenox Mountain that these mountain masses were the obstacles 

 which temporarily turned aside the boulder trains from their normal 

 course. » 



The second, third, and minor trains exhibit gaps, caused probably by 

 the temporary fiiilure of the ice to get hold of any of the rock material ; 

 the tough schist resisted successfully for a time the efforts of the ice to 

 tear it from its bed ; then a mass was obliged to yield to the prolonged 

 strain, and, becoming loosened, the resulting fragments were borne away. 

 The rock left behind, being still firmly fixed in its place, would in its 

 turn resist for a time, thus causing another gap in the train, till in time 

 another mass would be obliged to yield to the rending action of the ice, 

 and so the process would go on. 



Tlie sharper the knob the narrower the train to which it gave origin. 

 This statement is Avell illustrated by the fact that the southeasterly 

 pai'ts of the second and third trains, which were given off at first when 

 the knobs were sharp, are quite narrow and distinct, while the more 

 northwesterly parts of the same trains, which were given off later, when 

 the kiu)b8 had become somewhat rounded, are very much broader. 



A diminution in the size of the boulders towards the southeast has 



