MUSEUM OF COMPARATIVE ZOOLOGY. 35 
It seems possible to arrive at a satisfactory explanation of the origin 
of the trains by first considering the principal train, which is, of all the 
four, the most complete, and the one which reveals most unmistakably 
its origin. Fry's Hill, evidently the point of origin of this train, has 
been referred to as a sharp knob, situated on the crest of the range, and 
composed chiefly of chloritic schist. To the north and south of this 
knob, however, exposures of chloritic schist are wanting, the rock being 
chloritic sandstone and mica schist. It seems tolerably plain, then, that 
it is partly to the sharpness of the knob, and partly to the narrowness 
of the limits to which the chloritic schist is confined, that the narrow 
distinct train owes its formation. 
The second train is, in all essential characters, like the principal train. 
Its direction in the Shaker Valley indicates that it originated upon a 
knoll situated on the crest of the range, half a mile S. S. W. from the 
origin of the principal train. It would be natural to expect to find that 
the train is continuous to this point, and that the knoll is composed, 
like Fry's Hill, of chloritic schist. On the contrary, it is composed of 
chloritic sandstone, and no chloritic schist boulders are to be found on 
its eastern slope. The explanation seems to be that the knoll once bore 
a mass of chloritic schist similar to that upon Fry’s Hill, though much 
less in amount, and that, though it continued for a time to give off 
boulder material, the supply of chloritic schist in that spot was finally 
exhausted, the fragments having been all torn from the knoll, and at 
length deposited in their present positions. 
In a similar manner the origin of the third and minor trains may be 
accounted for. 
In what particular manner were the boulders transported by the ice- 
sheet? They either rested on its upper surface, or were dragged along 
between its lower surface and the bed-rock, or were imbedded in the 
mass of the ice. 
The first of these suppositions cannot be sustained, since it presup- 
poses cliffs upon the Canaan and Lebanon Range which reached above 
the surface of the ice, whereas an ice-sheet which could move across val- 
leys six hundred feet deep, without being materially deflected from its 
course, must have covered the highest land in the region to the depth 
of many hundred feet. 
The second supposition is equally invalid, since, if these boulders had 
been dragged along under the ice, they would of necessity be much 
abraded, most of them showing smoothed surfaces, which would be likely 
to bear strie, None of these effects are to be found upon them, how- 
