in the direction of the movement of the glacier rather than 
circular. Such thought, however, is only consistent with the 
presumption that the holes were made just where the water 
first fell upon the rock surface below. Far more reasonable is 
it to suppose that the holes were formed somewhat distant from 
this place, where the masses of rocks borne by the waters 
found a lodging in some depression and there by rotation 
worked out the potholes. The ice might move on and the 
waters descend through the moulin far from where they first 
fell, yet continue their flow in the same direction as at first and 
go on with the work of rotating the contents of the hole through 
a whole season. In such саве there could be, of course, no 
reason to expect the elongation." In explanation of potholes 
in close proximity to others and yet seemingly independent, as 
in the case of the Well, Mr. Bouvé says: ** Observation upon 
Alpine glaciers shows that as a crevasse is carried forward by 
the general movement of the ice it closes. Subsequently а new 
one is formed just where in relation to the land at the margin 
of the glacier the former one existed : and the waters again 
descend upon the rock surface near where they before fell, but 
not often, probably, in exaetly the same place; and thus pot- 
holes аге formed contiguous to each other and yet far enough 
distant to make it evident that they were not produced by the 
same flow of water." This is undoubtedly a true explanation 
of many glacial potholes : and its weakest point, as applied to 
most of the potholes of Cohasset is that it requires the water 
to flow up over instead of around the prominent ledges. 
Mr. Upham has suggested a different explanation. He 
says': ‘ The time of the excavation of these glacial potholes 
was probably the early part of the epoch of glaciation, when the 
ice-sheet was being formed upon the land by snow-fall. | Upon 
any hilly country the ice must have attained an average depth 
somewhat exceeding the altitude of the hills above the adjoin- 
ing lowlands before any general motion of the ice-sheet could 
Proc. В, 8. N. H., XXIV, 226-228. 
