Perry.] 100 [February 28, 
over, this elevation. Of course with such an obstruction! in the way 
of the ice-mass, there could readily, and, one may presume, there 
probably did occur a break in the ice, what is known in a mod- 
ern Alpine glacier as a moulin, or well, just above the summit of 
the hill. Now a glacial stream—a thing of constant occurrence in 
the present, as it undoubtedly was in the past—flowing on the sur- 
face of the wide spread field of ice from the north or the north-west, 
in consequence of the thawing of the superficial snows under the 
heat of the noon-day sun, and falling into the moulim, must have had 
precisely the effect of a cascade or mountain torrent.2 Indeed, it 
would be a torrent, or a cascade, according to varying circumstances, 
—a glacial, torrent or cascade,—and thus naturally produce the re- 
sults in question. The pot-holes connected with modern glaciers dif- 
‘fer creatly in form. Those of the Ice period, as one might expect, 
have a like diversity. Frequently they are round, or nearly so; 
sometimes they are more or less oval; while in many instances, they 
are oblong, perhaps having somewhat the appearance of one in the 
vicinity of New Haven, described by Professor Dana as “like a 
bread trough in shape.’ 
This explanation of the phenomena in the locality referred to, 
which was suggested years ago by what Professor Agassiz says of 
results, probably kindred in their character, produced by Alpine 
glaciers, may render the whole matter easy of comprehension and 
help to account, in an intelligible manner, for many similar occur- 
rences in different parts of the country. It should be remarked that 
such pot-holes were probably formed at various heights, in connec- 
tion with the surface streams of the overlying glacier. Of course, 
the most elevated could have been produced only during the Middle 
Glacial times, when the ice was probably of great thickness; those 
1 Jt is well known that, when existing glaciers meet with obstructions, there oc- 
cur in them breaks which are called moulins by the Swiss mountaineers; that, 
from the melting of the snows on the surface of the glaciers, many streams are 
formed; andthat these, flowing into the breaks, become cascades and torrents, 
which wear pot-holes in the underlying rock, in every respect similar to those re- 
quiring an explanation.—See Professor Agassiz’s Systéme Glaciaire. 
2 Professor Agassiz informs me that there is no end of the cascades upon the 
large glaciers of Switzerland. He says that all these cascades, from the super- | 
ficial rivulets upon the glaciers, falling into the moulins, remain stationary—just as 
eddies in a river—while the glaciers moves on. His explanation is: the ice breaks 
constantly, as it moves forward, and closes up again after passing the obstacle 
which causes the break. 
5 Paper cited, p. 62. 
