Bouv£.] 
180 
[Dec. 17, 
to Hingham Harbor, which then was open to the spread of its wa- 
ters bnt a few hundred feet from where the river takes an eastward 
course as mentioned. 
It is due to Prof. W. O. Crosby to state that he suggested the 
probability of this to the writer, and that subsequent examination 
by both revealed to us that an extensive kame deposit here had 
caused the river, which had flowed for some distance directly north 
to make the detour mentioned. 
Kettle-Holes. 
Intimately connected with the kames are depressions in the sur- 
face, sometimes of considerable depth, which have received this 
name. Their origin, formerly a puzzle to students of glacial phe- 
nomena is no longer so, as nature has been detected in the very 
act of their formation. From observations of Dr. G. F. Wright 
upon the glaciers of Alaska, he found that when a considerable 
surface of melting ice-sheet had been covered over to any depth 
with earth material, rocks, pebbles and sand, the ice thus prevented 
from melting beneath remained intact, whilst all more exposed over 
the field sunk away and finally disappeared. The result of this 
would be to leave a great mass, sometimes of large area, to settle 
as the glacier retreated from it, with enormous weight upon the 
subsoil below. Here it would remain until melted, and it might 
require the heat of many summers to effect its entire dissolution, 
protected as it would be from the sun’s rays by its earthy cover- 
ing. As, however, the melting progressed, this covering matter 
would necessarily slide down around its margin, producing ridges 
and hillocks of material, the forms of which would be more or less 
modified by the running water from the ice as it dissolved away. 
With the accumulated quantity of matter thus deposited, the rest- 
ing-place of the ice mass would be much below the surrounding 
surface. After knowing the results of Dr. Wright’s investigations, 
it may be confidently stated that there can be no longer reasonable 
doubt concerning the origin of these depressions. 
The Passing Away of the Ice-sheet. 
Some suggestions respecting the kame ridges, the kame hills, 
and the kettle-lioles may well be presented in remarks upon the 
passing away of the great ice-sheet that had for ages covered the 
land. The reality of the ice spread over the whole North, where 
previously for millions of years a tropical climate had prevailed ; 
