211 The American Geolqgist April, 1896 
that large volumes of drift may become englacial. It seems 
to me that this lias not been satisfactorily done as yet, and, 
as previously stated, the chief purpose of this paper is, if po>- 
eible, to reenforce the englacial theory at this point. 
The sedentary ice-sheet, as we have seen, holds in its grasp 
a large part of the surface detritus; and if, as I believe, the 
initial shearing plane is normally or usually at the lower limit 
of frost, a considerable bod} 7 of detritus, mostly of a fine or 
impalpable character (preglacial residuary soil, etc.), is en- 
glacial from the beginning of movement of the ice-sheet. 
When a sedentary ice-sheet is overridden by a piedmont gla- 
cier, and still more when a sedentary ice-sheet is overridden 
by the reiidvance of an earlier ice-sheet, the conditions must 
be favorable for the transfer of drift from the base of the ear- 
lier sheet to a somewhat elevated position in the composite 
sheet which results from the overriding. We may suppose 
that the overriding sheet will carry with it not only its own 
englacial drift, but will drag along, also, a part of its ground 
moraine or subglacial drift. This complex process will be 
repeated with each marked recession and reiidvance of the 
ice-sheet. 
It is altogether probable that each important recession of 
the ice-sheet, and not alone the final recession, was character- 
ized by numerous glacial rivers and lakes and an extensive 
development of modified drift in the well known forms of 
kames, eskers, deltas with abrupt northern margins, etc. It 
is obvious that such eminently loose and porous deposits 
would be completely permeated by and form an essential part 
of the succeeding sedentary ice-sheet. Thus material which 
may have slowly become englacial through the movement of 
an earlier ice-sheet is englacial from the beginning of the 
succeeding sheet. Or, if the later ice should move over these 
deposits, their forms and structures are very favorable to 
their being absorbed by the ice through shearing and flexing. 
Some of the illustrations accompanying Prof. ( 'hamberlin's 
valuable description of the Greenland glaciers* are well cal- 
culated to dispel any doubts that may exist in the minds of 
geologists as to the power of a glacier to absorb detritus by 
*Journal of Geology, in, 478, figs. 28-30. Bull. Geol. Soc. Amer., vi, 
203-214, plates 5-9. 
