TRANSPORTATION OF DEBRIS BY ICEBERGS Sr 
dence of the same kind. Specifically the fact that both the Tully 
limestone erratics and the local sandstone fragment in the iceberg 
deposit show conspicuous wear indicates that in the short distance 
such fragments traveled, and presumably under the thin, waning 
front of the glacier, there was nevertheless accomplished a very 
notable amount of erosion of these fragments, and it may be inferred 
that the bedrock surface over which the fragments were dragged 
was subjected to a like amount of reduction. This suggests that 
even the relatively thin and inactive frontal lobes of waning glaciers 
are quite effective erosive agents. 
Summary.—Iceberg deposits of bowlders, found in fine-grained 
lake clay, occur in pockets, as if derived from single bergs. If that 
is the case the material brought by each berg is of considerable 
mass. The bowlders are in very high percentage of foreign, 
resistant rocks, and a very large proportion of the specimens shows 
signs of mechanical wear of glacial nature. Hence it is concluded 
that the iceberg deposits examined were from the bottom ice of the 
glacier. Locally derived material found in the deposits shows 
similar wear. Since these iceberg deposits must have been the 
very last deposits made by the last retreat of the ice, it is argued that 
the notable grinding of the local material indicates that even the 
thinned lobes of a waning glacier had considerable erosive effect- 
iveness. 
