Conclusions. 
365 
where nearly free from carbonates. To the present writer it 
seems that this question has not received the thorough investi¬ 
gation which its theoretical importance demands. There are 
other ways of accounting for the presence of these carbonates 
besides the one inplied above. But first of all the actual 
amount of such carbonates should be determined over a large 
area in till of all types and at various depths. 
If it be argued that the amount of till is too great to be ac¬ 
counted for in the way here suggested, i. e., by pre-glacial rock 
disintegration, it should be borne in mind that the region from 
which the ice moved is the oldest part of the world. Its rocks 
are quite susceptible to the forceb of decay, and it is simply 
impossible that they should not have yielded to those forces in 
all the millions of years since they were formed. Nor is it 
reasonable to suppose that all the results of decay were washed 
into the streams and carried to the sea to form the beds of 
Paleozoic and later rocks. It is incredible that there should 
not have been a residuum of decomposed rock comparable in 
most respects to that now found in the Archaean regions south 
of the glaciated area. But there is now no such residuum in the 
northern region, the rocks have been swept clean and the mater¬ 
ial carried southward by the great ice sheet. 
To this material was added whatever the ice could break-off 
or rasp off from the bed over which it flowed. I believe that 
this load of sub-glacial debris would be forced into depressions 
and, filling them up, protect them from the glacial wear, while the 
prominences would feel the full force of the glacial rasp. The 
effect would be, not to make rock basins, and so strengthen the 
relief, but by filling depressions and cutting down prominences 
to lessen relief. 
6. The undoubted great transporting power of ice has not 
been carefully discriminated from its eroding power. The huge 
blocks which it has transported are usually spoken of as hav¬ 
ing been torn from the rocky bed of the glacier by the same 
force that transported them. A ledge of rock weakened by 
weathering, fissured by crustal warpings and standing squarely 
in the way of a powerful ice sheet would probably fall an easy 
