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glaciers, and then see if similar indications preserved upon the 
rocks of the Tertiary period, do not lead to the conclusion that 
they are the result of like causes. The snows which fall upon 
the mountains of Switzerland are pressed into masses of ice, 
and these, necessarily in obedience to the force of gravitation, 
have a tendency to move down their sloping sides. 
For a considerable period a discussion was carried on, not 
always in the true philosophical spirit, as to the physical state 
of the frozen mass of the moving glacier. One hypothesis 
regarding ice as a plastic material, moving by virtue of that 
plasticity, as pitch moves — the other supposing the ice to be 
melted by the enormous pressure to which it is subjected; but 
immediately recongealing, or as it is expressed, regelating into 
a homogeneous solid, and thus maintaining its onward motion. 
We need not here examine the delicate differences between 
those two views. Since we now know that solid iron, cold , may 
be pressed by a sufficient exercise of mechanical force through 
small orifices — flowing indeed as a fluid flows — there surely 
nan be no difficulty in conceiving how “the glacier’s cold 
resistless mass ” may be forced onward, day by day, by the enor- 
mous mechanical power which is ever pressing it in the rear. 
The writings of Agassiz, and of Professor James Forbes, have 
rendered familiar the fact that the moving glacier, by its enor- 
mous pressure, rounds off the asperities of the rocks, and covers 
their surfaces with striations. By a steady grinding process all 
the original angles are worn off, and the whole assumes a 
mammilated appearance ; the surfaces being polished, grooved 
and striated by the imprisoned stones and finer debris that lie 
between the solid mass, of the slowly progressing ice, and the 
rocky floor over which it passes. This moving frozen river of 
ice carries with it every thing that falls upon it, from the 
smaller debris, to the huge blocks of rock, which have been 
broken out of the mountains — roches moutonnees and blocs 
perches — and these are transported by it, to be left eventually, 
as the ice melts by advancing to a warmer region, to mark the 
course taken by the glacier. Such are the results of the known 
movements of glacial ice. When those frozen masses advance 
into the sea — as they do on the coasts of Greenland — they are 
gradually broken up into icebergs, which float far away towards 
the south, eventually melting under the influence of warmer 
waters, and dropping on the sea bottoms any boulders, or 
smaller masses of rock, which they may have borne from the 
land upon which they originated. 
These fragments of the disintegrated rocks are left as unmis- 
takable indications of the channels along which the glaciers 
moved, or of the regions over which the gliding ice of the land, 
or the floating iceberg of the sea, bore its weighty spoil. This 
