246 THE FOREST LANDS OF FINLAND. 
Both theories attribute them to the action of ice. In one 
of these, advanced and expounded in a volume. entitled 
Frost and Fire, by Mr J. F. Campbell, they are attri- 
buted to the friction of icebergs and icefloes, drifting from 
the north on ocean currents. In the other, advanced, 
maintained, and illustrated by Agassiz, Ramsay, Lyell, 
Chambers, Jamieson, and Geikie, they are attributed to 
the grating action of glaciers, or land ice, formed where 
they are seen, or at a somewhat higher level, and con- 
tinuously descending in a state of flux to a lower level. 
By some of the geologists whom I have cited it is held 
that in what is known as the glacial period Scotland must 
have been covered with one wide-spread sheet of ice and 
snow of great thickness, as at the present day is Northern 
Greenland, where there may be seen an interminable glacier, 
extending league upon league, broken only by some black 
hill top or mountain peak that rises as an island above the 
sea of ice. But there this vast sheet is ever, even while 
being replenished by fresh falls of snow, slowly and 
persistently flowing, or rather creeping, down to the sea, 
covering the face of the country, filling up the valleys, 
mounting over the hills, and pressing with constant resist- 
less force upon all the rocks over which it advances; and 
blocks of stone, either loosened from the mountain by 
frost, or torn off by the moving glacier, are jammed in in 
the rear, and pressed along the rocky bed or sides of the 
valley ; and the stones, mud, gravel, and sand thus borne 
along act like files scratching and scoring the hardest 
rocks, and being themselves scratched by the same process. 
As it is now in North Greenland so must it have been 
during the glacial period in Scotland. There we find the 
rounded, filed down projections on the mountain top and 
on the mountain sides, and the parallel striae. So must it 
have been at the same period, and on to a later time, in 
Norway; and thus many numerous phenomena presented 
by the mountains and the rocks there be satisfactorily 
accounted for; and to the same operation may be attri- 
