122 Prof. J. W. Spencer—Ice Action in the North. 
the motion is much more rapid than the flow of land-ice, which is 
three feet a day or less, and corresponds to the experimental move- 
ment—shown by Herr Pfaff,—under which conditions, as seen in 
Norway, included stones commonly adhere by friction to the 
subjacent rocks, and cause the lower surfaces of the ice to be grooved. 
Eixtraordinarily rapid movement has been seen at Jacobshavn glacier 
in Greenland, where Prof. A. Helland! found that the velocity 
reached 40-60 feet a day. In Alaska, Lieut. Schwatka? and Prof. 
G. F. Wright * observed a movement of 40-70 feet a day. In these 
cases the glaciers are moving into the sea, and a new element of 
partial flotation or sliding, which does not belong to the glaciers on 
land, is here introduced. The great velocity of these glaciers is far 
beyond any known ability of ice to flow asa plastic body. Con- 
sequently one is led to conclude that under partial flotation stones 
may be held firmly as graving tools by glaciers. 
8. The appeal to the former magnitude of ice-masses as accom- 
plishing different results from those seen at present seems to be 
begging the question, for the action under a greater thickness would 
differ from that under a lesser, in amount rather than in kind, for 
increased pressure upon the ice—raising the temperature—increases 
its plasticity, as the general mass is not below freezing-point. Con- 
sequently it seems improbable that stones should be held firmly under 
the changed condition, for in addition to the increased plasticity, the 
friction between the stones in the ice, and the rock, is also increased 
by the greater weight of ice. 
9. Over the vast area of action, the work of floating or sea-ice in 
some form, is enormous. 
On the northern side of Hudson Straits Dr. John Rae, who had 
very extensive Arctic experiences, found that snow, drifting over 
precipices into the sea, resulted in the formation of bergs 100 feet 
thick (filled with loose rock-débris of the coast), having the form of 
the shore where they were produced. Most of the bergs break loose 
and drift away to melt or become stranded elsewhere. 
10. Greely describes the great momentum with which floebergs 
come together, and by their meeting, the ice is crushed and forced 
up into ridges 50 to 60 feet high. 
11. One cannot carefully read the results of the last British Arctic 
Expedition of 1875-76, under Sir George Nares, without being 
impressed with the erosive power of drifting ice. Floebergs are 
pushed upon a shelving sea-bottom, until the ice has risen Z20—60 
feet, after their first stranding, in perhaps only 48—72 feet of water, 
although of gigantic weight. As the grounded floebergs are forced 
up the shelving sea-bottom,. ridges of earth and stones are pushed up 
in front of them. Floebergs which have toppled over, thus showing 
their original bottoms, and also the pushed-up coast-ice, are found 
to be grooved and to contain angular stones with their exposed 
1 See Q.J.G.S. 1877. 
2 N.Y. Times Alaska Expedition, 1886. 
3’ The Muir Glacier, Amer. Journ. Sci. 1887. 
# Canadian Journ, Toronto, 1859, 
