64 SEVENTH REPORT—1837. 
mammalian remains in the marine drift. No absolute junction of 
these gravels has yet been noticed, though they occur within a quarter 
of a mile of each other, at, as already stated, very different eleva- 
tions—the marine drift being highest, asa portion of the great deposit 
formed prior to the elevation which gave rise to the river or chain of 
lakes which formed the fluviatile drift. 
Mr. Strickland then stated the following as his own conclusions 
from the data he had collected or studied—namely, 
1st. That the great mass of erratic gravel which exists in England 
has been brought by a northerly current, at a time when all, or the 
chief part of England, was under the sea, and contains no terrestrial 
fossil remains. 
Qnd. That bones of terrestrial mammalia are only found in the 
deposits of ancient rivers or lakes, formed after England had been 
raised above the sea, and had nearly assumed its present form. 
Mr. Strickland concluded by suggesting to Geologists the necessity 
and importance of collecting data for solving the intricate question 
of the origin of gravel deposits, such as the varieties of rocks found 
in each deposit, the mode of its arrangement, the presence and kind 
of fossils contained in each, the elevation at which they are respect- 
hey found, and the relations they seem to have to the existing sur- 
ace. 
On the Mechanism of the Movement of Glaciers. By 
Rozsert Matrer, MR.LA. 
After briefly alluding to the peculiar appearances of glaciers, and 
their vast extent, equal in some cases to the area of a small English 
county, Mr. Mallet observed that, notwithstanding the labours of 
Merian, Hottinger, Simler, Scheuchzer, Griinen and Saussure, the 
forces which give rise to their motions, modify their forms, and lead to 
their increase or decrease, have been overlooked. To supply this 
defect fully would be beyond the limits ofa single paper, and Mr. Mallet 
therefore confined himself to the consideration of those forces which 
caused the descending. or precessional motion of glaciers, of the 
causes of the vast rifts or crevices which traverse them, and of the 
peculiar arrangement of the moraine or stony debris which covers large 
tracts of their icy surface. Hitherto writers (Saussure, Playfair, etc.) had 
ascribed their descent to the action partly of the weight of the glacier 
itself and partly of that of the vast masses of snow resting upon it, which 
together, had driven the glacier gradually forward, on the inclined 
plane upon which it rested ; and this explanation had been adopted and 
repeated by later writers, including Dr. Prout in his Bridgewater 
Treatise. This view Mr. Mallet considers inadequate to explain the 
progressive movement, sometimes as much as 25 feet in a year, since the 
supporting surfaces of rock are always deeply rugged and hence afford 
a great resistance in friction; and further that the inclination of the 
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