536 
GREAT MASSES OF DRIFT HAVE ACTED LIKE GLACIERS. 
first rush of the waters, would be in the condition of moist pliable masses of great 
weight, which, in every situation that offered sufficient declivity, would be forced 
either by the influence of the superincumbent wave or by their own momentum 
into the adjacent depressions, and like the glaciers of the Alps, would follow the 
inclined planes or main courses of the newly-formed valleys. 
Who that has studied the detritus of mountain chains will not admit, that in 
cubic measure and in weight the masses which now encumber certain narrow 
valleys, wherever their extension into the plains has been checked by local ob- 
stacles, are not as massive and as thick as the highest moraine ever left by a 
glacier ? 
And if so, will any one deny, that such moving masses of gravel, sand and blocks, 
so piled up as to have the full weight of the largest glacier, may not have produced 
the same mechanical results upon their under surface ? If the geologist asserts his 
belief, that such was the condition of things, and also shows that such heaps have 
very frequently fine sand and gravel at their lower extremities, will not the me- 
chanic support him in his opinion, that not only the subjacent rocks over which 
these heavy plastic masses of detritus travelled, but also the sides of the valleys 
against which when confined they pressed, may have been grooved and scored by 
them as well as by a glacier ? The glacier, it is true, travels slowly, whilst under 
our hypothesis, the moistened drift must have moved more rapidly. But might 
not the same effects follow ? Will not a heavy incumbent mass scratch and polish 
by rapid as well as by slow action ? 
Let this view be objected to : still it is clear that no geologist can venture to 
appeal to subacrial phenomena in reference to any of those numerous tracts, the 
coarse detrital accumulations of which were formed under the sea and are often 
associated with marine shells. If we, then, collate the whole of the elements of 
the problem of superficial detritus, including the scoring and polishing of rocks 
and the transport to distant places of huge blocks, and find that in a great 
multitude of cases, a prior submarine condition of things and subsequent eleva- 
tions of mountains, or depressions of adjacent basins are essential postulates, we at 
once confine the application of glaciers to limited centres of action. Freeing 
ourselves from hasty generalizations drawn from a few isolated data, we appeal also 
to other “ verge causaj ” which are still before our eyes, and which were set in 
movement when the surface of the planet underwent great mutations, and when 
the desiccation of vast oceanic regions was accomplished by elevation from beneath. 
