681 
endeavoured to explain not only the scratches and polish of hard 
submarine rocks, but also why large blocks are often found on former 
submarine hills, and why (in Russia at least) such blocks are more 
frequently associated with clay than sand. These views were indeed 
first expressed at the Glasgow meeting of the British Association, 
when I strove to reduce a large portion of the Alpine glacial theory 
to considerations depending upon the fact, that during the era of 
the dispersion of the large blocks, by far the greater portion of our 
‘cqntinents were beneath the sea. 
Mr. Maclaren, to whom [ have already adverted, has recently im- 
proved this view, by showing how the parallel scratches and grooves 
ranging from N.N.W. to 8.S.E., and the dispersion of blocks in that 
direction, are reconcileable with the union of currents from the N., 
set in action, as above supposed, by a great polar elevation which 
acted as a “ centre of dispersion ;” but, as this author adds, a broad 
current would also set continually eastward along the immersed re- 
gions included in the temperate zone ; and hence, he says, that when 
the icebergs were drifting southwards from the poles, they would na- 
turally be carried to the S.E. by a stream compounded of the two 
currents. After reasoning upon the wide application to which the 
view of floating iceberg action is capable, and how many of our pre- 
sent terrestrial appearances it will explain, Mr. Maclaren adds, “ Mr. 
Murchison’s hypothesis, if adopted, does not exclude that of Agassiz. 
On the contrary, it may be assumed, that while the glacial condition 
(which caused the great accumulation of ice in the northern re- 
gions) continued, every mountain chain, which then had an eleva- 
tion of 2000 or 3000 feet above the sea, would be encrusted with 
ice, perhaps as far south as the latitude of 40°. Each of these would 
be on a small scale what the polar nucleus was on a great scale, a 
centre of dispersion.” 
In the memoir upon Russia by M. de Verneuil and myself, one 
observation, however, occurs which has not found its way into the 
abstracts, and which, therefore, I may advert to, as explaining why 
the rough detritus of mud, sand, clay and boulders so very seldom 
contains marine remains. Such heaps are made up cf materials 
which we consider to have been imbedded in a true terrestrial glacier, 
and therefore, though detached, and flcated to a distance, they never 
could afford more than ¢errestrial detritus; and if to this be added 
the consideration of how the stranding of such masses would destroy 
animals in the vicinity, as suggested by Darwin, we may rationally 
conceive why so few shells have been discovered in this coarse de- 
tritus, whilst we readily perceive why the stones impacted in it should 
be scored and striated, and often polished. 
Besides the great advancement of our knowledge of terrestrial 
magnetism, which at some future day may be connected with our la- 
bours, the Antarctic expedition, under the distinguished navigator 
Captain James Ross, has, as might have been expected, thrown con- 
siderable light upon the glacial theory. A few years only have 
passed since the existence of an enormous mass of ice-clad land in ~ 
the antarctic region, was announced by an American squadron of 
