334 Glacial Period in the [July? 
America there is the same evidence of the land having 
been covered with water which was not that of the sea ; as 
the deposits left by it do not contain marine remains. If 
wo may suppose that a similar mass of ice accumulated 
around, and spread from the Antarctic as from the Arctic 
regions, and that ultimately a prolongation or arm of that 
icy mass reached the eastern coast of South America, so 
as to dam back the streams as far as the Rio Plata, we 
shall have, I believe, a complete explanation of the deposi- 
tion of the Pampean mud and the Patagonian gravels, and 
of the destruction of the great mammals and the entomb- 
ment of their remains. 
The present physical geography of the world and the 
existing distribution of its inhabitants were immediately 
preceded by a wide-spread entombment of land animals, un- 
paralleled elsewhere in the geological record. In lake basins 
and estuaries of Eocene and Miocene age there have been 
preserved abundant remains of land animals, more especially 
in connection with the movements of elevation of certain 
mountain chains and the volcanic phenomena that accom- 
panied them ; but, compared with that which we are dis- 
cussing, these entombments are insignificant and partial. 
The destruction of life that took place in the Glacial period 
was continental, if not world-wide, in its extent. The de- 
posits in which the remains are found were not formed in 
old lake basins ; they fringe, and in some cases nearly over- 
spread, the continents, or run in great arms up the larger 
valleys. Here and there in America, Europe, and Asia, 
there are isolated deposits containing the remains of tertiary 
mammals, but the bones of the glacial mammals are spread 
over all the northern parts of the northern continents, and 
in South America are of equal extent. 
The blockage of the coasts by ice flowing down the ocean 
beds seems just such an event as would bring about the 
destruction of life and the entombment of the remains of 
which we have so much evidence. I shall have to return to 
the consideration of the possibility of such a mass of ice 
having advanced northwards from the Antarctic circle when 
we have examined the evidences of glaciation in New 
Zealand ; but let us assume now for a moment that such an 
accumulation did take place, and that it flowed down the 
eastern coast of South America ; then, as it blocked up the 
drainage of each great valley, progressively from the south, 
northward, the waters pounded back would rise and over- 
whelm the animals living on the plains. The nature of the 
deposits favours this supposition. The lowest parts, or 
