450 Climate of the Glacial Period. (October, 
a depression, of the land,—on the theory that it was move- 
ments of the earth’s crust that brought it above and sank it 
below the sea. Now, in various places in the south of 
England, we have marine deposits a little older than the 
forest bed of Cromer: they occur mostly between the present 
tide-marks,—never higher than we may suppose the tide to 
have reached before the Straits of Dover were cut through. 
Therefore, if the surface of the land has oscillated, it is re- 
markable that it should have returned to the same level as 
it stood at before the Glacial period; but such a fact is 
clearly in unison with the idea that it was the mobile water 
that had retreated and returned. These submerged forests 
are not confined to Europe, but are found on the coasts of — 
America,—as in the Bay of Fundy,—betokening that their 
occurrence belongs to a general and not to a local cause. 
Another class of phenomena, usually ascribed to a gradual 
sinking of the earth’s crust, but which might also be pro- 
duced by the return of the sea to he level it stood at before 
the Glacial period, is that connected with the growth of 
coral islands. Darwin’s celebrated essay on their formation 
first proved that they were due to the gradual deepening of 
the water. Dana, closely following Darwin in his theory, 
estimates that this deepening of the ocean bed from which 
the coral islands rise has been at least 3000 feet, and that 
the subsidence to which he ascribes it extends round one- 
fourth of the earth’s circumference in the Pacific, being 
indicated by atolls in that ocean for 6000 miles in length 
and 2000 in width. In the Atlantic he considers that “‘ the 
Bahamas show by their form and position that they cover a 
submerged land of large area, stretching over 600 miles 
from N.W. to S.E. The long line of reefs and the Florida 
Keys trending away from the land of Southern Florida are 
evidence that the Florida region participated in the down- 
ward movement.’’* 
Nor are these indications of either a subsidence of the 
land or a rise of the level of the ocean since the Glacial 
period yet exhausted. C. F. Hartt considers he has found 
proofs in Brazil that that country stood higher when it was 
glaciated than it nowdoes.t Dana has argued the same 
respecting the high latitudes of North America. There is 
hardly a mountain chain of the world that has not been 
supposed to have stood higher, to account for the lowering 
of the snow-level on its sides in the Glacial period. The 
Himalayas, the Alps, the Caucasus, the Pyrenees, the 
* Coral Islands, 1872, p. 366. 
+ Geology and Physical Geography of Brazil. By C. F. Hartt. P. 573. 
