Perry.] 86 [February 28, 
ing to our author, only somewhere from 40 to 65 or 70 feet below its 
present level. Under these circumstances it is evident that the de- 
pression in question could have had, at the best, only a very limited 
effect on the climate. Such a submergence, or one even of 500 feet, 
must have left the ice mountain-high all over this region. Indeed, 
the ice would have continued to stand far above the sea, in case it 
were at its present level, and especially if the surface of the ocean 
had been considerably lowered by the immense loss of water 
caused by experienced in the formation of the ice sheet. But, 
even admitting that the land was slightly depressed, we do not 
get rid of all difficulty. It seems to be forgotten that a submergence, 
in order to be effective, either in changing the climate or in the wast- 
ing of ice, must be great. Submerged ice scarcely melts at all, unless 
it be in water having some ten or twelve times its own volume, and 
unless the surrounding temperature be comparatively high. Now 
these conditions must have been wanting, according to Prof. Dana’s 
suppositions interpreted in the light of facts, so far as I can make 
them out. Indeed the ice-mass, in spite of the conjectured depres- 
sion, must have continued broadly to spread over the continent, as it 
probably stood high above the ocean during the closing stage of the 
glacial times. Unless, therefore, there had been a change of climate 
from some other cause or causes, the ice, so far as we can now see, 
could not have wasted, but must have remained as it was—unthawed 
for ages. 
Meanwhile, however, there is peculiar evidence of an astronomic 
kind which ought not to be overlooked. As the earth appears to 
have been, at what was perhaps the beginning of the glacial period, 
in a position relative to the sun and the planets favorable to a greater 
degree of cold, so, toward its close, it was in an attitude probably 
suited to induce a return of warmth, and with it to cause the long 
winter in due time to come to a close. Whatever theory is held in 
respect to this matter the facts none the less exist, if we may trust the 
calculations of astronomers; and to all appearances they are certainly 
very significant. _ But this point must be left with the simple query 
whether it does not deserve a far closer investigation than it has yet 
received from either the astronomer or the geologist. Such a change 
of climate accordingly occurring, whatever may have been the 
cause, a time of waste was sure to follow. The main sheet of ice 
1 Paper cited, pp. 48, 66. 
