24 J. Croll— Cause of Mild Polar Climates. 
stances, be free from ice quite up to the north pole may be, I think, 
securely inferred from what, in the present condition of the globe, 
ice-bound and open seas in the northern hemisphere 
and of the southern ocean abounding in icebergs, but probably 
nowhere ice-bound up to the very coast of the cireumpolar Ant- 
arctic continent, except in more or less land-locked bays.” . . 
“« Suppose now the sea, unobstructed by land from either pole to 
temperate or tropical regions, to be iceless at any time, would it. 
continue iceless during the whole of the sunless polar winter ? 
Yes, we may safely answer. Supposing the depth of the sea to be 
not less than 50 or 100 fathoms, and judging from what 
for certain of ocean currents, we may safely say that dieroniees 
of specific gravity of the water produced by difference of tempe- 
rature not reaching any where down to the freezing point, would 
cause enough of circulation of water between the polar and tem- 
perate or tropical regions to supply all the heat radiated from the 
water within the Artic circle during the sunless winter, if air con-- 
tributed none of it. Just think of a current of three’ quar i of 
és 
twenty-four hours, a little more than water enough to cover the 
whole area to a depth of 1 ieee ; and this, if 7:1° Cent. above the 
freezing point, would bring in just enough of heat to prevent 
freezing, if in twenty-four hours as much heat were radiated away 
as taken from a tenth of a fathom of ice-cold water would:leave: 
it ice at the freezing point. This is no doubt much more than 
the actual amount of radiation, and the supposed current is prob- 
ably much less than it would be if the water were ice-cold at,the 
pole and 7° Cent. at the Arctic sivtle: Hence, without any assist- 
ance from air, we find in the convection of heat by water alone, a 
sufficiently powerful influence to prevent any freezing up in olar 
regions at any time of eae — Trans. of the Geol. Soe. of Glas- 
gow, 22d February, 1877. 
hat an amount of warm water flowing into the Arctic 
Ocean equal to that assumed by Sir William Thomson, along 
with the effects of clouds, wind, dew, and other agencies to 
which he refers would wholly prevent the existence of perma- 
nent ice in those regions, is a conclusion which, I think, can 
hardly be doubted. a is with the pest deference that I 
