174 G. F. Becker—T. “mperature and Glaciation. 
Hitherto it has been assumed that the warming of the sea, 
the evaporation and the precipitation, leading to the formation 
of a particular glacier take place under a sun heat of equal 
intensity, as would happen if there were no ocean currents and 
all these processes went on in the same latitude. Were this 
the case the lines of maximum glacier formation would first 
touch the earth as infinitesimal circles at the poles, and would 
thence move toward the equator remaining parallel to it. At 
any given period, maximum glaciation would be an event of 
the past throughout those portions of the globe lying north of 
the northern glacial isotherm and south of the southern one, 
while between them it would not have been reached. <A differ- 
ent result must necessarily follow from the presence of open 
seas, for it is the most familiar fact in physical geography that 
heated waters from the tropics move poleward. Let it be sup- 
posed that at a given time in any given latitude distant from 
the equator there were no oceanic currents, and that the maxi- 
mum of glaciation compatible with this condition of things bad 
just been reached. If the barriers to the movements of the sea 
were then removed, water more highly heated than that charac- 
teristic of the latitude would flow in from the direction of the 
equator. An increase of evaporation and of precipitation would 
of course result, and the glacial isotherm would withdraw to a 
slightly higher altitude, but the sun’s melting power would be 
unaffected and an immense increase would take place in the 
accumulation of névé. The action of aérial currents would be- 
similar. 
In the tropics, the conditions would be reversed. When the 
world is so cold that the glacial isotherm intersects the moun- 
tain slopes near the equator, the san will not have its full effect 
upon the sea which constantly loses heated waters and receives 
cold currents. The glaciation at the equator will therefore be 
less than it would have been, had the surface waters been pre- 
vented by land barriers from seeking the poles. The glacial 
isotherm at the equator will be slightly lowered by the cooling 
of the ocean, but not in full proportion to the decrease of 
tem perature at sea-level. : : 
It follows that the rate of decrease of temperature with altt- 
tude will be more abrupt at a distance from the equator, during 
maximum glaciation, than it will be at that line when glacial 
formation there reaches its most rapid development, and since 
both evaporation at sea-level and the rate of decrease of temper- 
ature in the snow belt will be greatest in high latitudes, 16 18 
there that the extreme development of glaciers in the entire 
history of the earth, must take place. This highest develop- 
ment or absolute maximum of glaciation will occur where the 
. 
influence of the warm oceanic currents is greatest, or where the 
