GEOLOGICAL CLIMATES 
303 
The oceans, at these temperatures, do not generate sufficient 
water-vapor to maintain more than the present 52 per cent of 
cloudiness which admits solar energy to the lower and denser 
strata of the atmosphere and to the earth’s surface, which it 
warms. The earth then emits long wave radiations which are 
trapped or absorbed in the atmosphere. This process, within 
certain reasonable limits is cumulative, and results in a gradual 
amelioration of the conditions of Pleistocene time. The oceans 
at the higher temperatures of pre-Pleistocene time maintained a 
far denser and more continuous cloudiness, which shut in earth- 
heat, and intercepted and utilized solar energy in the upper at¬ 
mosphere as a further conservative influence. 
• That the interposition of this cloud-sphere imposed two highly 
conservative conditions upon the further conservation of earth- 
heat: (a) The moist air and clouds are practically impenetrable 
to the radiations emitted by the planetary surface, and the loss 
of this heat through these media was restricted to the interchange 
of water in its various forms in the atmosphere and of the action 
of cyclonic and anti-cyclonic circulation as fixed by solar radia¬ 
tion; (b) solar radiation as a source of heat was restricted to 
the part of a conservator of earth-heat by its absorption and 
utilization upon and above the cloud-sphere, and was admitted to 
the lower regions of the atmosphere and to the planetary surface 
as a controlling factor by reason of impairments in the cloud- 
sphere. 
That continents thus protected from solar radiation, and by 
reason of low specific heat and elevation, frequently reached 
Glacial temperatures during the intervals between outbursts of 
earth-heat from the forming crust, during which intervals ade¬ 
quate earth-heat was not available to prevent glaciation, nor was 
solar radiation available by reason of the intercepting cloud- 
sphere. They were also exposed under the same condition to two 
periods of maximum glaciation, first in the regions of cold, down¬ 
cast currents on anti-cyclonic latitudes, and later to the chill of 
final refrigeration in Pleistocene time. 
That during geologic time, as now, the functions of solar 
radiation prevailed in fixing zones, or belts of cyclonic and anti- 
cyclonic circulation, of maximum and minimum barometric pres¬ 
sure of consequent cloud densities and belts of maximum and 
