48 Tlie American Geologist. January, isw 
point of maximum density or converted into ice, and that prior 
to this stage of its cHmatic evolution, its surface temperatures 
are practically controlled by interior (or planetary) heat, and 
are practically independent of latitude ; and are therefore inde- 
pendent of the temperature to which the outer surface of the 
cloud sphere may be exposed. The effect of variations in ex- 
terior heat being- mainly to increase or decrease the duration 
of the interior supply, and to expand or contract the sphere of 
cloud condensation. The principal function of exterior heat, 
prior to the chilling of the oceans, being conservative or to 
replace in part the heat lost by radiation from the cold outer 
surface of the cloud sphere. 
(5) That until the exhaustion of the available internal 
heat supply, outside of a crust of low conductive power, the 
surface temperatures of the spheroid must be nearly uniform 
from pole to pole, varying only with elevation above sea level, 
or from local causes, such as the influence of lava outbursts 
upon the areas to the leeward of such outbursts. And that a 
series of uniform climates must prevail independent of lati- 
tude, and gradually decreasing in temperature as the spheroid 
loses heat. 
(6) That the low specific heat of land areas permits them 
to cool more rapidly and to reach glacial temperatures before 
the oceans are reduced approximately to the point of max- 
imum density, and consequently that snow must accumulate 
upon these areas until the oceans cease to give ofif sufficient 
vapor to shield the earth from solar energy. That these ac- 
cumulations of snow must reach their maxima along belts of 
maximum precipitation, and must be independent of latitude. 
(7) That upon the chilling of the oceans, the supply of 
vapor maintaining the cloud envelope is cut olT, and the atmos- 
phere deprived of the greater portion of its heat-intercepting 
power; and that heat rays from exterior sources then reach 
the planetary surface in sufficient quantity to dominate its 
climates. That a new distribution of temperatures is thereby 
inaugurated, dependent principally upon latitude or exposure 
to exterior sources, and modified by elevation and local causes. 
(8) That solar rays by contact with the planetary surface 
are partly converted into dark or obscure rays and are trap- 
