The Evolution of Cli?natcs. — Manson. 165 
Ice age was foreshadowed* and the conditions were svich as to 
favor its extension until the effective exhaustion of the store 
of heat beneath the oceans and resident in them, by reason of 
the high specific heat of water. It will be noted here that 
wherever, in obedience to the expansive force of this waning 
earth heat, a particle of water was vaporized and made the last 
round of its circulation, it returned to the earth in that form 
which stored the maximum degree of cold, and which required 
the action of solar heat to change. 
From the moment that snow began to accumulate, the 
remaining earth heat was available for producing those condi- 
tions favorable to glaciation, namely, warm seas, dense fogs 
and cold continental areas; and the solar energy reaching the 
upper regions of the atmosphere was available for maintaining 
those favorable conditions. f Glaciations under these condi- 
tions would be cumulative until the oceans, partially exhausted 
of their heat, and approximately reduced to the point of max- 
imum density were no longer able to supply the moisture neces- 
sary to shroud the earth from direct solar heat. 
At the expiration of still another interval of time, the 
isothermal surface, having a mean temperature of say 32" 
Fahr., shrunk in upon the globe, and the oceans were still 
further exhausted of their store of heat and their bottoms 
brought in contact with water having a mean temperature of 
31° Fahr., a temperature approximating that of the ocean 
depths at present, and of ice in masses. [j; 
The isotherm 32° Fahr. was a spheroid circumscribing the 
earth. In shrinking to the earth, its intersections with the 
surface were controlled by the elevation of the surface above 
*Probably not until our polar ice caps give place to polar snow- 
caps like those Mars presumably has, which form and melt off with 
the seasons, will the Ice age have departed from our planet. See 
Chapter 7. 
tThe prime objection which is urged against all previous theories 
is their inadequacy. We here have, it seems to the author, a perfectly 
adequate cause — resident earth heat to supply evaporation and shut 
out solar energy, which energy can only act the part of a conservator 
of the glacial conditions until the exhaustion of available earth heat, 
w-hen its power can be spent in melting ice, and in gradually establish- 
ing the present conditions. 
+ Dr. Jas. Geikie seems almost to reach the same conclusion, for in 
rejecting the upheaval theory of glaciation he says — "Now it seems 
easier to believe that the snow line was lowered by several thousand 
feet than that the continents were elevated to the same extent." The 
■Great Ice Age, 3rd Edition, pp. 792-3. 
