Editorial Comment. iij 
2. That during this time of earth-controlled climate, the 
direct rays of the sun were shut out from reaching the earth by 
a surrounding mantle of clouds of aqueous vapor produced by 
the evaporation of water from the heated earth ; solar energy 
promoting a conservation of the planetary supply. 
3. That as the earth became cooled, land masses, by reason 
of low specific heat, lost their heat first. The cloudy envelope 
was attenuated and finally dissipated admitting the sun's rays 
and inaugurating the present system of sun-controlled climates. 
4. That this change took place after the earth's surface and 
the water of the oceans had reached a very low average degree 
of heat. The oceans ceased to give off a sufficient amount of 
watery vapor to form the cloudy envelope after the lands had 
cooled so low as to become extensively glaciated. 
5. The difference in specific heat and in the rate of cooling 
between the land and the water of the earth, while causing the 
glaciation of the lands, did not act sufficiently long to cause 
the congeajation of the oceans. It was interrupted by the ad- 
vent of the sun's rays and the inauguration of the present 
zonal system of solar climates. 
6. Since the inauguration of solar or zonal climates, there 
has been an increase in the average temperature of the earth's 
surface, (i) by absorption of heat derived directly from the 
sun; (2) by the trapping action of the atmosphere upon the 
long wavelength rays of heat emitted by the warmed planetary 
surface; and (3) by convection currents which have distribut- 
ed more evenly the heat thus accumulated. This rise in tcm- 
j>erature is most notable in tropical and temperate latitudes, 
and it has caused and still continues to cause the retreat of gla- 
cial conditions in all latitudes. 
7. That the gradual transition from earth control to sun 
control was the epoch of the ice age, although the climates of 
tropical latitudes probably felt some of the effects of this tran- 
sition prior to the culmination of the ice age. 
Some of the previous treatments of this great problem in 
terrestrial physics have wandered so far from certain estab- 
lished and fundamental principles, or have been based upon 
assumptions which apparently disregard these principles, that 
the author has evidently been particularly careful to bring them 
forward and to base his presentations and arguments thereon. 
