50 The American Geologist. January, i899 
cerned, must be separated by an Ice age. The difference in 
the specific heat of land, and that of water, permits the land 
areas to cool first. The precipitation of snow upon them must 
therefore have been cumulative, until the oceans were reduced 
to about the point of maximum density. 
It is reasonably certain that glacial conditions were first 
removed frpm equatorial regions, and that maximum glaci- 
ation of land areas in temperate latitudes may have occurred 
subsequent to the inauguration of solar control over equa- 
torial latitudes, and that polar glaciations may have reached 
their maxinuun at a period subsecpient to the commencement 
of the disappearance of glaciations in temperate latitudes. 
(e) The accession of solar heat by the trapping jjroces^ 
being the result of a positive difference between the rate of 
receipt and the rate of loss, and not being a function of th ^ 
orbital distance, a rise in temperature may as certainly follow 
in one position as another. 
(f) That glacial conditions, although imposed upon lines 
independent of solar exi;)Osure, must have reached their max- 
imum upon areas subject to maximum precipitation, and as 
the movement of the atmosphere in temperate latitudes is to- 
wards the east, the west coasts of continents are more ex- 
posed to moist winds and hence were more deeply glaciated 
than the east coasts. The narrow North xA.merican continent 
was thus more exposed to glaciation from the wide Pacific, 
than was the broad Euroasian continent from the narrow 
.\tlantic. 
fg) That the northern hemisphere of low s])ecific heat 
has progressed further in climatic development than has the 
southern hemisphere of high specific heat. Similarly, the 
Atlantic has been warmed to a greater extent than the 
Pacific* 
*It will probably be noted that no mention is made of light rays; 
these can be filtered out by clouds and pass through in greatly dimin- 
ished intensity. It is not considered necessary to discuss their in- 
fluence at this point, as their effect is slight at temperature approxi- 
mating the freezing point. The gradual development of visual organs 
and the development of all other senses prior to that of sight are lines 
of investigation which the author has not been permitted to make for 
want of time and means. 
