56 The American Geologist. January, i899 
controlled by the internal or planetary heat of the earth, that 
they were the result of the cooling of a hot spheroid subjected 
to the gradual loss of heat by the evaporation of water to 
vapor, by the radiation of heat from the cool outer surface of 
the resultant cloud sphere, which loss by radiation was re- 
tarded by the conservative action of solar energy; (6) that 
local glaciations could have occurred during any period and in 
any latitude, provided there were land areas sufficiently ele- 
vated. 
Difficulties in Previous Explanations. 
The postulates and corollaries just given appear to the 
author to satisfactorily account for the great variations in 
climate geologically recoided in the history of our planet. 
The difificulties met with in previous attempts to explain 
present, glacial and pre-glacial climates have been due in part 
to a failure to give due weight to certain of the laws which 
are above cited, and to fully recognize the force of others. 
For instance: 
(i) The influence and functions of water in its various 
forms upon the mode and rate of loss of planetary heat have 
not been given due weight. 
(2) The effect of the difference in the specific heat of 
land and water has been omitted in most of the discussions. 
(3) The conservative function of solar energy prior to 
the exhaustion of planetary^ heat has not been fully recognized. 
(4) The ultimate influence of the trapping of solar en- 
ergy in the lower layers of the atmosphere, and the cVimulative 
effect of this action upon surface temperatures has been left 
out of consideration. 
(5) That the acceptance of ice action alone as a proof of a 
glacial epoch is not warranted. 
The failure to fully weigh and adjust the effects of the 
laws of climatic evolution has almost necessitated a resort 
to assumptions and hypotheses, some of which have been of a 
vague and indefinite nature, and others rest upon an inade- 
quate foundation. Of these may be cited: Variations in the 
amount of solar energy, in the heat absorbing power of the 
solar atmosphere, in the temperature of space, in the direc- 
tion and temperature of the gulf stream, in the elevations and 
depressions of land areas, and in changes in position of the 
