18 



climatic evolution, now in progress upon the Earth, is 

 tending. 



CONCLUSIONS. 



The author therefore holds: (1) that the present zonal 

 distribution of climates is gradually increasing in tem- 

 perature and extent; (2) that this rise in temperature is 

 due to the trapping of solar heat by the lower layers of 

 the atmosphere; (3) that this rise in temperature was 

 inaugurated at the culmination of the Ice Age in tropi- 

 cal latitudes, and that it must be gradually checked by a 

 denser cloud formation as the surface temperatures of 

 the oceans are raised;* (4) that the Ice Age was unique 

 in the climatic history of the earth, and the result of 

 the laws previously cited; (5) that preceding climates 

 were independent of latitude and were controlled by 

 the internal or planetary heat of the earth, that they 

 were the result of the cooling of a hot spheroid sub- 

 jected 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 retarded by the conservative action 

 of solar energy; (6) that local glaciations could have 

 occurred during any period and in any latitude, pro- 

 vided there were land areas sufficiently elevated. 



*The equatorial cloud ring is possibly the nucleus of a more extended 

 ring which will protect a greater area from noon and afternoon exposure 

 to direct solar energy. As evaporation was reduced to a minimum at the 

 culmination of the Ice Age, cloud formation and precipation, being direct 

 functions, were likewise at a minimum and this ring was then probably of 

 less extent. 



