of climatic development reached by other planets should 

 afford evidence as to the accuracy of our interpretations. 

 In other. words, the past and future stages of the earth's 

 climatic development must be represented in a general 

 way by the various stages now attained by one or the 

 other of the planets of the Solar System. 



THE LAWS OF CLIMATIC EVOLUTION. 



The principal laws of climatic evolution are presented 

 in the form of a series of postulates and corollaries. 



(1) Heat rays can not pass through fogs and clouds, 

 formed of the vapors of a fluid having the physical 

 properties of water, except in very greatly diminished 

 intensity.* 



(2) A hot spheroid rotating in space and holding 

 water and air (or fluids of similar properties) within the 

 sphere of its control, gives off and receives heat subject 

 to its passage through clouds. The spheroid must lose 

 heat principally by the expansion of water into vapor 

 and by radiation from the cool outer surface of its cloud 

 envelope, which envelope is maintained by the evap- 

 oration of water by the heat of the spheroid, and con- 

 served by heat reaching it from exterior sources; dur- 

 ing its existence it acts as a conservator of the heat of 

 the spheroid. 



(3) That in the stages of cooling subsequent to the 

 formation of oceans, land surfaces must, by reason of 

 their low specific heat, cool faster than oceans; and that 

 heat reaching the planetary surface by the circulation 

 of meteoric or included water or by convection, or set 



*Maury — Physical Geography of the Sea, 6th Ed., p. 212 et seq. 

 Croll— Climate and Time, p. 60. 



Climate and Cosmology, p. 51. 

 Geikie, J.— The Great Ice Age, pp. 800-801- 



