The Lazvs of Climatic Evolution. — Manson. 47 
apparently existing upon planets in a less advanced stage. 
If we can predicate the conditions towards which present cli- 
matic developments are tending, these must be the apparent 
conditions of a more advanced planet. Thus the stages 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 de- 
velopment must be represented in a general way by the vari- 
ous stages now attained by one or the other of the planets of 
the solar system. 
The Lazi's of Climatic Evolution. 
. The principal laws of climatic evolution are presented in 
the form of a series of postulates and corollaries. 
(i) Heat rays cannot pass through fogs and clouds, form- 
ed of the vapors of a fluid having the physical properties of 
water, except in very greatly diminished intensity.* 
(2) A hot spheroid floating in space and holding water 
and air (or fluids of similar properties) within the sphere of its 
control, gives ofif and receives heat subject to its passage 
through clouds. The spheroid must lose heat principallv bv 
the expansion of water into vapor and by radiation from the 
cool outer surface of its cloud envelope, which envelope is 
maintained by the evaporation of water by the heat of the 
spheroid, and conserved by heat reaching it from exterior 
sources; during its existence it acts as a conservator of the 
heat of the spheroid. 
(3) That in the stages of cooling subsequent to the forma- 
tion of oceans, land surfaces must, by reason of their low spe- 
cific 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 free by denudations, faults and 
fractures, is principally taken up by water in its fluid and va- 
porous form, and conserved by water in the form of clouds. 
(4) The surface temperatures of such a spheroid nuist be 
practically independent of exterior sources of heat until the 
greater portion of the water surrounding it be reduced to its 
*Maury — Physical Geography of the Sea, 6th Ed., p. 212 et seti. 
Croll — Climate and Time. p. 60. 
Climate and Co.smology, p. 51. 
Geikie, J. — The Great Ice Age, pp. 800-801. 
