The Laivs of Climatic Evolution. — Manson. 49 
ped,* or are selectively absorbed.! That a gradual accession 
of heat must be thereby inaugurated, resulting in the removal 
of glacial conditions,- and that such removal of glacial con- 
ditions must be on lines determined by the degree of exposure 
to solar energy^ and by the susceptibility of the different por- 
tions of the globe to be influenced by such exposure. That 
these new conditions must inaugurate a new distribution of 
temperatures ranged in zones and subject to solar control. 
The necessary corollaries of these postulates are: 
(a) That a planet having water and air within the sphere 
of its control, and which has not yet exhausted its internal 
heat, must be densely shrouded in clouds, whose outer surface 
presents a high albedo. 
(b) That a planet whose internal heat has been practicallv 
exhausted, and which holds water and an atmosphere within 
the sphere of its control must reflect solar energy deficient in 
those rays which are most readily trapped, or selectively ab- 
sorbed by its atmosphere, and it must have a low albedo, and 
that the color of its reflected rays must be controlled bv those 
least readily utilized and trapped. 
(c) That glacial conditions may exist locally during anv 
period of a planet's climatic evolution provided there be re- 
gions sufficiently elevated; but that an Ice age occurs as its 
oceans are finally exhausted of their available remnant of 
planetary heat, that this age marks the period during which 
surface temperatures pass from interior to exterior control, 
or is the transition period of its climatic evolution, and is 
unique. 
(d) There are two great eras in the climatic evolution of a 
planet: ist, the era during which its internal heat controls 
its surface temperatures, and solar heat acts principally as a 
conservator of interior heat; 2nd, the era of solar control of 
climates, the former being an era of gradually decreas- 
ing temperatures, of uniform distribution at sea level; and 
the latter an era of gradually rising temperatures of a zonal 
distribution. The two eras, so far as land areas are con- 
*Tyndall— Proc. Royal Soc, Vol. XIII, p. 160. Phil. Trans., Vol. 
152, p. 95. Archives des Sciences, torn. V, p. 293. 
fLangley — Investigations on the Action of the Atmosphere on 
Solar Radiation. Mem. Nat. Academy of Sciences, 1885-7. 
Buff — Archives des Sciences, tom. LVII, p. 293. 
