Tlie Evohition of Climates. — Marison, 171 
elusion, namely: That when a body enveloped in media hav- 
ing heat trapping power (or the power of selectively absorbing 
radiant energy) is exposed to a beam of heat rays from an ex- 
terior source, a gradual rise in temperature must follow. 
A gradual rise in temperature was thus inaugurated when- 
ever solar heat rays were permitted to reach the surface, for 
they are there converted into dark heat rays, which are trapped 
or selectively absorbed by the atmosphere. This rise must 
follow whether solar energy be constant or slowly decreasing, 
the rise being due, not to the actual amount of heat received, 
but to a positive difference between the rate of receipt and the 
Tate of loss. 
The great increase of mean surface temperature in equa- 
torial, temperate, and sub-polar areas can be accounted for by 
this small but positive dilTerence between the rates of receipt 
and loss; as has just been shown, this action is yet in progress. 
These -deductions are radically at variance with the opinion 
of high authorities on meteorology, as may be seen from the 
following quotation: 'Tt is evident that our planet, considered 
as a whole, and on the average of many years, loses all the 
Tieat that it receives from the sun, but all the details of this pro- 
cess have not been worked out."* 
The author is vmable to find any facts to sustain this view — 
all tend to refute it. 
The trapping of heat by vapors and gases of the atmosphere 
— the gradual retreat of glaciers in both hemispheres — and the 
vast rise in temperature since the culmination of the Ice age — 
all corroborate the deductions just reached — namely, that the 
mean surface temperatures of the globe have been and are yet 
rising by the trapping of solar heat. 
It does not follow that this rise has an indefinite or exces- 
sive limit, for as the oceans become warmer they are cooled by 
giving ofT more vapor. This vapor, when partly condensed 
into clouds, intercepts solar heat in the upper atmosphere, and 
the intense white of the upper surface of clouds reflects more 
heat into space than the darker planetary surface beneath. 
The vast store of cold in the continental ice sheets has been 
greatly, exhausted ; there yet remains the vaster store in the ice 
*Dr. Cleveland Abbe, U. S. Meteorological Bureau. Am. Jour, of 
rScience, May, 1892, Vol. XLIII, p. 364. 
