GEOLOGICAL CLIMATES 
301 
>- 
SECULAR CHANGES OF GEOLOGICAL CLIMATES 
By Dr. Marsdj:n Manson 
Berkeley, California 
t 
i 
(■ 
In his masterly essay on “Climate and Cosmology” Croll astutely 
observes, that the most important problem in terrestrial physics 
. . ■ . and the one which will ultimately prove the most far- 
reaching in its consequences, is: What are the physical causes 
which led to the Glacial Epoch and to all those great secular 
changes of climate which are known to have taken place during the 
geological ages ? 
In attempting to interpret the secular changes of past climates 
upon a basis of limited and fluctuating supply of earth-heat and 
its cognate energy, radio-activity, converted into heat, under the 
highly conservative conditions imposed by water in its various 
forms, and the utilization of solar energy as a conservative factor 
throughout geologic time, as competent to maintain the narrow 
limits of temperatures known to have prevailed; and under these 
conditions a limited supply of earth-heat is recorded as a con¬ 
trolling factor during all geologic periods until the inauguration 
of the sole control in the Modern Era of the greater and more 
constant source, solar energy, appeal is made only to those fac¬ 
tors which have probably always been of importance in deter¬ 
mining the character of climates. 
That a logical application of the known principles of atmos¬ 
pheric physics, of the heat-conserving functions of water in 
its several forms and their action upon radiant energy, of the 
intermittent liberation of heat from the non-conducting crust by 
ruptures and by its exposure to denudation and to the setting free 
of radio-active energies, of the further conservation of this heat 
through the utilization of solar energy in and beyond “the true 
