THE GEOSPHERES 441 



wash the frozen globe, leaving continents and islands rising 

 above its surface in a geographic configuration differing .not 

 greatly from that of the present. Over this globe no air would 

 float, save possibly a light vapor scantier than the aqueous vapor 

 now borne in our atmosphere; and no man or beast or plant, no 

 trace of life could exist. 



Consideration of the profound modification in the exterior 

 geospheres necessarily following changes in temperature which 

 can only be considered as slight in comparison with the wide 

 temperature range even of our solar system aids us in under- 

 standing something of the conditions which attended the early 

 stages in the development of our'planet. The earth as a whole 

 is apparently a cooling body, though the rate of cooling may 

 be — indeed must be — almost infinitesimally slow. So the 

 planet primeval must have been warmer, a greater part of its 

 water must have been afloat as vapor in the atmosphere, which 

 must have been heavy with vapors and the fumes of solids 

 soluble in hot water. In like manner the changes necessarily 

 produced in the geospheres by diminished temperature enable 

 us to take a long look into the future and foresee the fate which 

 awaits the aging planet — unless, indeed, this fate may be averted 

 by aid of human ingenuity. There are many indications that 

 the mechanism of the solar system, and, indeed, of the stellar 

 system, is running down. We know that the water of the 

 earth is going into new Combinations from time to time as a 

 constituent of the rocks of the lithosphere; we know that the 

 water area of the globe is diminishing from age to age as the 

 eons run, for the clastic deposits with which geologists are most 

 concerned were laid down, in water, while those now forming 

 are largely if not mainly accumulated on land ; there are deserts 

 on every continent today, while the record of geology indicates 

 that during the Carboniferous and earlier ages all the lands of 

 the earth were fertile and humid. And just as the hydrosphere 

 is going into the lithosphere by chemic absorption as well as by 

 interpenetration, so the commingled oxygen and nitrogen of the 

 atmosphere are slowly seperating and combining with the sub- 

 stances of the lithosphere, and probably also with the substance 

 of the hydrosphere. The changes yield a glimpse of planetary 

 history ; they suggest a time when the now deep-buried centro-. 

 sphere was enveloped only by heavy atmosphere, with no litho- 

 sphere save possibly its own scums and slags, and no hydro- 

 sphere save possibly viscid lakes of its own substance half 



