442 THE GEOSPHERES 



liquefied b} T relief from pressure like the lavas of later time ; 

 they raise visions of slowly segregating waters and accumulating 

 rocks formed through interaction between the condensing at- 

 mosphere and the cooling centrosphere ; they indicate the 

 differentiation of the geospheres in nice adjustment to tempera- 

 ture and other conditions. The changes indeed give a threat of 

 ultimate absorption of air and water into the rocks, leaving a 

 dead planet of centrosphere and lithosphere only, swinging 

 helpless through space like our frozen moon ; yet there is a 

 faint promise in a fifth geosphere produced through delicate 

 interaction among the three exterior spheres of the earth, lying 

 about the common boundary of the three, dependent on all, 

 yet able (at least in some measure) to control their relations — a 

 psychosphere, comprehending the scanty but potent and ever- 

 growing mantle of thought which today envelops the world. 



Just a few words more, if you please, concerning the general 

 relations among the geospheres: The atmosphere is a body of 

 gas conditioned primarily by temperature ; the hydrosphere is a 

 volume of liquid conditioned by temperature and gravity ; the 

 lithosphere is a shell of rock conditioned by temperature, gravity, 

 and a more complex chemic affinity than is found in the mix- 

 ture air or the compound water; the centrosphere is a transolid 

 and probably metalloid body, conditioned in ways that are not 

 well known ; the several geospheres combine to form a planet 

 conditioned by temperature, gravity, chemic affinity, and per- 

 haps other agencies, which extend to other planets and satel- 

 lites and suns of the cosmos. So the features of the geospheres, 

 i. e., the characteristics of our planet, are largely determined from 

 within ; yet it is not to be forgotten that each geosphere con- 

 tributes to the making of the others, and thus to the molding of 

 the planet and in some measure to the shaping of the cosmos. 

 This has already been indicated incidentally. 



Let us now proceed to consider a few of the special relations 

 among the geospheres which affect cosmic economy : We have 

 good reason for supposing that the earth is a cooling body, that 

 some of its primeval heat is constantly passing into space to 

 affect (howsoever infinitesimally) other bodies ; but do we know 

 why the temperature of the earth is not lowered more rapidly — 

 why the lowering is so slow as not to be detectable by the ob- 

 servations of history ? We know that if the earth were simply 

 a ball swinging through interstellar space and cooling by the 



