THE GEOSPHERES 439 



the rocks, for there are certain reasons (which cannot now be set 

 forth) for regarding the centrosphere as an aggregation of metal- 

 loid substances, much as the lithosphere is an aggregation of 

 lithoid substances. The blending of the exterior geospheres is 

 especially intimate where the three are in normal contact, i. e., 

 about the terrestrial surface on which men live and with which 

 geographers deal ; and the soils, the plants which subsist on the 

 soils, the animals which consume the plants, and the crowning 

 human organism which dominates all the others are products 

 of the commingling. 



Just as the geospheres are intermingled in material, so they 

 are, in some measure, interrelated in normal movements. The 

 atmosphere is an aerial ocean, ever astir with currents due pri- 

 marily to the rotation and revolution of the sphere, i. e., to move- 

 ments depending on the density and volume of centrosphere 

 and lithosphere ; the waters of the ocean are evaporated into the 

 atmosphere, carried far in its currents as aqueous vapor, and 

 then precipitated to flow back again as fresh water, while the 

 body of the ocean is enlivened by currents set in motion by the 

 ever-moving atmosphere as well as by tides produced by rota- 

 tion and revolution ; the lithosphere is constantly destroyed and 

 reconstructed by the moving waters of the hydrosphere, while 

 the earth-crust is warped and continents are lifted and sea-bot- 

 toms depressed by the obscure but potent movements of the 

 centrosphere. So the normal movements of the geospheres are 

 interrelated ; and most of them, from the rhythmic rise and fall 

 of the earth-crust through which continents are lifted and sub- 

 merged to the trade-winds and oceanic currents, may be traced 

 to the motions of the centrosphere. 



Let us now consider for a moment how the conditions and 

 motions of the exterior geospheres would be affected by cir- 

 cumstances which, at first sight, might seem trivial ; for thereby 

 we may see more clearly how delicate are the interrelations on 

 which terrestrial life and human activity depend. Suppose the 

 temperature of the earth were raised, say, 200° F., what would 

 follow ? Your common sense, born of experience, tells you 

 that much or all of the hydrosphere would cease to exist as 

 such and become a part of the atmosphere ; that the atmos- 

 phere would thereby be multiplied in volume and density, 

 changed in substance, and modified in movements, yet that the 

 lithosphere would remain substantially unchanged save that 

 some of its substance would be dissolved in the densified atmos- 



