62 FROM NEBULA TO NEBULA 



which 1 have shown both holds and propels the stars 

 and planets in their courses, may be harnessed tx> do 

 the petty chores of man. If gravitation is not itself 

 an absurdity, it should not be, nor seein, more absurd 

 that its pow r er might in some way be rendered reversible 

 (like any and every other form of energy may be) in 

 order to perform useful work. The way is pointed out 

 by Nature herself: it i-s, by transmutation of the force 

 into heat in the bowels of the globe. It has often been 

 proposed to sink a well miles deep to reach the internal 

 fires. If we did so, we should tap sources of gravistatic 

 heat as surely as there is such a thing as weight, or that 

 molecules can store up and deliver energy. If gravita- 

 tion perpetually acts it must be doing work of some 

 sort continually. Then why not in heat? If not in 

 heat, then in what? If in nothing, then is the doctrine 

 of conservation of energy a nullity and gravitation a 

 delusion. It is no answer to say of our postulated grav- 

 itational body that the force is required to keep the 

 particles in their places, for they would stay there any- 

 how, under the law of inertia; as they would also, for 

 the same reason, in the case of the non-gravitational 

 body. 



This cyclical process of converting gravity into heat 

 and heat into gravity again finds a remarkable parallel 

 in the terrestrial transformation of water into vapor, 

 rain, stream and ocean, of which were one link un- 

 known it would be infinitely more difficult to divine. 

 In the solar heat- generating cycle, the descending jets, 

 or geysers, answer to our rain, perpetually flooding the 

 whole of the sun's surface, and falling, with the regular 

 continuity of the Amazon, toward his center, there to 

 suffer evaporation by his pressure instead of by his 

 rays, and thence to rise again in fountains of life-giving 

 warmth. 



