I9I4.] "A KINETIC THEORY OF GRAVITATION." 121 



round their common center of inertia in a period of one year, just 

 grazing each other's surface every time they came to the nearest 

 points of their orbits." (Assuming of course that the globes were 

 sufficiently rigid to escape disruption by tidal forces.) 



To aid in forming a mental picture of this last case described by 

 Lord Kelvin, in which the two globes fall together but do not 

 collide, I have made a diagram (Fig. i) of the two elliptical orbits; 

 and in order to show the globes of appreciable size, the orbits are 

 made very much less excentric than Kelvin's premises call for. The 

 globes are shown at perihelion, just escaping collision. Of course, 

 the globes in falling from aphelion to perihelion would gather the 

 same amount of energy that they did in the case of collision, where 

 their motion was arrested and their kinetic energy was thus converted 

 into heat ; but without collision the vast energy acquired during posi- 

 tive acceleration from aphelion to perihelion would disappear during 

 negative acceleration from perihelion to aphelion, and be transformed 

 back to the ether whence it came. 



The sun and planets of the solar system, and the planets and their 

 satellites, because of the excentricity of their orbits, continually go 

 through the same kind of cycle described by Lord Kelvin, differing 

 from that only in degree. For instance, the earth in its six months' 

 passage from aphelion to perihelion falls about three million miles 

 toward the sun, and gains in orbital velocity about five eighths of a 

 mile per second. It thus acquires new kinetic energy from the ether 

 which, if it could be manifested as heat, would be sufficient to evapo- 

 rate all the oceans, lakes, and rivers, heat the dry earth to vivid 

 incandescence, and vaporize much of it ; the earth would become a 

 miniature sun. And all this energy is restored to the ether during the 

 next half year while the earth is moving from perihelion to aphelion. 



With the idea in mind that a falling body gathers energy from 

 the ether, and restores all of it to the ether when raised the same 

 distance against gravitation, by any means, homely examples are at 

 once suggested ; thus, a stone thrown upward and falling again, does 

 it in the reverse order, and a common clock pendulum goes through, 

 and repeats the cycle with almost the regularity of a sun and planet. 



In the theory of gravitation under discussion, the only new postu- 



