GKAVISTATIC HEAT 323 



creases, but at every point of its ascent it has gained a quantity 

 of potential energy equivalent to the kinetic energy lost, and when 

 the body ceases to rise, the kinetic energy vanishes and the energy 

 becomes wholly potential. In every position of the body the rela- 

 tion expressed by the following equality always holds good : 

 Kinetic Energy -f- Potential Energy = A constant. 



When the projected body begins to ascend, its energy is en- 

 tirely kinetic, because while at the surface of the earth the po- 

 tential energy of a heavy body is zero. On reaching its highest 

 point the kinetic energy has vanished, and potential energy ap- 

 pears in its place. As the body descends, the energy is again re- 

 converted from potential to kinetic. In positions intermediate be- 

 tween the highest and lowest points the energy consists partly of 

 one kind and partly of the other, and as the body moves from one 

 point to another, a constant transformation of one form of energy 

 into the other is constantly taking place, subject always to the 

 condition that the sum of the two remain constant. 



You will perceive from this statement that clearance 

 for fall, not the power that causes the fall, is looked upon 

 as the vital factor. Is not this prima facie absurd f 

 Gravity, it is admitted, pulls the object downward before 

 the fall began, during the fall, and after the fall, but the 

 Conservationists deny to its operation the production of 

 any effect save for the short span of the fall and the brief 

 moment of the settling of the object after. It is a clear 

 case of mistaking identities. Proceeding on this mani- 

 festly false tack, our doctrinaires have in all their theor- 

 izing assumed the force of gravity to be innocuous and 

 sterile just when, under the letter and spirit of the law of 

 the inverse square, it rises to its maximum! Let us 

 pursue this train of reflection further : 



Knowing, as we cannot fail of doing, that it is in the 

 nature of gravity to be sleeplessly active in the control 

 and movement of stars and systems, does it not appeal 

 to your reason that it should be equally persistent and 

 cosmically productive in situations where molar move- 

 ment is obstructed? Is it good sense to say, or to sup- 

 pose, that by bringing power and matter in great quan- 

 tity together, there must ensue an end to activity and that 

 Nature thus stupidly engineers her own defeat? If 

 gravitation can whirl about stellar masses with ease and 



