286 FROM NEBULA TO NEBULA 



Furthermore, Conservationists in their blind zeal 

 confuse the element of force with the element of veloc- 

 ity, and claim, for example, that a mountain resting on its 

 base produces no mechanical effect, for the bare reason 

 that it is not in motion. The formula by which they thus 

 conjure is this: 



E = 1/2 MV 2 



in which M is the mass, V the velocity, and E the energy. 

 Obviously, if there be no movement, V becomes zero, and 

 the substitution of this value in the equation, be the mass 

 as big as it may, will reduce the energy to nothing. No- 

 body denies that gravitation continues to go on drawing; 

 but we are told that, once settled on a permanent base, 

 the weight of an object, whether a mole-hill or a moun- 

 tain, counts for nought. 



Scientists, furthermore, divide available energy into 

 two sorts potential, or that which stands in reserve 

 against future use, and kinetic, or that which is in the act 

 of doing work, or being converted. In order to get the 

 scientific view authoritatively before the reader let me 

 present this extract from the illuminating essay on En- 

 ergy by Professor John Gall, formerly of Canning Col- 

 lege, Lucknow : 



A reservoir of water situated on the summit of a hill is more 

 valuable than the same body of water at a low level. This is 

 owing to the store of energy which it possesses in virtue of its 

 position ; and as the water descends this energy may be turned to 

 good account in driving machinery. If the reservoir is situated 

 at a lower level than the machinery the water becomes useless 

 as a motive power. A cross-bow when bent, the main-spring of 

 a watch coiled up, a labourer primed for work with a sufficient 

 supply of food, are instances where the energy is due to position. 



We have already seen that when a body is projected verti- 

 cally upwards it possesses kinetic energy in virtue of its motion. 

 As it ascends its velocity and consequently its kinetic energy de- 

 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. 



