THE SOURCE OF ENERGY 27 



converted into the potential energy of food, and so is 

 utilised by life. But the steam and oil engine also 

 work by virtue of the energy of the sun, which, in 

 bygone times, was stored up by great masses of 

 vegetation, and is now preserved in coal and fuel. 

 Potential energy, or energy on the leash, is not 

 capable of being apprehended until it is converted 

 into kinetic energy. Ignite coal and its potential 

 energy a form of chemical energy turns, like that 

 of a released spring, into kinetic, and the molecules 

 of the burning coal are suddenly thrown into a state 

 of intense chaotic motion, which we call heat. But 

 vital energy or vital force, the energy of a man 

 working or living, are not special and peculiar to life. 

 They are one with the great flow of inanimate energy 

 reaching us from the sun, which bears the whole 

 world along. 



Energy, someone may say, is a mere abstraction, 

 a mere term, not a real thing. As you will. In 

 this, as in many another respect, it is like another 

 abstraction no one would deny reality to, and that 

 abstraction is wealth. Wealth is the power of 

 purchasing, as energy is the power of working. I 

 cannot show you energy, only its effects. I cannot 

 show you wealth, only its effects and its purely 

 conventional symbol, money. Money is not wealth 

 to a starving man in a deserted place. It is both a 

 symbol and a measure of wealth earned, as work 

 done is a measure of energy expended. Heat energy, 

 mechanical energy, chemical energy, and so on, are 

 different forms rather than different kinds of energy, 

 just as coins, bank-notes, cheques, and so on, are 

 forms of money. The bank-teller totals up a hetero- 

 geneous collection of coins, paper money, securities 

 of various kinds and currencies, all as one sum of 

 money, and then thinks of that sum, not of the 

 sovereigns and shillings, notes and cheques he was 



