THE ORGANISM AS A MECHANISM 53 



is released most of it is recovered. But we may 

 dissolve the spring in weak acid without allowing it 

 to uncoil. What then becomes of the energy imparted 

 to it ? We are compelled to say that it has changed 

 the physical condition of the solution into which it 

 passes, either becoming potential in this solution, or 

 becoming dissipated in some way. Yet again we cannot 

 trace this transformation experimentally though we 

 may be quite sure that all the energy potential in the 

 coiled spring is conceivably traceable. Suppose, again, 

 we burn some hundredweights of coal in a steam- 

 boiler furnace. Heat is evolved which raises steam 

 in the boiler, and the steam actuates an engine, and 

 the latter exhibits measurable kinetic energy. Where 

 did this come from ? It was potential in the coal, 

 we say, though no method known to physics enables 

 us to prove this by mere inspection of the coal. We 

 must cause the latter to undergo some transformation. 

 But by rigid methods we can estimate very exactly 

 the potential energy of the coal, and we can calculate 

 the kinetic energy equivalent to this. Yet again 

 we find that the kinetic energy of the steam-engine is 

 only a fraction of that which calculation shows us is 

 the equivalent of the kinetic energy of the coal. What 

 becomes of the balance ? We can be quite certain that 

 it has been dissipated in friction, radiation, loss of 

 heat by conduction, loss of heat in the condenser, 

 and so on, although we cannot prove this rigidly by 

 experimental methods. 



Think of the universe as an isolated system. It 

 contains an invariable quantity of energy. This 

 energy may be that of bodies in motion — suns, planets, 

 cosmic dust, molecules, etc. — when it is kinetic energy ; 

 or it may be the energy of electric charges at rest or in 

 motion ; or any one of the many kinds of potential 



