250 ESSAYS OF A BIOLOGIST 



air and the air itself, precious stones and common 

 clay — ^all can be resolved into a limited number of 

 elements. And these elements in their turn can be 

 resolved into combinations, differing, it appears, only 

 quantitatively from each other, of electrical charges ; 

 so that at the last all matter is one, and becomes perhaps 

 indistinguishable, or at least inseparable, from energy. 

 There is no personal operator for particular happenings ; 

 the lightning and the volcano are the inevitable out- 

 come of the material constitution of things, equally 

 with the form and colour of a pebble and with the 

 fact that it will drop to the ground if it is let fall. 

 All is impersonal order and unity. 



There is, however, one other great fact about the 

 system of inorganic matter. The energy contained 

 in it tends to be degraded, as the physicists say — in 

 other words, to become less readily available. There 

 is available energy in moving matter. There is 

 potential energy in all matter, dependent upon whether 

 it can be set in motion. But if the sea were to cover 

 the whole surfece of the globe, it would be impossible 

 to extract energy from running water as we do now, 

 because no water would be running. So too heat 

 is energy ; but it is only available when it can flow, 

 wiien there are hotter and colder bodies. The law 

 under which transformations of energy operate has 

 now been investigated, and it has been established 

 that in every energy-transaction a certain modicum 

 goes to waste as unavailable heat, so that, unless some 



