12 ANIMAL MECHANISM. 



intensity of the light diminish, and the decomposition of 

 the water in the voltameter grow less. All these phenomena 

 resume their pristine energy as soon as we suppress the 

 production of mechanical action. 



During this time, all the force expended in these various 

 forms of apparatus is disengaged from the battery under the 

 influence of a chemical action: the transformation of a certain 

 quantity of zinc into sulphate of zinc. Thus, in the furnace 

 of a steam engine, the combustion of the coal, that is to say, 

 the oxidation which transforms carbon into carbonic acid 

 disengages heat, which is afterwards converted into work. 



But this force, disengaged from bodies, was contained in 

 them when the zinc was in the condition of metal, and the 

 carbon in the state of coal; these bodies had employed in 

 their formation the same quantity of force which they 

 have yielded up in passing into another condition. Tims it 

 would be necessary to restore to the sulphate of zinc and to 

 the carbonic acid as much electricity or heat as they have 

 thrown out, in order to reproduce the metallic zinc or the 

 carbon in a pure state. 



According to the modern theory, force which manifests 

 itself at a given moment is not created, but only rendered 

 sensible, from being latent. 



Here in tension is that potential force, which, stored up in 

 a body, waits the opportunity to manifest itself. Thus a 

 sti-etchcd spring will at the end of an indefinite time give back 

 the force which has been used to stretch it ; and a weight, 

 lifted to a certain height, will restore, the instant it fulls, 

 the work that has been employed upon raising it. 



