234 Prof. Faraday on the Consei'vation of Force. 



sisteutly by the assumption of enlarged or diminislied motion, or 

 else space is left by the term " capacity " for the partial views 

 which remain to be developed. When converted into mechanical 

 force, in the steam- or air-engine, and so brought into direct 

 contact with gravity, being then easily placed in relation to it, 

 still the conservation of force is fully respected and wonderfully 

 sustained. The constant amount of heat developed in the whole 

 of a voltaic current described by M. P. A. Favre*, and the pre- 

 sent state of the knowledge of thermo-electricity, are again fine 

 partial or subordinate illustrations of the principle of conserva- 

 tion. Even when rendered radiant, and for the time giving no 

 trace or signs of ordinary heat action, the assumptions regarding 

 its nature have provided for the belief in the conservation of 

 force, by admitting either that it throws the sether into an equi- 

 valent state, in sustaining which for the time the power is en- 

 gaged, or else that the motion of the particles of heat is em- 

 ployed altogether in their own transit from place to place. 



It is true that heat often becomes evident or insensible in a 

 manner unknown to us ; and we have a right to ask what is 

 happening when the heat disappears in one part, as of the 

 thermo-voltaic current, and appears in another ; or when it en- 

 larges or changes the state of bodies ; or Avhat would happen, if 

 the heat being presented, such changes were purposely opposed. 

 AVe have a right to ask these questions, but not to ignore or 

 deny the conservation of force ; and one of the highest uses of 

 the principle is to suggest such inquiries. Explications of similar 

 points are continually produced, and will be most abundant from 

 the hands of those who, not desiring to ease their labour by 

 forgetting the principle, are ready to admit it either tacitly, or 

 better still, effectively, being then continually guided by it. Such 

 philosophers believe that heat must do its equivalent of work : 

 that if in doing work it seem to disappear, it is still producing 

 its equivalent effect, though often in a manner partially or totally 

 unknown ; and that if it give rise to another form of force (as 

 we imperfectly express it), that force is equivalent in power to 

 the heat which has disappeared. 



What is called chemical atiractiun affords equally instructive 

 and suggestive considerations in relation to the principle of the 

 conservation of force. The indesti-uctibility of individual matter 

 is one case, and a most important one, of the conservation of 

 chemical force. A molecule has been endowed with powers 

 which give rise in it to various qualities ; and these never change, 

 either in their nature or amount. A particle of oxygen is ever 

 a particle of oxygen — nothing can in the least wear it. If it 

 enters into combination and disappears as oxygen, — if it pass 

 * Comptes Rendus, 1854, vol. xxxix. p. 1212. 



