Prof. Faraday on the Conservation of Force. 233 



contrast with the assumed variable condition of the gravitating 

 force supposed to reside in the particles of matter. 



Even gravity itself furnishes the strictest proof of the conser- 

 vation of force in this, that its power is unchangeable for the 

 same distance ; and is by that in striking contrast with the varia- 

 tion which we assume in regard to the cause of gravit]/, to account 

 for the results at different distances. 



It will not be imagined for a moment that I am opposed to 

 what may be called the law of gravitating action, that is, the law 

 by which all the known effects of gravity are governed ; what I 

 am considering, is the definition of the force of gravitation. 

 That the result of one exercise of a power may be inversely as 

 the square of the distance, I believe and admit ; and I know that 

 it is so in the case of gravity, and has been verified to an extent 

 that could hardly have been within the conception even of Newton 

 himself when he gave utterance to the law ; but that the totality 

 of a force can be employed according to that law I do not believe, 

 either in relation to gravitation, or electricity, or magnetism, or 

 any other supposed form of power. 



I might have drawn reasons for urging a continual recollection 

 of, and reference to, the principle of the conservation of force 

 from other forms of power than that of gravitation ; but I think 

 that when founded on gravitating pheeuomena, they appear in 

 their greatest simplicity; and precisely for this reason, that gra- 

 vitation has not yet been connected by any degree of converti- 

 bility with the other forms of force. If I refer for a few minutes 

 to these other forms, it is only to point, in their variations, to the 

 proofs of the value of the principle laid down, the consistency of 

 the known pha^nomena with it, and the suggestions of research 

 and discovery which arise from it*. Heat, for instance, is a mighty 

 form of power, and its effects have been greatly developed; 

 therefore assumptions regarding its nature become useful and 

 necessary, and philosophers try to define it. The most probable 

 assumption is, that it is a motion of the particles of matter; but 

 a view, at one time very popular, is, that it consists of a particular 

 fluid of heat. Whether it be viewed in one way or the other, the 

 principle of conservation is admitted, I believe, with all its force. 

 When transferred from one portion to another portion of like 

 matter, the full amount of heat appears. When transferred to 

 matter of another kind, an apparent excess or deficiency often 

 results ; the word " capacity " is then introduced, which, whilst 

 it acknowledges the principle of conservation, leaves space for 

 research. When employed in changing the state of bodies, the 

 appearance and disappearance of the heat is provided for con- 



* Iltlmlioltz, " On the Conservation of Force," Taylor's Scientific Me- 

 moirs, 2nd series, )85c(, p. 114. 



