184 ANNUAL OF SCIENTIFIC DISCOVERY. 



in this, that its power is unchangeable for the same distance ; and is by that 

 in striking contrast with the variation which we assume in regard to the cause 

 of gravity, 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 arc 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 phenomena, they appear in their greatest simplicity; and pre- 

 cisely for this reason, that gravitation has not yet been connected by any de- 

 gree of convertibility 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 

 phenomena 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 viowed in one way or the other, the principle of con- 

 servation is admitted, I believe, with all its force. When transferred from 

 one portion to another portion of like matter, the full amount of heat ap- 

 pears. When transferred to matter of another kind an apparent excess or 

 deficiency often results; the word "capacity "is then introduced, which, 

 while it acknowledges the principle of conservation, leaves space for re- 

 search. When employed in changing the state of bodies, the appearance 

 and disappearance of the heat is provided for consistently by the assumption 

 of enlarged or diminished motion, or else space is left by the term " capa- 

 city " 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 witli gravity, being then easily placed in relation to it, still the con- 

 servation of force is fully respected and wonderfully sustained. The con- 

 stant amount of heat developed in the whole of a voltaic current described 

 by M. P. Favre,t and the present state of the knowledge of thermo-electric- 

 ity, are again fine, partial or subordinate illustrations of the principles of 



Helmlioltz, on the Conservation of Force. Taylor's Scientific Memoirs, Second 

 Sesies, 1853, p. 114. 

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



