Prof. Faraday on the Conservation of Force. 237 



any case where the force remaining unchanged in form is altered 

 in direction only, to look for the new disposition of the force ; 

 as in the cases of magnetism, static electricity, and perhaps gra- 

 vity, and to ascertain that as a whole it remains unchanged in 

 amount : — or, if the original force disappear, either altogether or 

 in part, it will lead us to look for the new condition or form of 

 force which should result, and to develope its equivalency to the 

 force that has disappeared. Likewise, when force is developed, 

 it will cause us to consider the previously existing equivalent to 

 the force so appearing; and many such cases there are in che- 

 mical action. When force disappears, as in the electric or mag- 

 netic induction after more or less discharge, or that of gravity 

 with an increasing distance, it will suggest a research as to 

 whether the equivalent change is one within the apparently 

 acting bodies, or one external (in part) to them. It will also 

 raise up inquiry as to the nature of the internal or external state, 

 both before the change and after. If supposed to be external, 

 it will suggest the necessity of a physical process, by which the 

 power is communicated from body to body ; and in the case of 

 external action, will lead to the inquiry whether, in any case, 

 there can be truly action at a distance, or whether the jether or 

 some other medium is not necessarily present. 



We are not permitted as yet to see the nature of the source 

 of physical power, but we are allowed to see much of the con- 

 sistency existing amongst the various forms in which it is pre- 

 sented to us. Thus, if in static electricity we consider an act of 

 induction, we can perceive the consistency of all other like acts 

 of induction with it. If we then take an electric current and 

 compare it with this inductive effect, we see their relation and 

 consistency. In the same manner we have arrived at a know- 

 ledge of the consistency of magnetism with electricity, and also 

 of chemical action and of heat with all the former ; and if we see 

 not the consistency between gravitation with any of these forms 

 of force, I am strongly of the mind that it is because of our igno- 

 rance only. How imperfect would our idea of an electric cur- 

 rent now be if we were to leave out of sight its origin, its static 

 and dynamic induction, its magnetic influence, its chemical and 

 heating effects ? or our idea of any one of these results, if we left 

 any of the others unregarded? That there should be a power 

 of gravitation existing by itself, having no relation to the other 

 natural powers, and no respect to the law of the conservation of 

 force, is as little likely as that there should be a principle of 

 levity as well as of gravity. Gravity may be only the residual 

 part of the other forces of nature, as Mossotti has tried to show ; 

 but that it should fall out from the law of all other force, and 

 should be outside the reach either of further experiment or philo- 



