OPENING- OF NEW PROBLEMS. 375 



repeat the same observations nearly in regard to magnetism 

 whether to be assumed as a fluid, or two fluids or electric cur- 

 rents whether the external action be supposed to be action 

 at a distance, or dependent on an external condition and 

 lines of force still, all are intended to admit the conserva- 

 tion of power as a principle to which the phenomena are 

 subject. 



The principles of physical knowledge are now so far de- 

 veloped as to enable us not merely to define or describe the 

 known, but to state reasonable expectations regarding the 

 unknown ; and I think the principle of the conservation of 

 force may greatly aid experimental philosophers in that duty 

 to science, which consists in the enunciation of problems to 

 be solved. It will lead us, in any case where the force re- 

 maining 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 gravity, and to as- 

 certain 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 develop its equivalency to the 

 force that has disappeared. Likewise, when force is devel- 

 oped, it will cause us to consider the previously-existing equiv- 

 alent to the force so appearing ; and many such cases there 

 are in chemical action. When force disappears, as in the 

 electric or magnetic 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 



