212 HISTORY OF ELECTRICITY. 



lombian theory. Ho finds that, from the supposition of a fluid and of 

 particles of matter exercising such forces as that theory assumes (with 

 the very allowable additional supposition that the particles are small 

 compared with their distances), it follows that the particles would, ex- 

 ert a force, repulsive at the smallest distances, a little further on van- 

 ishing, afterwards attractive, and at all sensible distances attracting in 

 proportion to the inverse square of the distance. Thus there would 

 be a position of stable equilibrium for the particles at a very small 

 distance from each other, which may be, M. Mosotti suggests, that 

 equilibrium on which their physical structure depends. According to 

 this view, the resistance of bodies to compression and to extension, as 

 well as the phenomena of statical electricity and the mutual gravita- 

 tion of matter, are accounted for by the same hypothesis of a single 

 fluid or ether. A theory which offers a prospect of such a generali- 

 zation is worth, attention ; but a very clear and comprehensive view 

 of the doctrines of several sciences is requisite to prepare us to esti- 

 mate its value and probable success. 



Question of the Material Reality of the Electric Fluid. At first 

 sight the beautiful accordance of the experiments with calculations 

 founded upon the attractions and repulsions of the two hypothetical 

 fluids, persuade us that the hypotheses must be the real state of things. 

 But we have already learned that we must not trust to such evidence 

 too readily. It is a curious instance of the mutual influence of the 

 histories of two provinces of science, but I think it willbe allowed to 

 be just, to say that the discovery of the polarization of heat has done 

 much to shake the theory of the electric fluids as a physical real it}'. 

 For the doctrine of a material caloric appeared to be* proved (from the 

 laws of conduction and radiation) by the same kind of mathematical 

 evidence (the agreement of laws respecting the elementary actions with 

 those of fluids), which we have for the doctrine of material electricity. 

 Yet we now seem to see that heat cannot be matter, since its rays 

 have sides, in a manner in which a stream of particles of matter can- 

 not have sides without inadmissible hypotheses. "We see, then, that 

 it will not be contrary to precedent, if our electrical theory, repre- 

 senting with perfect accuracy the laies of the actions, in all their 

 forms, simple and complex, should yet be fallacious as a view of the 

 cause of the actions. 



Any true view of electricity must include, or at least be consistent 

 with, the .other classes of the phenomena, as well as this statical elec- 

 trical action ; such as the conditions of excitation and retention of 



