210 HISTOEY OF ELECTRICITY. 



has recently 14 described some important experiments and measures ; 

 but his apparatus was of such a kind that the comparison of the results 

 with the Coulombian theory was not easy ; and indeed the mathema- 

 tical problems which Mr. Harris's combinations offered, require another 

 Poisson for their solution. Still the more obvious results are such as 

 agree with the theory, even in the cases in which their author con- 

 sidered them to be inexplicable. For example, he found that by 

 doubling the quantity of electricity of a conductor, it attracted a body 

 with four times the force ; but the body not being insulated, would 

 have its electricity also doubled by induction, and thus the fact was 

 what the theory required. 



Though it is thus highly probable that the Coulombian theory of 

 electricity (or the ./Epinian, which is mathematically equivalent) will 

 stand as a true representation of the law of the elementary actions, we 

 must yet allow that it has not received that complete evidence, by 

 means of experiments and calculations added to those of its founders, 

 which the precedents of other permanent sciences have led us to look 

 for. The experiments of Coulomb, which he used in the establishment 

 of the theory, were not very numerous, and they were limited to a 

 peculiar form of bodies, namely spheres. In order to form the proper 

 sequel to the promulgation of this theory, to give a full confirmation, 

 and to ensure its general reception, we ought to have experiments 

 more numerous and more varied (such as those of Mr. Harris are) shown 

 to agree in all respects with results calculated from the theory. This 

 \vould, as we have said, be a task of labor and difficulty ; but the per- 

 son who shall execute it will deserve to be considered as one of the 

 real founders of the true doctrine of electricity. To show that the 

 coincidence between theory and observation, which has already been 

 proved for spherical conductors, obtains also for bodies of other forms, 

 will be a step in electricity analogous to what was done in astronomy, 

 when it was shown that the law of gravitation applied to comets as 

 well as to planets. 



But although we consider the views of ^Epinus or Coulomb in a very 

 high degree probable as a formal theory, the question is very different 

 when we come to examine them as & physical theory that is, when 

 we inquire whether there really is a material electric fluid or fluids. 



Question of One or Two fluids. In the first place as to the qnes- 

 lion whether the fluids are one or two ; Coulomb's introduction of 



14 Phil. Trans. 1334, p. 2. 



