PROGRESS OF ELECTRICAL THEORY. 37 



experiments more numerous and more varied (such 

 as those of Mr. Harris are) shown to agree in ajl 

 respects with results calculated from the theory. 

 This would, as we have said, be a task of labour 

 and difficulty ; but the person 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 a 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 question whether the fluids are one 

 or two ; Coulomb's introduction of the hypothesis 

 of two fluids has been spoken of as a reform of the 

 theory of ^Epinus ; it would probably have been 

 more safe to have called his labours an advance 

 in the calculation, and in the comparison of hypo- 

 thesis with experiment, than to have used language 

 which implied that the question, between the rival 

 hypotheses of one or two fluids, could be treated 



