684 LECTURE IIV. 



imperfect state: we know little or nothing of the intimate nature of the 

 substances and actions concerned in it: and we can never foresee, without 

 previous experiment, where or how it will be excited. We are wholly igno- 

 rant of the constitution of bodies, by Avhich they become possessed of differ- 

 ent conducting powers; and we have only been able to draw some general 

 conclusions respecting the distribution and equilibrium of the supposed electric 

 fhiid, from the laws of the attractions and repulsions that it appears to exert. 

 There seems to be some reason to suspect, from the phenomena of cohesion 

 and repulsion, that the pressure of an elastic medium is concerned in the ori- 

 gin of these forces; and if such a medium really exists, it is perhaps nearly 

 related to the electric fluid. The identity of the general causes of electrical 

 and of galvanic effects is now doubted by few ; and in this country the prin- 

 cipal phenomena of galvanism are universally considered as depending on che- 

 mical changes; perhaps, also, time may show, that electricity is very materi- 

 ally concerned in the essential properties, which distinguish the different kinds 

 of natural bodies, as well as in those minute mechanical actions and affections 

 ■which are probably the foundation of all chemical operations ; but at present 

 it is scarcely safe to hazard a conjecture on a subject so obscure, although 

 Mr. Davy's experiments have already in some measure justified the boldness 

 of the suggestion. 



