prior to the Introduction of the Potentials. 45 



nated with a star or globule, while the point which is near the 

 outer coating is illuminated with a pencil of rays; which 

 suggested to Franklin that the electric fluid, going from the 

 inside to the outside of the jar, enters at the former point and 

 issues from the latter. And yet again, in some cases the flame 

 of a wax taper is blown away from a brass ball which is 

 discharging vitreous electricity, and towards one which is 

 discharging resinous electricity. But Franklin remarks that 

 the interpretation of these observations is somewhat conjectural, 

 and that whether vitreous or resinous electricity is the actual 

 electric fluid is not certainly known. 



Regarding the physical nature of electricity, Franklin held 

 much the same ideas as his contemporaries ; he pictured it as 

 an elastic* fluid, consisting of " particles extremely subtile, since 

 it can permeate common matter, even the densest metals, with 

 such ease and freedom as not to receive any perceptible 

 resistance." He departed, however, to some extent from the 

 conceptions of his predecessors, who were accustomed to ascribe 

 all electrical repulsions to the diffusion of effluvia from the 

 excited electric to the body acted on ; so that the tickling 

 sensation which is experienced when a charged body is brought 

 near to the human face was attributed to a direct action of the 

 effluvia on the skin. This doctrine, which, as we shall see, 

 practically ended with Franklin, bears a suggestive resemblance 

 to that which nearly a century later was introduced by 

 Faraday ; both explained electrical phenomena without intro- 

 ducing action at a distance, by supposing that something which 

 forms an essential part of the electrified system is present at 

 the spot where any electric action takes place ; but in the older 

 theory this something was identified with the electric fluid 

 itself, while in the modern view it is identified with a state of 

 stress in the aether. In the interval between the fall of one 

 school and the rise of the other, the theory of action at a 

 distance was dominant. 



The germs of the last-mentioned theory may be found in 



*i.c., repulsive of its own particles. 



