Theories of Electricity 133 



" It is supposed that all kinds of common matter do 

 not attract and retain the electrical with equal strength 

 and force for reasons to be given hereafter. And that 

 those called electrics per se, as glass, etc., attract and 

 retain its strongest and contain the greatest quantity. 



" We know that the electrical fluid is in common 

 matter, because we can pump it out by the globe or 

 tube. We know that common matter has near as much 

 as it can contain, because, when we add a little more to 

 any portion of it, the additional quantity does not enter 

 but forms an electrical atmosphere. And we know that 

 common matter has not (generally) more than it can 

 contain, otherwise all loose portions of it would repel 

 each other, as they constantly do when they have electric 

 atmospheres." 



The conception of Franklin that electricity was an 

 indestructible and subtile fluid which permeated all 

 bodies was a not unnatural one to occur to a philosopher 

 of that time, for it was the century in which the notion 

 of material fluids was invented to explain diverse phys- 

 ical phenomena, for example, heat and magnetism. But 

 the great merit of Franklin lies in the explanation of 

 positive and negative electricity by means of a single 

 fluid. Every unelectrified body is supposed to contain 

 its normal quantum of this electrical fluid. A body is 

 positively electrified when it contains an excess of this 



