1 1 4 Thoughts concerning Electricity 



It may also happen that the second body shall be made undercharged 

 though it is positively electrified, provided it be much less electrified than 

 the first body, and that the two bodies be placed near enough to each 

 other. 



207] The shock produced by making a communication between the 

 two surfaces of the Leyden vial seems owing only to the glass prepared 

 in that manner containing vastly more electricity on its positive side than 

 an equal surface of metal equally electrified, and vastly less on its negative 

 side than the same surface of metal negatively electrified to the same 

 degree, so that if two magazines of electricity were prepared, each able 

 to receive as much additional electricity by the same degree of electrifi- 

 cation as one of the surfaces of a Leyden vial, and one of the magazines 

 was to be positively electrified and the other negatively, there is no doubt 

 but what as great a shock would be produced by making a communication 

 between the two magazines as between the two surfaces of the Leyden 

 vial. 



I think, therefore, that the phenomena of the Leyden vial may very 

 well be accounted for on the principle of the 6th Corollary, for in the 

 Leyden vial the two surfaces of the glass are so near together, that the 

 electric matter on one surface may act with great force on that on the 

 other, and yet the electricity cannot jump from one surface to the other, 

 by which means perhaps the positive side may be made many times more 

 overcharged, and the negative side many times more undercharged, than 

 it would otherwise be. 



208] HYP. 5th. It seems reasonable to suppose that when the electric 

 fluid within any body is more compressed than it is in the air surrounding 

 it, it will run out of that body, and when it is less compressed it will run 

 into the body. 



COR. I. Let the body A , not electrified, be perfectly insulated, and let 

 an overcharged body be brought near it. The body A will thereby be 

 rendered less capable of containing electricity, and therefore the electric 

 fluid within it, as it cannot escape, will be rendered more compressed. 

 But the electricity in the adjoining air will, for the same reason, be also 

 compressed, and in all probability equally so, therefore the electricity will 

 have no disposition either to run in or out of the body. 



COR. II. It is evidently the same thing whether A be insulated, or 

 whether it be not insulated, but electrified in such manner that the fluid 

 within it be as much compressed as it was before by virtue of the insula- 

 tion. Therefore if the body A be now not insulated, but positively 

 electrified, and an overcharged body be brought to such a distance from 

 it that the electric fluid in the adjacent air be equally compressed with 

 that in A, such a quantity of electricity will thereby be driven out of A 

 that it will retain only its natural quantity. So that A will be neither 



