190 Repulsion with Different Degrees 



wires when used were just even with the bottom of the cork balls, and 

 were kept in that situation by wax, the wax being cut off even with the 

 bottom of the corks, so as to leave no roughnesses to carry off the electricity. 

 In like manner, when the wires were not used, the ends of the straws were 

 closed up with wax. 



388] The proportion which the force with which the balls of this 

 electrometer endeavoured to close when the wires were inserted bore to 

 that with which they endeavoured to close without the wires was thus 



(A 

 found. The weight of the straw \r> with its ball and centre pin but 



(7-6 

 without its wire was found to be V, , grains, and the distance of its 



center of gravity from the center of suspension was I inches, as was 



found by balancing it on the edge of a knife. Consequently the force with 

 which this straw, when put in its place, endeavours to descend towards 

 the perpendicular, supposing it to be removed to a given distance from 

 (7-6 x 5-36 



WaS as 0.65 x 5-285 ' 



The weight of the wire inserted was \ grains, and half its length 



was \ Z 2 ^ inches, so that as the distance of the bottom of the cork balls 

 (i-oo 



from the center of suspension was n-i inches, the distance of its center 

 of gravity from the center of suspension was j . inches, and therefore 



the excess of the force with which the ball endeavours to descend towards 

 the perpendicular when the wire is inserted above that with which it 

 endeavours to descend without [the wire] is to the force with which it 



(12-05 x 0-87 , [7-6 x 5-36 

 endeavours to descend without the wire as 4 y lfi.fi -ft-' 



2*Q2 



or as \ to one. Therefore the force with which the electrometer en- 

 (2'Oo 



deavours to close when the wires are inserted is to that with which it 

 endeavours to close without the wires as 3-9 to i. 



389] E and F are two coated Leyden vials, nearly of the same size. 

 The outside coatings of both communicate with the ground, and the 

 inside coating of E communicates with CD, but not that of F. 



390] The way in which I tried the experiment was as follows. I first 

 compared the electrometer C with the electrometer D without the wires, 

 and found that when the jar E was electrified to such a degree as to make 



D separate \ divisions, C separated \ \ divisions, so that the 



same 



