22O "Journal of Experiments, 1771 



equivalent to drawing out wire 20 inches, which is supposed = 4-54 inches of 

 air, which is as near an agreement as can be expected. 



By a medium of the experiments, the plate of air -39 thick required wire 

 to be drawn out n inches less than A and B, the different experiments varying 

 from 9 to 14, therefore the plate of air contains 2-6 inches more electricity 

 than A and B, id est, it contains 39-3 inches of electricity. The plate of air 

 '343 seemed by i experiment to contain 42-7 of electricity. 



Therefore plate of air -39 contains 4-94 times more electricity than a circle 

 of same diameter, therefore quantity of electricity therein is to that in circle 

 of same diameter as radius to thickness x 2-06 or quantity of electricity = com- 

 puted power x -243. 



459] Four irregular pieces of glass, N, O, P, Q, were coated with circles. 

 The thickness, specific gravity of glass and diameter of circles are marked in 

 [Art. 370], the thickness of glass being found by taking thickness with calipers 

 at center of proposed circle, and finding a part of outside of same thickness 

 and measuring that part by Bird's instrument*; the computed power of all 

 being just 40. The experiments were tried with sliding wire as former[ly]. 



Tried with large trial plate. 



With small trial plates. 



N . + 9 se P- P os - 



+ 6 did not. 



Q +o sep. considerably. 



O + o sep. considerably, but not so much as Q. 



P +6 doubtful. 



+ 9 sep. plainly. 



The afternoon when these were tried, hygrometer corks closed in about 

 20 seconds. 



The trial plates being inlarged, tried with large trial plate. 

 P +42 doubtful. 



+ 39 do. 

 + 24 sep. 

 + 28 doubtful. 



O + o very little, rather doubtful. 



Q + o did not sep. 



N +21 sep. a little. 



P +24 sep. a little. 



* [Arts. 341, 517.] 



