282 



"Journal of Experiments, Aug. 13, 1773 



The three last columns are the distances at which Lane's electrometer dis- 

 charged, expressed in divisions, or 6o th parts of a revolution of the screw. 



By p' ^ [Art. 551] the distance at which Lane's discharges is as the j 



power of the quantity of electricity in the jar, and the quantity of electricity 

 when the straw electrometer is at 2 + 3, id est the usual charge is to that when 



Henly's is at 90 as i to | ,_ j* . 



571] Comparison of Lane's electrometer with light straw electrometer in different 

 weather. 



Lane's electrometer was compared with the light straw electrometer by 

 the apparatus represented above. A being the globe, B a conductor, CD a wooden 

 rod supported on two waxed glass pillars, having a pin at D almost in contact 

 with the conductor, the straw electrometer being hung to C. is a jar with 

 Lane's electrometer fastened to it, supported on a bracket fixed to glass pillars, 

 the wire of which touches CD. 



The distance of C from the globe is 54^ inches and from the nearest glass 

 pillar 32 inches. The height of the pith balls above the floor is 36} inches. 



A small board with divisions on it, not represented in the figure, supported 

 on an upright wooden rod, is placed behind the straw electrometer 25 inches 

 from it, and a bit of tin with a narrow notch in it for an eye sight is placed at 

 the same distance before the electrometer. 



The outward divisions on the board, or those called the 4 th , are at 5 inches 

 asunder, the 3 r " at 4 inches, the 2 nd at 3 inches, and the I st at 2. 



As I found it impracticable looking attentively at both balls of the electro- 

 meter, I looked only at one, which, as my eye was guided by a narrow slit, was 

 sufficient, and when I had made the experiment looking at one ball I repeated 

 it looking at the other, so that the mean would be right though the slit was not 

 right placed. 



A wire was continued from the coating of the jar to the earth. 



