and used in 1859, published in 1880. 
Fig. 10,—Sir William Thomson's Compensation arrangement for measuring Volta-force in Air and Gases by a null method, devised 
172 Prof. Oliver Lodge on the Seat of the 
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The upper plate of the condenser is uninsulated, and slides u 
p and down from one fiftieth to a quarter or half an inch from the lower 
the position of the slide being adjusted till no deflection ensues. © 
ed to the electrometer. The upper plate is put in communication with the lower one 
and is then raised, 
ated plate, which is permanently join 
momentarily through the,slide resistance, 
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