ELECTRICAL MEASUREMENT. 439 



globe by some imaginary means be capable of 

 becoming gradually diminished in its diameter. 

 Suppose, in the first place, the insulation to be 

 exceedingly perfect, and the resistance of the 

 conducting wire to be therefore enormously great, 

 so that in the course of a minute or two there 

 is but little loss of potential. Now let this 

 globe, which is supposed to be shrinkable or ex- 

 tendable at pleasure, be shrunk from the metre 

 radius to 90 centimetres radius, what will the 

 effect be? The effect will be that the potential 

 will increase in the ratio of 90 to 100. Shrink the 

 globe to half its dimensions the potential will be 

 double, and so on. That follows from the result 

 of the mathematical theory that the electrostatic 

 capacity of a globe is numerically equal to its 

 radius. Now, while the globe is charged, let its 

 radius be diminished and let it shrink at such a 

 speed that the potential shall remain constant. 

 There, then, you can imagine a globe losing a 

 constant quantity of electricity per unit of time, 

 because it is kept now at a constant potential, 

 and a globe kept by this wonderful shrinking 



