BRIDGMAN. — THE ELECTROSTATIC FIELD. 



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being positive to the right, negative to the left. <£ has now become 

 discontinuous, it has the negative of its old values below the X axis. 

 We have now found the potential and force functions due to an infinite 

 conducting plane, with a strip two units wide removed, one half charged 

 positively and the other negatively to the same density. This may be 

 called the hyperbolic element, since the equipotential surfaces are 

 hyperbolic cylinders. 



Figure 6. 



The figures illustrate all possible combinations of two elliptic or hyper- 

 bolic elements, the centres being unit distance apart and the direction of 

 one perpendicular to that of the other. 



Figure 1 shows two elliptic elements charged with electricity of the 

 same sign. It is to be noticed that the elements are no longer equi- 

 potential ; that is, they can no longer be regarded as conducting. We 

 must think of the charges as rigidly attached to the boards in the position 



