350 



ELECTROKINETICS. 



[PT. II. CH. VIII. 



ducing current from a battery to it by various electrodes, and 

 finding by touching the surface with two sharp conducting points 

 connected with a galvanometer, the locus of points of equal 

 potential. Doing the same for any other surface with the same 

 number of electrodes of the same sign will give a conformal trans- 

 formation of the two surfaces*. If the whole of one surface is 

 transformed upon only a part of the other, it is necessary to cut 

 out corresponding parts of the two surfaces, making the whole of 

 each equipotential edge an electrode. This can be done in practice 

 by soldering the edge of the sheet to a massive three-dimensional 

 conductor of great conductivity. Fig. 71 represents the flow in a 

 spherical sheet corresponding by Mercator's projection to the flow 

 in a plane sheet given in Fig. 22, and Fig. 47 represents Fig. 23 

 transformed to the sphere by stereographic projection. 



FIG. 71. 



* Kirehhoff. "Ueber die stationaren elektrischen Stromungen in einer ge- 

 krummten leitenden Flache." Monatsber. der BerL Akad. 1875. Ges. Abh. p. 56. 

 Kelvin. " Generalisation of Mercator's Projection performed by aid of Electrical 

 Instruments." Electrician, p. 553, 1892. 



