530 



LIVING TORPEDOS IN BERLIN. 



lateral surface, re-enter it below the transverse median plane, and the 

 curves starting 1 from points of the dorsal surface, enter at cor- 

 responding points of the ventral surface. The prolongation of the 

 axis is a current curve which loses itself in infinity. In the 

 interior of the column, currents flow from the belly to the back, 



Fig. 23. 



those near the axis being- nearly parallel to it, those nearer the 

 lateral surfaces, diverging from each other, so that the curves cut 

 the lateral surfaces. To the left of the figure, distorted for a reason to 

 be mentioned immediately, the diagram represents the intersection 

 of the outer system of curves with the transverse plane of the fish 

 round a single column supposed to be active. 



If we imagine in the unlimited conducting mass, a second exactly 

 similar column by the side of the first column, its axis parallel to 

 that of the first, its dorsal and ventral surface in the same plane, so 

 that the transverse median planes belonging to both columns would 

 coincide, then the second column fills space with a system of curves 

 precisely similar to the first. The current threads belonging to 

 both the systems, compound themselves in any element of surface 

 whatever of space, according to the parallelepiped of forces, in con- 

 formity with the principle of superposition of currents J . The case 

 is precisely similar as regards a third, a fourth, or an n ih column. 

 If the distances of the columns from each other and their mass 



1 Comp. Helmholtz in PoggendorflTs Annalen, 1853, vol. Ixxxix. p. 212 f. 



