LIVING TORPEDOS IN BERLIN. 455 



ventral surfaces rested upon metallic non-polarisable electrodes, 

 with which the ends both of the battery circuit and of the gal- 

 vanometer circuit were in connection. See Fig. 18, A and B, which 

 represents the state of things for the homodromous and hetero- 

 dromous currents respectively. The battery circuit with the battery 

 are indicated by 2, the galvanometer by (P), the galvanometer 

 through which the branch is led off by (S). The branches of current 

 which proceed from the battery are indicated by unbroken arrows, 

 those of the absolutely positive polarisation by broken arrows, and 

 those of the relatively negative polarisation by dotted arrows. It 

 is unnecessary to remark that in this rough sketch we take no 

 account either of the duration of polarisation, or of induction. 



Fig. 1 8. 



Let E be the electromotive force of the battery : I, the resistance 

 of the battery circuit containing the battery and the galvanometer 

 (P) ; A., the resistance of the galvanometer circuit containing the 

 galvanometer (S) ; w, w ', the resistance of the preparation when the 

 current is homodromous or heterodromous respectively ; K, the sum 

 of the products wl+wX + Xl with the homodromous current, 

 according to Kirchoff ; K', the corresponding sum with the hetero- 

 dromous current. Let P be the constant by which the current 

 density prevailing in the preparation must be multiplied in order 

 to give the electromotive force of the homodromous absolutely and 

 relatively positive polarisation ; II, the corresponding constant for 

 the relatively negative polarisation ; /, the strength of the homo- 

 dromous current in the battery circuit ; 1\ that of the hetero- 

 dromous ; i t and *', the corresponding strengths of current in the 

 circuit derived through the galvanometer. 



In the battery circuit there prevails a current strength of 

 E (w -f A)/ which is due to the electromotive force of the battery. 

 To this is added whatever amount of current exists in the battery 

 circuit in consequence of the polarisations. The battery circuit has 



