

LIVING TORPEDOS IN BERLIN. 507 



a short (5), 



t 37 1 2 9 t 37 I 29 sc. 



If we take also the numbers of the tracts of medium length 

 (i, 2, 3), then we find, as a mean of all numbers in the same 

 category, the ratio of the homodromous to the heterodromous 



currents, in the long tract 



ioo : 39-1, 



in the medium-length tracts, 



ioo : 45-8, 

 in the short tract, 



ioo : 78-4; 



thus the longer the tract traversed, so much the greater is this 

 ratio. The following numbers, which afford one of the most striking 

 instances of irreciprocity, were obtained with the seventh torpedo 

 on the second day, with a short distance (not indicated) of the 

 galvanometer coil : 



Long tract. 

 t 217 | 28 t 160 | 30. 



Short tract, 

 t J 7<5 i 155 t 176 I 155- 



Long tract, 

 t 165 | 14 f 165 j 22. 



The ratio of the current strengths with the long tract is 



ioo : 13-3, 

 with the short, 



ioo : 88-1. 



One might object to this, that with a longer tract, the pre- 

 paration forms a greater part of the total resistance of the circuit, 

 and that this has misled us as regards the relation of greater 

 irreciprocity to greater length. The slight difference between the 

 homodromous current strength for long and short tracts shows that 

 the resistance of the preparation, unquestionable as it maybe in com- 

 parison with that of the clay points, forms a by no means large 

 proportion of the total resistance of the circuit. However, it is 

 desirable to establish safe from all doubt, a point so important as 

 that of the increase of irreciprocity with the length of the tract 

 traversed by the current. 



The idea that the irreciprocity of conduction is influenced by the 

 total resistance of the circuit, implies that it can be expressed by an 

 additive term in the denominator of the fraction which represents the 

 heterodromous current strength in Ohm's formula. Let us call this 



