450 



LIVING TOBPEDOS IN BERLIN. 



In accordance with the reality it is seen that at first both 

 currents give absolutely positive polarisation (section i of the 

 figure), the homodromous being the stronger. Then comes a period 

 (section 2) in which, although both polarisations are still absolutely 

 positive, the heterodromous is the stronger. In section 3 the 

 homodromous polarisation is seen to be absolutely negative and 

 distinctly smaller than the heterodromous. In section 4 the two 

 polarisations approach equality. 



I need scarcely point out that it was the phenomenon of section 

 3 which Sachs had seen, without having been aware of the two 

 preceding, and which he described in words which from their 

 apparent contradiction to my results caused me so much difficulty, 

 viz. that ' relatively negative polarisation is always stronger in 

 the direction of the shock.' There still remains however some 



Fig. 17. 



obscurity. Besides the polarisation experiments thus explained, 

 Sachs has given others which are shown graphically in Plate II of 

 the book on Gymnotus. In these experiments also polarisation by 

 either current was without exception first relatively negative, but 

 so strongly that the mirror shot out to the equator, in returning 

 from which, according to Sachs' description, it swung several times 

 on either side of the zero point. If the closing time exceeded a 

 certain duration it swung twice over the zero point into the 



