378 TENTH ANNUAL REPORT OP 



And if the resistance of the inserted liquid be computed in exactly the 

 same manner as that of the wire, we should get 



-J^ = 0.425, hence x = 0.5. 

 1 -j- ^ 



If the electrodes were removed 8 times as far apart, other things re- 

 maining the same, we should expect, if Ohm's law could be applied 

 without further trouble, that the stratum of liquid 8 times as thick 

 would oppose a resistance 8 times as great, and that the force of the 

 current should now be 



E _ 0.648 _ 0.648 _ ^ , ^n 



l + 8a;~l-f8x0.5"" 5 ~ 



But experiment gave in this case the force 0.199. 



At 12 times the distance apart of the pole plates, we should expect, 

 from the application of Ohm's law, that the current would be 0.0648, 

 "while experiment gave 0.120. 



In somewhat different form a similar result was obtained from the 

 experiments of Horsford, (Pog. Ann. LXX, p. 238.) In the circuit 

 of a Bunsen battery, he inserted a tangent compass and a rheostat. 

 By means of the latter the deflection of the needle was brought back 

 to 10°. A stratum of dilute sulphuric acid 2.5 centimetres thick, be- 

 tween two platinum plates, was now inserted, and with this 32 coils 

 were taken from the rheostat, or, in other words, 32 coils were removed 

 from the circuit to bring the deflection again to 10°. When the two 

 plates were placed twice as far apart, it was not necessary to remove 

 32 coils from the circuit to bring the needle to rest at 10°, but only 

 20.5 coils. For each increase in thickness of the fluid strata, of 2.5 

 millimetres, only 20.5 coils had to be removed from the circuit to 

 obtain the same deflection. 



Thus it appears, from all experiments of the kind, that the diminu- 

 tion of the strength of the current, which is i>roduced by inserting a 

 decomposing cell in the conducting circuit of a battery, does not 

 depend entirely upon the proper resistance of the liquid, but that there 

 is another cause at work diminishing the current, which, however, is 

 not augmented by the thickness of the stratum, but apparently is in- 

 dependent of it. 



Fechner ascribes this to the so-called '''resistance to transition," 

 which acts at the surface of contact between the metal plates and 

 liquid. Thus he imagines that the current has to overcome, besides the 

 resistance of the fluid itself, a j^eculiar resistance at the pole plates of 

 the decomposing cells, which we will denote by u. If, with a given 

 thickness of the liquid stratum, the strength of current is 



s= J= , (1) 



then for a stratum n times as thick, the strength of the current, ac- 

 cording to Fechner's view, will be 



S' =z p-r-^x • (2) 



il -f- It -\- n to 



Poggendorfi' at first defended this hypothesis of Fechner. Lenz 



