476 On a Case of Work produced by the Electric Current. 



degree ; it is therefore not surprising that the deviations of 

 the galvanometer, calculated on the basis of the real value of 

 the resistance of the circuit alone, should be less, when, besides 

 this real resistance, one must take into account a very con- 

 siderable fictitious resistance. 



This circumstance not having attracted my attention at the 

 commencement of the experiments, I cannot present the data 

 necessary for calculating the value of this fictitious resistance 

 in the experiments with nitrate of silver. For those with 

 iodide of cadmium (Table IV.) I determined this resistance 

 by measuring the intensity of the current, first, when the tube 

 and the galvanometer alone formed the circuit, and again 

 after the introduction of a coil of 7976 Siemens's units. I 

 found that the total resistance of the circuit was 18,240 

 units, while the real resistance was only about 5600. The 

 galvanometer-deviation A— D, calculated with this new 

 datum, was found to be 6* 6, in complete accordance with 

 the experiments. 



The electromotive force e, tending to produce a current 

 directed invariably downward in a column of nitrate of silver, 

 and upward in iodide of cadmium, is independent of the in- 

 tensity and direction of the current of the pile. I endeavoured 

 to pass through my tubes filled with nitrate of silver equal 

 currents alternately in opposite directions, supplied by a 

 magnetoelectric machine. These currents, without acting 

 themselves on the galvanometer, were to call forth the electro- 

 motive force e, which was to deflect the needles. 



Contrary to expectation, the experiment gave a negative 

 result ; the phenomena were the same as if the alternate cur- 

 rents had not traversed the liquid at all. The reader is re- 

 ferred for fuller details to the articles above mentioned. There 

 is reason to think that the quantity of electricity (necessarily 

 finite) conveyed by any induced current is insufficient to 

 charge the electrodes to a difference of potential above the 

 maximum electromotive force of polarization, as, according 

 to Mr. Varley* and Helmholtz, the electrodes may be re- 

 garded as the armatures of a condenser of enormous capacity. 

 Now, under these circumstances, although the true electro- 

 motive force of the induced current may at every instant be 

 superior to the maximum of polarization, the current cannot 

 pass through the liquid. This complex and little-studied 

 subject requires fresh researches for its complete elucidation. 



In the phenomena known under the name of " electrical 



* Philosophical Transactions, vol. clxi. p. 129 (1871). 



