Vieisosqfthe Theory of Galvanism. 163 



effect upon the needle; but on removing any pair of the water- 

 cells from the circuit and replacing them there, the equili- 

 brium was disturbed in favour of the acid system. But what 

 seems to me to be still more remarkable, is the fact, that the 

 same effect, only on a smaller scale, was obtained by making 

 any pair belonging to the water system alternately rise and 

 sink a little without removing it entirely from the circuit. 

 Another fact worthy of being stated is, that immediately after 

 the equilibrium had been disturbed, opening and closing 

 the circuit by the galvanometer, or by any pair of the acid 

 system, causes a similar effect, that is to say, a perceptible in- 

 crease of the acid current. The arrangement left to itself 

 closed regains, however, its previous condition within a very 

 short space of time, i. e. assumes such a state of current equi- 

 librium as can only be changed again by breaking and re- 

 establishing the circuit by a pair belonging to the water system. 

 It is also worthy of remark, that the magnitude of the differ- 

 ences of currents obtained by the means mentioned is variable. 

 I have repeated the same experiment over and over again, and 

 at each time I got a fresh result as to the number of degrees 

 of the needle's deviation ; sometimes even, no deviation at all 

 took place. On making use of an aqueous acid fluid con- 

 taining 1 part of sulphuric acid in one system of the cells, 

 whilst there was common water in the other, I obtained a 

 deviation in favour of the acid current which amounted to 

 about 90° : in a very short time the needle, however, returned 

 to zero. A fluid containing li, 2, 2i, 3, 3|, 4, 4i, 5 parts 

 of acid did not affect the needle ; from 5^ — 8 parts produced a 

 temporary deviation of about 40° in favour of the water cur- 

 rent ; from 9 — 1 1 parts had no effect ; 1 5 parts caused a consi- 

 derable deviation in favour of the acid current, but lasted only 

 for a few moments ; 20 parts caused no effect upon the needle. 

 3. A liquid containing for 100 parts of water 1 — 10 parts 

 of common muriatic acid, and used in one system of the cells, 

 did not cau-e any deviation; 15 parts caused a deviation of 

 the needle of 40° in favour of the water current : after a short 

 time the former returned to zero, but was again made to de- 

 viate in the same manner as it was at first. This change of 

 equilibrium into difference of currents, and vice versa, took 

 place several times. From 20 — 25 parts of acid caused a devia- 

 tion of about 45° in favour of the water current, which lasted 

 rather a long time ; 30 parts of acid made the needle turn 

 round its central point several times in such a direction as to 

 indicate the prevalence of the water current. The same ex- 

 periment made another time showed no difference of cur- 

 rents, the needle remaining at zero. 



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