390 Intelligence and Miscellaneous Articles. 



In the second part he shows, also experimentally, that two currents, 

 proceeding from the same pile and travelling together in a liquid, 

 exercise an influence on each other, both becoming weaker, and 

 that no such influence is exerted between two currents furnished by 

 independent piles — an important fact, which offers a strong analogy 

 to the phenomena of the interference of light, and appears to merit 

 further investigation. 



Fechner and Matteucci experimented upon the resistance of liquids 

 to electric currents, but in an incomplete manner and with inexact 

 means of measurement ; so that the results obtained by them cannot 

 be considered accurate ; and they are at variance in some cases with 

 those given by Dr. Macaluso. 



The method followed by the author is similar to that adopted by 

 Becquerel in his researches on the electric conductivity of liquids ; 

 but he uses an indicating instrument very much more sensitive and 

 accurate than that of Becquerel — that is, a Weidmann's reflecting 

 galvanometer. He divides the current furnished by the pile into 

 two portions, passing in contrary directions through the two coils of 

 the galvanometer, and regulates the resistance so as to maintain the 

 mirror on the zero of the scale. One of the two circuits is kept con- 

 stant ; the other is variable, and comprehends the liquid and various 

 resistance coils, previously compared with one another and graduated 

 to a common scale. In experimenting, the apparatus was arranged 

 so that the mirror of the galvanometer stood at zero when the liquid 

 resistance was entirely removed by placing the electrodes in contact : 

 the liquid was then interposed, with various lengths and various 

 transverse areas ; the mirror of course moved from its zero position, 

 and in order to bring it back a portion of the resistance of the coils 

 had to be removed ; this portion of resistance removed was equal to 

 that opposed by the liquid in the circumstances of the experiment. 

 With a view to simplifying the conditions, he adopted as electrodes 

 plates having only one face metallic and naked, the remaining sur- 

 faces being varnished ; they were of copper, and the liquid adopted 

 was a solution of sulphate of copper. 



The length of the liquid conductor was varied by placing the 

 electrodes at different distances apart ; and its transverse section was 

 narrowed or widened by means of glass plates placed in a series of 

 grooves made in the bottom and sides of the trough containing the 

 liquid, so as to form a channel of various cross section between the 

 two electrodes. 



The author also experimented upon the case of the two electrodes 

 having different widths. And he gives Tables of the resistance op- 

 posed by the conducting liquid in the various circumstances ; which 

 resistance he has also expressed by means of curves, in which the di- 

 mensions of the liquid section are represented by the abscissae, the 

 resistances by the ordinates. He arrives at the following conclusions. 

 1. Even when the electrode has only one face in metallic contact 

 with the liquid, the electrical resistance of the liquid depends not 

 only upon the dimensions of the electrodes, but also upon the section 

 of the liquid itself at the sides of the electrodes. 



