4<66 Intelligence and Miscellaneous Articles. 



the latter the inducing force is independent of the nature of the metal, 

 the question arises, does this independence of the nature of the in- 

 duced conductor also extend to liquids, and therefore to all conduc- 

 tors ? Experiments on this point have not been made, so far as I am 

 aware. 



I made three experiments with three different arrangements, of 

 which I shall only communicate the most successful, as they all led 

 to the same result. 



In a metallic contact connected with the compass apiece of caout- 

 chouc tubing 179 centims. in length was inserted ; its external dia- 

 meter was 13 millims., its internal 7 millims. In both ends amal- 

 gamated zinc cylinders were firmly tied ; and the tubing was entirely 

 filled with saturated solution of zinc vitriol. The intensities of the 

 induced current werejnow to be compared according to whether the 

 liquid part, or a corresponding one of the metallic circuit, or both 

 simultaneously were exposed to inducing action. 



A powerful Ruhmkorff's electromagnet was used as inductor, of 

 the kind which serves for investigating the action on the plane of 

 polarization. The current was furnished by two adjacent series, 

 each of four Bunsen's elements. The two coils were provided with 

 cylindrical poles of 65 millims. diameter and plane faces, and were 

 so arranged that the two poles formed a cylinder between the 

 spirals 55 millims. in length. About these the caoutchouc tubing 

 was first of all coiled in six turns, then, in a further series of expe- 

 riments, simultaneously with it a part of the metallic conduction, also 

 in six turns, of approximately equal radius ; the caoutchouc tube was 

 finally removed and only the coils of wire left. The continuity of 

 the induced circuit was unbroken during the whole of the experiments. 



The compass was one of Wiedemann's, extremely sensitive, with 

 the magnet made aperiodic by a sufficient degree of astatizing. The 

 very slight inequality of the zinc electrodes in the tubing produced 

 a plight deflection, which was almost constant during the entire ex- 

 periment, which produces no disturbance, because the induced cir- 

 cuit is always closed. The electromagnet was removed as far from 

 the compass as my laboratory permitted; it was in another room, 

 at a distance in a straight line of 14' 6 metres. The openings and 

 closings were effected by my assistant, at bell signals given by an 

 observer sitting at the telescope. The electromagnet was turned 

 about the vertical until the action of its opening and closing was 

 without any influence on the mirror of the compass when the 

 circuit of the latter was open. The primary current was alternately 

 passed through the electromagnet in the two directions, which I will 

 call A and B. 



The following are the deflections, exactly in the order in which 

 they were obtained. Before Experiment 1 the electromagnet had 

 been traversed by the current in the direction A. 



