Conductibility of Liquids for Electricity, 467 



dynamic induction in liquids might furnish a means of submitting 

 this opinion to an experimental test, by trying whether the 

 electrodes, employed in that experiment to conduct the instan- 

 taneous current of the fluid helix to the galvanometer, are or 

 are not polarized by this current. To obtain a decisive effect it 

 was necessary to reproduce the phsenomenon with more intensity 

 than when, as in your experiments, the question was merely to 

 prove the phaenomenon itself. For this purpose we made use 

 of a tube of vulcanized Indian rubber, of about 1 centimetre in 

 internal diameter and 13 metres in length. We twisted it round 

 the two branches of the large electro-magnet intended for experi- 

 ments in diamagnetism, which, if we are not mistaken, has the 

 same form and the same dimensions as your own ; it is covered 

 by a coil of copper wire 3 millimetres in diameter and 180 metres 

 long. The tube was entirely filled with a mixture of 6 parts by 

 volume of water and 1 part of sulphuric acid. It was terminated 

 at both ends by glass tubes of about 4 centimetres in length ; 

 into each of these passed a platinum wire of 1 millimetre in 

 diameter, the portion of which immersed in the liquid was about 

 2"5 centimetres in length. All being thus arranged, the ends 

 of the two platinum wires were connected with the galvanometer 

 of 1800 coils which was placed at a distance of 10 metres. We 

 had ascertained previously that at this distance the magnet did 

 not exercise any sensible action upon the needles. The moment 

 the two ends of the copper- wire coil of the electro-magnet were 

 put in connexion with the poles of a Grove's battery of 60 large 

 elements, arranged in a double series of 30, the needle of the 

 galvanometer deviated suddenly about 40°, and returned, after 

 oscillations which occupied between 1 and 2 minutes, to 0°. 

 When the circuit of the pile was interrupted, the galvanometer 

 deviated again about the same number of degrees, but in the 

 opposite direction, returning again to 0° in the same manner. 

 The needle returning in both cases to 0°, one would be tempted, 

 at first sight, to think that there was no polarization of the elec- 

 trodes. But the strong impulsion communicated to the very 

 astatic system of the galvanometer by the induced current, 

 causing the needles to oscillate during a considerable period 

 as we have just stated, the circuit remaining always complete, it 

 appeared possible that the polarization, if it existed, had already 

 exhausted itself before the needles had arrived at a state of repose. 

 To get rid of this difficulty we put the two electrodes in direct 

 communication with each other by means of a copper wire of 

 only 10 centimetres in length, although they still remained in 

 connexion with the galvanometer. The induced current pro- 

 duced when the circuit of the pile was established, then passed 

 by this wire rather than by the infinitely longer wire of the 



