329 



any lesser number of them, the connexions being made at pleasure 

 in the experimenting room. 



The rheomotor employed was an insulated voltaic battery con- 

 sisting of twelve troughs, each of twelve elements, which had been 

 several weeks in action. 



First Series. 



The following experiments show that the iron envelope of the com- 

 pound conductor gives rise to the same phenomena of induction 

 which occur when the insulated wire is immersed in water, as in 

 Dr. Faraday's experiments. 



Exp. 1. One end. of the entire length, 660 miles, was brought in 

 connexion with one of the poles of the battery, the other end re- 

 maining insulated. The wire became charged with negative elec- 

 tricity when its end touched the zinc pole, and with positive elec- 

 tricity when it communicated with the copper pole. A current, 

 indicated by a galvanometer placed near the battery, existed as long 

 as the charge was going on, and ceased when it arrived at its maxi- 

 mum. [The feeble current attributed to imperfect insulation, which 

 continues as long as the contact with the battery remains, is here left 

 out of consideration.] When the wire was charged, and the dis- 

 charge effected by a wire communicating with the earth, the current 

 produced was in the same direction, whether the discharge was made 

 near the battery or at the opposite end ; f . e. the current in both 

 cases proceeded from the wire to the earth in the same direction. 



Exp. 2. On bringing one end of the wire in contact with one of 

 the poles of the battery, the other pole having no communication 

 with the earth, the wire remained uncharged. A very slight and 

 scarcely perceptible tremor was observed in the galvanometer needle 

 interposed between the battery and the wire. 



Exp. 3. To each of the poles of the battery was attached a wire 

 220 miles in length, and similar galvanometers were interposed be- 

 tween the two wires (the remote extremities of which remained in- 

 sulated) and the battery. So long as one wire alone was connected 

 with the battery no charge was communicated to it, but on connect- 

 ing the other wire with the opposite pole both wires were instan- 

 taneously charged, as the strong deflection of both needles rendered 

 evident. On bringing the free end of one of the wires in communi- 



