IN INCREASING THE INTENSITY OF ELECTRICITY. 545 



15. The spiral conductor produces, however, little or no increase of 

 effect wiien introduced into a galvanic circuit of considerable intensity. 

 Thus when the large spiral used in experiment seventh, eighth, &c. was 

 made to connect the poles of two Cruikshank's troughs, each containing 

 fifty-six four-inch plates, no greater effect was pei'ceived than with a 

 short thick wive : in both cases in making the contact a feeble spark 

 was given, attended with a slight deflagration of the mercury. The 

 batteries at the same time were in sufficiently intense action to give a 

 disagreeable shock. It is probable, however, that if the length of the 

 coil were increased in some proportion to the increase of intensity, an 

 increased effect would still be produced. 



In operating with the apparatus described in the last experiment, a 

 phjenomenon was observed in reference to the action of the battery 

 itself, which I do not recollect to have seen mentioned, although it is 

 intimately connected with the facts of magneto-electricity, as well as 

 with the subject of these investigations, viz. When the body is made to 

 form a part of a galvanic circuit composed of a number of elements, a 

 shock is, of course, felt at the moment of completing the circuit. If 

 the battery be not very large, little or no effect will be perceived during 

 the uninterrupted circulation of the galvanic current ; but if the circuit 

 be interrupted by breaking tlie contact at any point, a shock will be felt 

 at the moment, nearly as intense as that given when the contact was 

 first formed. The secondary shock is rendered more evident, when 

 the battery is in feeble action, by placing in the mouth the end of one 

 of the wires connected with the poles ; a shock and flash of light will 

 be perceived when the circuit is completed, and also the same when 

 the contact is broken at any point ; but nothing of the kind will be per- 

 ceived in the intermediate time, although the circuit may continue un- 

 interrupted for some minutes. This I consider an important fact in 

 reference to the action of the voltaic current. 



The phgenomena described in this paper appear to be intimately con- 

 nected with those of magneto-electricity, and this opinion I advanced 

 with the announcement of the first fact of these researches in the Ame- 

 rican Journal of Science. They may, I conceive, be all referred to that 

 species of dynamical Induction discovered by Mr. Faraday, which pro- 

 duces the following phaenomenon, namely : when two wires, A and B, 

 are placed side by side, but not in contact, and a voltaic current is 

 passed through A, there is a current produced in B, but in an opposite 

 direction. The current in B exists only for an instant, although the 

 current in A may be indefinitely continued ; but if the current in A be 

 stopi)ed, tiiere is produced in B a second current, in an opposite direc- 

 tion iiowever to the first current. 



The aljove fundamental fact in magneto-electricity appears to me to be 

 a direct consequence of the statical principles of "Electrical Induction" 



