994 Transactions of the American Institute. 



surrounding an electro-magnet, and laid the^wmdation for tlie tliird 

 species of current induction, which we shall call volta magnetic- 

 electric induction. The three species, volta electric induction, 

 magneto-electric induction, and volta magneto-electric induction, 

 are, undoubtedly, results from the action of electricity; but, as 

 they are all produced under diiferent arrangements and conditions, 

 it is important to preserve these distinctions. 



On the 18th December, 1834, Faraday communicated to the 

 Royal Society an interesting paper " on the influence by induction 

 of an electric current on itself," containing an account of the dis- 

 covery of the production of sparks and shocks from a single voltaic 

 j)air. Faradaj-^ received his information on this point from Mr. 

 William Jenkins, who must, therefore, in the absence of any other 

 record, be considered the discoverer of this important and interest- 

 ing fact. Faraday ingenuously relates the circumstance as folloAA's: 

 Mr. Jenkins infomied hini that " if an ordinary wire of short 

 length be used as the medium of communication between the two 

 plates of a battery of a single pair of metals, no management will 

 enable the experunenter to obtain an electric shock from this wire; 

 but if the wire which surrounds an electro-magnet be used, a shock 

 is felt each time the contact with the electromotor is broken, pro- 

 vided the ends of the wire .be grasped, one in each hand." This 

 discovery rests upon the same principle as that of Prof. Henry's, 

 Already cited, as announced by him in 1831; but its distinguishing 

 interest and importance consists in the production of sparks and 

 shocks from a single voltaic pair. Faraday also announced the 

 same in the November number of the London and Edinburgh 

 PJiilosoijJiiccd Magazine for 1834. Faraday used two helices coiled 

 around a paste-board tube — one ninety-six, and the other ninct}^- 

 four and a half feet in length, the former to • transmit the battery 

 current, and the latter to exhibit the induced current. Sparks and 

 shocks were obtained from the inducing or first helix, and sparks 

 from the second helix, but no shocks. It will l)e noted here, that 

 both the helices were about the same length. An iron bar was 

 introduced in the paste-board tube to increase the intensity of the 

 induced currents. 



On the 16th January, 1835, Prof. Henry made a communication 

 to the American Philosophical Society on the same su1)ject, and his 

 paper, with.the following title, was read on the 6th February, 1835: 

 " On the influence of a spii-al conductor in increasing the intensity 

 of electricity from a galvanic arrangement of a single jjair." 



