494 MEMORIAL OF JOSEPH HENRY. 



claim set up for Faraday, because Fatraday expressly states in his 

 paper read before the E-oyal Society on January 29, 1835, that 

 "The inquiry arose out of a fact communicated to me by Mr. Jenkin, 

 which is as follows : If an ordinary wire of short length be used as 

 the medium of communication between the two plates of an elec- 

 tromotor consisting of a single pair of metals, no management will 

 enable the experimenter 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 electro-motor is broken, provided 

 the ends of the wire be grasped one in each hand." Notwithstand- 

 ing this explicit statement of Faraday's, neither to Henry nor to 

 Jenkin is generally accorded the credit for the original observations, 

 but it is given to Faraday. This is accounted for by the fact that 

 although Henry had the good fortune to anticipate others in the 

 observations, he had not the leisure to follow up these observations 

 to their full explanation till after Faraday had completely unravelled 

 their nature. This was owing to the removal of Henry to Princeton 

 in November of 1 832, shortly after he had made his few preliminary 

 experiments ; and he did not resume and finish this research till 1834 ; 

 and in 1835 he gave the results of his work to the American Philo- 

 sophical Society in a paper "On the Influence of a Spiral Conductor 

 in Increasing the Intensity of Electricity from a Galvanic Arrange- 

 ment of a Single Pair, etc." 



In 1838, after Henry's return from his first visit to Europe, he 

 discovered an entirely new class of phenomena in electrical induc- 

 tion ; and as the field was entirely his own he entered into this work 

 with great enthusiasm. In these researches he extends greatly our 

 knowledge of electrical induction. He .first showed that an induced 

 current may excite a second induced current in a neighboring closed 

 conductor, and this last may induce a third current in another 

 neighboring closed circuit, and so on. These various induced cur- 

 rents Henry styled currents of the first, second, third, fourth, fifth, 

 &c., orders. He shows that these currents alternate in their direc- 

 tions in the successive orders, — at least when these currents are 

 induced by the discharge of a voltaic battery. He investigates the 

 differences in the properties of these currents according as they flow 

 through conductors formed of few convolutions of low resistance or 



