108 WRITINGS OP JOSEPH HENRY. [1838 



CONTRIBUTIONS TO ELECTRICITY AND MAGNETISM. No. III. 

 ON ELECTRO-DYNAMIC INDUCTION. 



(Transactions American Philosophical Society, n. s., vol. vi, pp. 303-337.)* 

 Read November 2, 1838. 



INTRODUCTION. 



1. Since my investigations in reference to the influence 

 of a spiral conductor, in increasing the intensity of a gal- 

 vanic current, were submitted to the Society, the valuable 

 paper of Dr. Faraday, on the same subject, has been pub- 

 lished, and also various modifications of the principle have 

 been made by Sturgeon, Masson, Page, and others, to increase 

 the effects. The spiral conductor has likewise been applied 

 by Cav. Antinori to produce a spark by the action of a 

 thermo-electrical pile ; and Mr, Watkins has succeeded in ex- 

 hibiting all the phenomena of hydro-electricity by the same 

 means. Although the principle has been much extended 

 by the researches of Dr. Faraday, yet I am happy to state 

 that the results obtained by this distinguished philosopher 

 are not at variance with those given in my paper. 



2. I now offer to the Society a new series of investigations 

 in the same line, which I hope may also be considered of 

 sufficient importance to merit a place in the Transactions. 



3. The primary object of these investigations was to dis- 

 cover, if possible, inductive actions in common electricity 

 analogous to those found in galvanism. For this purpose a 

 series of experiments was commenced in the spring of 1836, 

 but I was at that time diverted, in part, from the immediate 

 object of my research, by a new investigation of the phe- 

 nomenon known in common electricity by the name of the 

 lateral discharge. Circumstances prevented my doing any- 

 thing further, in the way of experiment, until April last, 

 when most of the results which I now offer to the Society 

 were obtained. The investigations are not as complete in 

 several points as I could wish, but as my duties will not per- 



* [The title page of vol. vi bears date 1839.] 



