394 MEMORIAL OF JOSEPH HENRV. 



alternate poles. This was virtually an extension of the Roberts 

 series of magnetic poles, equivalent to a series of 24 of Joule's 

 riarrow magnets placed side by side and arranged radially in a 

 ring. This circular battery of magnets, excited by 16 cups arranged 

 in a series of four, lifted 2,710 pounds.* 



It will be noticed that in each of these interesting improvements 

 on the simple horse-shoe "quantity " magnet, the highest efficiency 

 was obtained by adopting Henry's system of "multiple coils." 



This system has also been most successfully applied by Z. T. 

 Gramme, of Paris, to the revolving annular inductor of his very 

 ingenious and powerful form of magneto-electric machine. 



Nate E. (From p. % 



ABSTRACT OF PAPER ON SELF-INDUCTION. 



Professor Bache, as a Secretary of the American Philosophical 

 Society, (knowing that the "Transactions" of the Body, containing 

 Henry's important Memoir, would not be formally published for a 

 year or more,) with that energetic zeal of friendship so characteristic 

 of the man, obtained permission to publish an abstract of the pre- 

 vious verbal communication; which he accordingly proceeded to 

 have at once inserted in the forthcoming number of the Franklin 

 Institute "Journal," with the following prefatory letter addressed 

 "To the Committee of Publication" of that Journal: 



GENTLEMEN: The American Philosophical Society, at their 

 last stated meeting, authorized the publication of the following 

 abstract of a verbal communication made to the Society, by Pro- 

 fessor Henry, on the 16th of January last. A memoir on this sub- 

 ject has been since submitted to the Society, containing an extension 

 of the subject, the primary fact in relation to which was observed 

 by Professor Henry as early as 1832, and announced by him in the 

 American Journal of Science. Mr. Faraday having recently entered 

 upon a similar train of observations, the immediate publication of 

 the accompanying is important, that the prior claims of our fellow 

 countryman may not be overlooked. 



Very respectfully yours, 



A. D. BACHE, 



One of the Secretaries Am. Philos. Soc. 

 Philadelphia, Feb. 7th, 1835. 



* Sturgeon's Annals of Electricity, June, 1841, vol. vi. p. 432. 



