1840] WRITINGS OF JOSEPH HENRY. 159 



At the Beginning. At the Ending. 

 Primary current + + 



Secondary current — + 



Current of the third order + — 



Current of the fourth order — + 



Current of the fifth order + — 



26. These two series, at first sight, may appear very dif- 

 ferent, but with a little attention, they will be seen to be of 

 the same nature. If we allow that the induction at the end- 

 ing of a galvanic battery should be opposite to that at the 

 beginning of the same, then the sign at the top of the second 

 column may be called minus instead of plus, and we shall 



have the second series 1 \- alternating precisely like 



the first. 



27. In connection with the results given in the last two 

 paragraphs, it is due to Mr. Sturgeon that I should state, 

 that in a letter addressed to me and published in the Annals 

 of Electricity, he has predicted from his theory, that I would 

 find on examination the series of alternation of currents 

 for the beginning induction which I have here given. I 

 may however here add, it appears to me that this result 

 might have been predicted without reference to any theory. 

 There was no reason to suppose the induction at the begin- 

 ning would be different in its nature from that at the end- 

 ing, and therefore the series which would be produced from 

 the former might be immediately inferred from that belong- 

 ing to the latter, by recollecting that the direction of the 

 induction at the beginning should be opposite to that at the 

 ending. I do not wish it to be supposed however from this 

 remark, that I had myself drawn any inference from my 

 experiments as to the alternations of currents which might 

 be produced by the beginning induction; the truth is, that 

 this action was so feeble with the arrangement of apparatus 

 I employed, that I supposed it could not produce a series of 

 currents of the different orders. 



28. In the course of the experiments given in this section, 

 I have found that a shock can be produced without using a 

 coil, by arranging about ten elements of the battery in the 

 form of a circle, and placing the helix within this. The 



