1840] WRITINGS OF JOSEPH HENRY. 169 



Postscript. 



53. The principal facts and conclusions of this section 

 were announced to the Society in October, 1839, and again, 

 in June last, presented in the form in which they are here 

 detailed. Since then however I have had leisure to examine 

 the subject more attentively, and after a careful comparison 

 of these results with those before given, I have obtained the 

 more definite views of the phenomena which are given in the 

 following section. 



SECTION III. 



Theoretical Considerations relating to the Phenomena described 

 in this and the preceding Communications. 



Read November 20, 1840. 



54. The experiments given in number III of my Con- 

 tributions were merely arranged under different heads, and 

 only such inferences drawn from them as could be imme- 

 diately deduced without reference to a general explanation. 

 The addition however which I have since made to the num- 

 ber of facts, affords the means of a wider generalization ; and 

 after an attentive consideration of all the results given in 

 this and the preceding papers, I have come to the conclusion 

 that they can all be referred to the simple laws of the induc- 

 tion at the beginning and the ending of a galvanic current. 



55. In the course of these investigations the limited hypoth- 

 eses which I have adopted have been continually modified 

 by the development of new facts, and therefore my present 

 views, with the further extension of the subject, may also 

 require important corrections. But I am induced to believe, 

 from its exact accordance with all the facts, so far as they 

 have been compared, that if the explanation I now venture 

 to give be not absolutely true, it is so at least in approxima- 

 tion, and will therefore be of some importance in the way of 

 suggesting new forms of experiment, or as a first step towards 

 a more perfect generalization. 



56. To render the laws of induction at the beginning and 

 the ending of a galvanic current more readily applicable to 



