136 Contributions to Electricity and Magyietism. 



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 the ex- 

 planation of the phenomena, they may be stated as follows : — 1, 

 During the time a galvanic current is increasing in quantity in a 

 conductor, it induces, or tends to induce, a current in an ad- 

 joining parallel conductor, in an opposite direction to itself. 2. 

 During the continuance of the primary current in full quantity, 

 no inductive action is exerted. 3. But when the same current 

 begins to decline in quantity, and during the whole time of its 

 diminishing, an induced current is produced in an opposite direc- 

 tion to the induced current at the beginning of the primary cur- 

 rent. 



B7. In addition to these laws, I must frequently refer to the 

 fact, that when the same quantity of electricity in a current of 

 short duraton is passed through a galvanometer^ the defieciing 

 force on the needle is the same, whatever he the intensity of the 

 electricity. By intensity is here understood the ratio of a given 

 quantity of force to the time in which it is expended ;* and ac- 

 cording to this view, the proposition stated is an evident inference 

 from dynamic principles. But it does not rest alone on conside- 

 rations of this kind, since it has been proved experimentally by 

 Dr. Faraday, in the third series of his researches. 



58. In order to form a definite conception of the several con- 

 ditions of the complex phenomena which we are about to inves- 

 tigate, I have adopted the method often employed in physical in- 

 quiries, of representing the varying elements of action by the 

 different parts of a curve. This artifice has been of much assis- 

 tance to me in studying the subject, and without the use of it at 

 present, I could scarcely hope to present my views in an intelli- 

 gible manner to the Society. 



59. After making these preliminary statements, we will now 

 proceed to consider the several phenomena; and, first, let us take 

 the case in which the induction is most obviously produced in 

 accordance with the laws as above stated, (56,) namely, by im- 

 mersing a battery into the acid, and also by withdrawing it from 



'* Or more strictly speaking, the ratio of two quantities of the same species rep- 

 resenting the force and the time. 



