170 WRITINGS OF JOSEPH HENRY. [1840 



the explanation of the phenomena, they may be stated as 

 follows : 1. During the time a galvanic current is increas- 

 ing in quantity in a conductor, it induces, or tends to induce, 

 a current in an adjoining 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 direction to the induced 

 current at the beginning of the primary current. 



57. In addition to these laws, I must frequently refer to 

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

 of short duration is passed through a galvanometer, the deflecting 

 force on the needle is the same, whatever be 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 according to this view, the proposition stated is an evi- 

 dent inference from dynamic principles. But it does not 

 rest on considerations of this kind alone, 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 

 conditions of the complex phenomena which we are about 

 to investigate, I have adopted the method often employed 

 in physical inquiries, of representing the varying elements 

 of action by the different parts of a curve. This artifice has 

 been of much assistance to me in studying the subject, and 

 without the use of it at present, I could scarcely hope to 

 present my views in an intelligible 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 immersing a battery into the acid, and also by 

 withdrawing it from the same. During the time of the 

 descent of the battery into the liquid, the conductor con- 

 nected with it is constantly receiving additional quantities 



*0r, more correctly speaking, the ratio of two quantities of the same 

 species, representing the force and time. 



