On Ellectro-Dynamic Induction. . 135 
metal, except iron, between the conductors. The other part is 
of considerable intensity, is not intercepted by a drop of water, 
develops the magnetism of hardened steel, gives shocks and is 
screened or neutralized by a closed coil, or a plate of any kind of 
metal. Also, the induced current produced by moving a conduc- 
tor towards or from a battery current, and that produced by the 
movement up and down of a battery in the acid, are of the na- 
ture of the first mentioned part, while the currents of the third, 
fourth, and fifth orders partake almost exclusively of the proper- 
ties of the second part. 
53. The principal facts and conclusions of this section were 
announced to the Society in October, 1839, and again presented 
in the form in which they are here detailed in June last. 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 the last No. of my contributions 
were merely arranged under different heads, and only such infe- 
rences drawn from them as could be immediately deduced with- 
out reference to a general explanation. The addition, however, 
_ Which I have since made to the number of facts, affords the 
means of a wider generalization ; and after an attentive consid- 
eration of all the results given in this and the preceding papers, 
I have come to the conclusion that they cau all be referred to the 
Simple laws of the induction at the beginning and the ending of 
a galvanic current. 
55. In the course of these investigations the limited hypothe- 
ses which I have adopted have been continually modified by the 
development of new facts, and therefore my present views, with 
the farther extension of the subject, may also require important 
Corrections. But I am induced to believe, from its exact accor- 
dance 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 approximation, and will therefore be of some 
