118 Contributions to Electricity and Magnetism. 



another communication. After considerable delay, occasioned by 

 alterations in the rooms of the physical department of the col- 

 lege, I was enabled to resume my researches, and since then I 

 ha\^e been so fortunate as to discover a series of new facts belong- 

 ing to different parts of the general subject of my contributions. 

 These I have announced to the Society at different times, as they 

 were discovered, and I now purpose to select from the whole such 

 portions as relate particularly to the principal subject of my last 

 paper, namely, the induction at the beginning and ending of a 

 galvanic current, and to present them as a continuation, and, in 

 a measure, as the completion, of this part of my researches. The 

 other results of my labors in this line will be arranged for publi- 

 cation as soon as my duties will permit me to give them a more 

 careful examination. 



2. In the course of the experiments I am about to describe, I 

 have had occasion to repeat and vary those given in my last pa- 

 per, and I am happy to be able to state, in reference to the results, 

 that, except in some minor particulars, which will be mentioned 

 in the course of this paper, I have found no cause to desire a 

 change in the accounts before published. My views, however, 

 of the connection of the phenomena have been considerably mod- 

 ified, atid I think rendered much more definite by the additional 

 light which the new facts have afforded. 



3. The principal articles of apparatus used in these experiments 

 are nearly the same as those described in my last paper, namely, 

 several flat coils and a number of long wire helices. (III. 6, 7, 

 8.)* I have, however, added to these a constant battery, on Pro- 

 fessor Daniell's plan, the performance of which has fully answered 

 my expectations, and confirmed the accounts given of this form 

 of the instrument by its author. It consists of thirty elements, 

 forped of as many copper cylinders, open at the bottom, each 

 five inches and a half in height, three inches and a half in diam- 

 eter, and placed in earthen cups. A zinc rod is suspended in each 

 of these, of the same length as the cylinders, and about one inch 

 in diameter. The several elements are connected by a thick cop- 

 per wire, soldered to the copper cylinder of one element, and dip- 

 ping into a cup of mercury on the zino of the next. The cop- 



* When the numerals II or III are included in the parenthesis, reference is made 

 to the corresponding Nos. of my contributions. 



n 



