before and after completion of the Voltaic Circuit. 287 



establish the fact, beyond any doubt, of not only the passing of 

 a distinct spark before the completion of the circuit, but the 

 practicability of continuing this action for several weeks in 

 constant succession, and enabling us to examine, with much 

 accuracy, the rationale of the action of this extraordinary ap- 

 paratus. 



5. The water battery, which I have constructed, and which 

 I am about to describe, consists of 3520 pairs, or series of 

 copper and zinc cylinders, each pair being placed in a sepa- 

 rate glass vessel, well covered with a coating of lac varnish. 

 The glass cells are placed on slips of glass, covered on both 

 sides with a thick coating of lac ; this coating being fixed by 

 heating the glass over a gas furnace, and then covering it with 

 the varnish. The 3520 cells, thus insulated, are placed on 

 forty-four separate oaken boards, also covered with lac varnish, 

 each board carrying eighty cells. The boards, or trays, slide 

 into a wooden frame, where they are further insulated by rest- 

 ing on pieces of thick plate glass, similarly varnished. 



6. It may at first sight appear that many of these precau- 

 tions are unnecessary ; in truth, had I, at the outset, expected 

 they would have been requisite, I might probably have been 

 deterred from attempting so troublesome and lengthened an 

 inquiry. At first I imitated the apparatus of Mr. Crosse, al- 

 ready referred to (3.), the copper cylinders being made water- 

 tight that they might themselves constitute the cells ; and consi- 

 dering such insulation would be sufficient, I attached the cells 

 to the boards with sealing-wax, poured into holes made in the 

 boards for the insertion of each cell. I found this arrangement 

 answer very well for a few hundred series, but when the number 

 was augmented, and the battery completed, the insulation was 

 sadly deficient. This induced me to take the battery asunder, 

 and to have distinct or separate glass vessels made for each 

 pair. After again completing the entire series, I found the 

 insulation was even less efficient than before; for from the 

 glass attracting moisture from the atmosphere, as well as from 

 the evaporation of the battery, each cell became a conductor, 

 and scarcely any effect could be produced on the electroscope \ 

 in fact, it was not until I had finally adopted the arrange- 

 ments I have previously described, that any approximation to 

 a tolerable insulation could be maintained. 



7. The general appearance of the battery may be seen by 

 referring to fig. 1, where A, A' represent the wooden frames, 

 in which are placed the forty-four boards containing the entire 

 battery; B a shelf on which a galvanometer can be placed, or 

 any other apparatus for the detection of a current or chemical 

 action. N and P are the terminals or poles of the battery. 



