of the Galvanic Deflagrator, ^c. 349 



Each plate of zinc is soldered to the next case of copper, 

 on one side. This may be understood from the diagram, 

 fig. 3. It must be observed, that the copper cases are o- 

 pen only at the bottom and top. They are separated from 

 each other by very thin veneers of v(?ood. 



Fig. 4. represents a smaller trough, differing from the 

 others only in length. This I made, with a view to some 

 experiments on the comparative power of the galvanic 

 pairs of the form of copper cases, with zinc plates, above 

 described ; and those made on Cruickshank's plan, or of 

 the form used by Sir H. Davy, in the porcelain troughs. 



Fig. 5. represents a box, containing 100 Cruickshank 

 plates, (each consisting of a plate of zinc, and copper, sol- 

 dered face to face,) and slid into grooves, at a quarter of 

 an inch distance from each other; all the copper surfaces 

 being in one direction, and all the zinc in the other. In this 

 case the zinc plates are exposed only on one side. The 

 surface on which the acid can act, is therefore the same 

 as in a deflagrator of 50 pairs, in which each zinc plate is 

 assailable on both sides. It ought to be understood, that 

 the box containing the 100 Cruickshank plates is open at 

 bottom, and is of such dimensions as to occupy the place 

 of a box, containing 50 pairs of the deflagrator, receiving 

 the acid in its interstices from below, in the same manner, 

 by a partial revolution of the trough, fig. 4. 



Fig. 6. represents a box, containing 200 Cruickshank 

 plates. This diifers from the common Cruickshank trough 

 only in having the interstices as narrow as those between 

 the copper and zinc surfaces of the deflagrator pairs, rep- 

 resented by fig. 2 ; and that the mode in which the acid is 

 thrown off, or on, the whole series, does not differ, materi- 

 ally from that described in the instance of fig. 1. 



On contrasting the deflagrating power of the series of 

 50, represented at fig. 4, with Cruickshank's plates in the 

 box, that of th(; latter was found comparatively feeble, and 

 even when compared with the Cruickshank trough, fig. 6. 

 in igniting metals, or carbon, the power of the deflagrator 



