242 Prof. Hare on some improved Forms 



another, it is only necessary to allow a pivot of each trough 

 to revolve on pieces of sheet copper severally soldered to the 

 different ends of a rod of metal. To connect with the ter- 

 mination of the series, the leaden rods (to which are soldered 

 the vices, or spring forceps, for holding the substances to be 

 exposed to the deflagrating power) one end of each of the 

 lead rods is soldered to a piece of sheet copper. The pieces 

 of copper, thus soldered to the lead rods, are then to be duly 

 placed under the pivots, which are of course to be connected 

 with the terminations of the series. The last-mentioned con- 

 nexion is conveniently made by means of straps of copper, 

 severally soldered to the pivots, and the poles of the series, 

 and screwed together by a hand-vice. 



Fig. 1 (Plate IV.) represents an apparatus, consisting of 

 two troughs, each ten feet long, constructed in the manner 

 which I have described. Each trough is designed to contain 

 150 galvanic pairs. The galvanic series in the upper trough 

 is situated as when not subjected to the acid. In the repre- 

 sentation of the lower trough, the galvanic series is omitted, 

 in order that the interior may be better understood. The 

 series belonging to this trough may be observed below it, 

 in three boxes, each containing 50 pairs, fig. 2. In placing 

 these boxes in the trough, some space is left between them 

 and that side of the trough on which the acid enters, so that 

 instead of flowing over them, it may run down outside, and 

 rise up within them. 



The pairs of the series consist of copper cases, about seven 

 inches long by three inches wide and half an inch thick ; 

 each containing a plate of zinc equidistant from its sides, and 

 prevented from touching it by grooved strips of wood. — 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 open only at the 

 bottom and top. They are separated from each other by 

 very thin veneers of wood. 



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

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

 periments 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 soldered face 

 to face) and slid into grooves, at a quarter of an inch distance 

 from each other ; all the copper surfaces being in one direc- 

 tion, and all the zinc surfaces in the other. In this case the 



zinc 



