326 



BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



liquid insinuating itself into the fissures impairs the power 

 of the instrument by destroying the insulation of the cells. 

 They are superseded by more modern instruments. 



Price of a set of 20 plates, $12.00. 



Fi s 333. The Galvanic Bat- 



tery old form. (Fig. 

 385.) This instru- 

 ment consists of a 

 trough, which has 

 usually been made 

 of earthenwaie, with 

 partitions of the same 

 material, but may be 

 made of baked maho- 

 gany with partitions 

 of glass ; each trough 

 usually has eight or 

 twelve cells. The 

 zinc and copper plates 

 are connected together in pairs, by a slip of metal passing 

 from the one and soldered to the other ; each pair being so 

 placed as to inclose a partition between them, and each cell 

 containing a plate of zinc, connected with the copper plate 

 of the succeeding cell, and a copper plate joined with the 

 zinc plate in the preceding cell. The plates are connected 

 together by a bar of baked wood, so as to allow of their 

 being let down into the cells, or lifted out together. This 

 battery was formerly much used, but the more recent im- 

 provements have entirely superseded it on account of their 

 superiority. Price, $10.00. 



Hare's Deflagralor. (Fig. 386, next page.) The arrange- 

 ment shown in the figure, is that of Dr. Hare, of Philadel- 

 phia. A galvanic series, A, A, fixed in a trough,~is combined 

 with another trough, B, B, destitute of plates, and of a 

 capacity sufficient to hold all the acid necessary for an 

 ample charge. The trough containing the series is joined 

 to the other lengthwise, edge to edge ; so that when the 

 sides of the one are vertical, those of the other must be 

 horizontal. The advantage of this is, that by a partial 

 revolution of the two troughs, thus united, upon pivots that 



