Proceedings of the American Philosophical Society. 49 



It consists of four troughs, each containing 100 pairs within a space of 

 about 30 inches in length. The pairs, severally, are of the Cruickshank 

 pattern, and about Qh inches square, independently of the grooves, so as 

 to expose about 42 inches of zinc surface. Every fifth plate is cemented 

 into its groove by a compound of rosin and suet. The plates, interme- 

 diate between those thus cemented, are made to fit tightly into their 

 grooves ; but in consequence of a slight obliquity in their sides, can be 

 extracted by the aid of forceps, so as to be cleansed, and, when expedi- 

 ent, scraped. The cementing of each fifth plate tends to prevent any 

 injurious retrocession of the voltaic fluid ; and yet when the intermediate 

 four plates are removed, an interstice is vacated sufficiently large to allow 

 the stationary metallic surfaces to be reached by a scraper. The plates 

 are all amalgamated, which not only renders them less susceptible of 

 wasteful reaction with iicid, but more susceptible of being cleaned. A 

 strip of wood 13 inches wide and 2 inches deep, is bored by a centre bit, 

 so as to have eight vertical and cylindrical holes, which are all supplied 

 with mercury. By means of ropes of copper wire, these holes are made 

 to communicate severally with the poles of each of the troughs, so that 

 every one of these has its corresponding mercurial receptacle. Arches 

 of twisted copper wire are provided of such various lengths, that the re- 

 ceptacles may be connected in such manner as to cause the associated 

 troughs to act either as one series of 400 pairs each of 42 inches of zinc 

 surface ; as a series of 200 pairs each of 84 inches of zinc surface ; or 

 as a series of 100 pairs each of 168 inches of zinc surface. In the usual 

 mode of constructing the voltaic apparatus, the diversities of power that 

 appertain to an apparatus in which the ratio of the size of the pairs to 

 their number varies, as above described, can be produced only by chan- 

 ges in the arrangement, which are too inconvenient to be employed ; but, 

 according to the contrivance described, are attainable simply by shifting 

 the connecting arches, so as to alter duly the mode in which the recep- 

 tacles are connected with each other. 



By means of this apparatus, the deflagration of metals, the arched flame 

 between charcoal points, the fusion of platina by contact with the aqueous 

 solution of chloride of calcium, the welding of iron wire to a rod of the 

 same metal under water, were all accomplished with the most striking 

 success. 



In repeating Davy's experiment, in which the arched flame between 

 charcoal points was subjected to the influence of a permanent magnet, 

 the reaction between the voltaic and magnetic fluids was so violent, as to 

 be productive of a noise like that of small bubbles of hydrogen inflamed 

 in escaping from the generating liquid. This last mentioned experiment 

 was performed by request of Prof. Henry, who manipulated in the per- 

 formance of it. 



Vol. XL, No. 1.— Oct.-Dec. 1840. ^ 7 



