98 Vr, Harems Dejlagrator and Calorimotor. 



With respect to the comparative powers of concentric 

 coils, of copper and zinc and of plates of those metals alter- 

 nating ; if only a few pairs are to be employed, I believe 

 it a matter of indifference which construction we adopt. I 

 have however, found to my cost that it is far from being so 

 when the series is numerous. Last summer I constructed 

 an apparatus of one hundred pairs, each containing six al- 

 (ernatcd plates, three of each metal. On trial, it proved 

 much less powerful than the Defiagrator sent to you, though 

 the zinc surface in each pair, was one seventh larger, and 

 the number of the series one fourth more extensive. The 

 exposure to each other, of the copper and zinc plates ter- 

 minating the ditferent pairs, struck me as disadvantageous. 

 ] therefore, removed the external zinc plate in each, so that 

 the pair afterwards, consisted severally of three copper and 

 two zinc plates, and were bounded by copper towards both 

 poles.- i'here was some comparative gain by this change, 

 as the power was not lessened in proportion to the diminu- 

 tion of zinc surface. Still the result was unsatisfactory. 1 

 then had some boxes made with partitions of glass, to be in- 

 terposed between the pairs of the series. These were em- 

 ployed as is usual with galvanic troughs, made with parti- 

 tions, excepting the deficiency of bottoms, and their being 

 suspended to the beams, so as to be simultaneously immers- 

 ed with the galvanic surfaces which they were intended to 

 insulate. The power of the series was not amended by this 

 contrivance. It had often occured to me, that surrounding 

 the zinc by Copper, might be an indispensable feature in 

 the arrangement of my Deflagrator of coils. In order to test 

 the correctness of this surmise, I pioceeded to form an ap- 



would liave no perceptible influence on masses that might be sensibly ig'tii- 

 ted by larger pairs. Theje characteristics weie fully demonstrated, not on- 

 ly by my own apparatus, but \>y those constructed by Messrs. Wetherilland 

 Feale, and which were larger, but less capable of exciting intense ignition. 

 Mr. Peale's apparatus contained nearly seventy .square feet, Mr. Wether- 

 ill's nearly one hundred, in the form of concentric coils, yet neither could 

 produce a heat above redness on the smallest wires. At my suggTstion, Mr. 

 I'eale separated the two surfaces in his coils into four alternating, constitu- 

 ting two galvanic pairs in one recipient. Iron wire was then easily burned 

 and platina fused by i(. These facts, together with the incapacity of the 

 calorific fluid extricated by the calorimotor to permeate charcoal, next to 

 metals the be>t electrical conductor, must sanction the position I assigned to 

 it as being in the opposite extreme from the columns of De Luc and Zamboni. 

 Foi'Hs in these, the phenomena are such as are characteristic of pure elec- 

 tricity, so in one very large galvanic pair, they almost exclusively demon- 

 strate the agency of pure caloric. 



