98 Dr. Hare's JDejlagrator and Calorimolor. 



With respect to the comparative powers of concentric 

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

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

 it a matter of inditTerence which construction we adopt. I 

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

 when the series is nunaerous. Last sumnaer I constructed 

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

 ternated plates, three of each nnetaK On trial, it proved 

 nujch less powerful than the Deflagrator 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 different pairs, struck me as disadvantageous. 

 I therefore, removed the external ziuc plate in each, so that 

 the pair afterwards, consisted severally of three copper and 

 two zinc plates, and were hounded by copper towards both 

 poles. There 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. I 

 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 proceeded to form an ap- 



L 



would have no perceptible influence on masses that might be sensibly igni- 

 ted by larger pairs, 'f'hese cliaracteristics were fully domoustrated, not on- 

 ly by my own apparatus^ but by those constructed by Messrs. Wetlierill and 

 Peale, and which were liu'sfer^ but less capable of exciting- intense ignition. 

 Mr. Peale's apparatus contained nearly seventy square f^et, Mr. Wether- 

 ill -g nearly one hundred, in the form of concentric coils, yet neither could 

 produce a heat above redne^^s on the smallest wire?. At my suggestion, Mr- 

 Feale separated the two surraces in his coils into four alternating, constitu- 

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

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

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

 metals tbe best electrical conductor, must sanction the position I assigned to 

 it as being in the opposite extreme from the columns of l)e Luc and Zamboni. 

 For as in these, the phenomena are such as are characteristic of pure elec- 

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

 ??trate the agency of pure caloric. 



