jPr. Harems Dejlagrator cmd Calorimoior. 99 



paratus of pairs, each consisting of a case of copper, con- 

 taining one zinc plate of seven inches by three, the size us- 

 ed, in the apparatus above described. (See the plate at the 

 end.) In these pairs, as in (hose contrived by Wollaston, 

 the edges of the zinc were supported by grooved pieces of 

 wood passing between them and the copper. There was, 

 however, this apparently slight, but really important differ- 

 ence, that the cases employed by me, were open at top 

 and bottom, instead of exposing the edges of the zinc late- 

 rally, as in WoUaston's. One hundred galvanic pairs, thus 

 made, were suspended to two beams, each holding fifty. 

 Between each case, a piece of pasteboard soaked in shell lac 

 varnish, was intersposed ; so that the whole constituted a 

 compact mass, into which a fluid could not enter, unless 

 through the interstices purposely preserved between the 

 copper and zinc. The phenomena produced by this appa- 

 ratus, on immersion, were upon the whole more interesting 

 than those produced by my original deflagrator ; especially 

 in the length of the jet between the poles, and the power of 

 permeating charcoal. Yet the apparatus was comprised 

 within one eighth of the space, and is not (in oxidizable 

 superficies) of half the extent. 



Having added three more beams, of fifty pairs each, to 

 my apparatus, I found the power increased fully in the ratio 

 of the number. You know that my eyes are naturally very 

 strong. The light produced by the compound blowpipe,* 

 though I operated without glasses, only dazzled them for a 

 time, and hitherto I had felt no other inconvenience from 

 my galvanic experiments. Rendered thus bold by previ- 

 ous immunity, 1 still dispensed with the annoyance of spec- 

 tacles. In consequence, my eyes, after operating with the 

 last mentioned series oftwohundredandfifty, were on the fol- 

 lowing day so much inflamed, as to be blood shot, and pain- 

 fully susceptible of the day light. The judicious applica- 

 tion of twenty leeches to each of the eye-lids, pursuant to 

 the advice of my friend. Dr. Dewees, afforded me surpri- 

 sing relief, and my eyes are now well enough to finish this 

 letter, though a few days since when I began it, I was under 

 the necessity of employing an amanuensis. 



By this series of 250, Barytes was deflagrated ; and the 

 Platina which supported it destroyed like pasteboard before 



* Since called Hydro-oxy]^ea Blowpipe. 



