Description of a Carbon Voltaic Battery. 185 



very considerably the power of the battery, which with proper 

 arrangements liberates six cubic inches of gas per minute, heats 

 to a bright red seven inches of platinum wire one fortieth of an 

 inch in diameter, burns with beautiful scintillations steel needles 

 of a similar diameter, and affects proportionately the magnet. 

 The battery consists of four pairs of zinc and platinum foil plates, 

 each metal exposing a surface of fourteen square inches; the 

 whole occupies less space than a cube four inches in the side." 



I was agreeably surprised on reperusing this article, after the 

 publication of my note above referred to, to find how favorable 

 the comparison was between the plumbago and the platina. 

 The platina battery of Mr. Grove exposed one hundred and twelve 

 square inches of surface, the plumbago one hundred and twenty j 

 the former gave one cubic inch of gas in ten seconds, the latter 

 one cubic inch in twelve seconds. 





The form of carbon most efficient in voltaic circuits, is that 

 exceedingly hard and pure carbon which is deposited from coal 

 gas on the heated inner surface of the retorts of the gas works ; 

 but it is so difficult to work it into shape, and to attach it to other 

 substances, that it cannot be availed of. I have tried anthracite 

 and bituminous coal, but not with success. 



In the battery described in this article, as actually constructed, 

 the two elements were, by mistake, placed at a greater distance 

 than I had intended, and no doubt much power is by that means 

 lost. In another apparatus which I am constructing, it is my in- 

 tention to remedy this defect. Nearness of approach between 

 the elements cannot be too much looked to in such arrangements. 



In the c Archives de TEIectricite,' (No. 1, p. 262,) M. De La 

 Rive gives an account of some experiments made by him with 

 a Grove's battery of forty pairs. He states the luminous arch 

 produced between the poles, after contact and gradual separation, 

 to be one inch in length. That produced by the subject of this 

 paper, was about two inches, but was not accurately measured, 

 nor was it taken in vacuo. 



By way of illustration, I would remark, that the large Wollas- 

 tonian arrangement before alluded to, when new, gave an arch 

 in the open air of seven inches, and may now be usually de- 



pended on for an arch of from four to five inches in length. 



M. De La Rive further observes that the transfer of particles 

 of carbon from the positive to the negative pole is evident, and 



Vol. xjliv, No. 1— Oct.-buc. Ib42. 24 



