The London, Edinburgh and Dublin philosophical magazine and journal of science . , G, were arranged in Fig. 1- — Ei£) ft [Wirrinnnra-^ series (fig. 1); and one poleP was connected through anammeter A with one carbonof the electric light L, theother carbon of which wasattached to a mercury troughT, which, by means of a me-tallic bridge-piece, could beconnected with any one ofthe mercury-cups B, C, D,each of which was perma-nently electrically connectedwith the terminal of a differ-ent number of cells. The two carbons were also connectedwith the terminals of a voltmeter VT, by means of which the
The London, Edinburgh and Dublin philosophical magazine and journal of science . , G, were arranged in Fig. 1- — Ei£) ft [Wirrinnnra-^ series (fig. 1); and one poleP was connected through anammeter A with one carbonof the electric light L, theother carbon of which wasattached to a mercury troughT, which, by means of a me-tallic bridge-piece, could beconnected with any one ofthe mercury-cups B, C, D,each of which was perma-nently electrically connectedwith the terminal of a differ-ent number of cells. The two carbons were also connectedwith the terminals of a voltmeter VT, by means of which thedifference of potentials between the carbons at any momentcould be determined. The experiment was made thus :—The bridge-piece was put into D, and the carbons by meansof a rack adjustment separated until a good steady light wasobtained, when readings of the ammeter and voltmeter weretaken. A second bridge-piece was now put into C and thatin D quickly withdrawn, the effect being to suddenly increase * Communicated by the Physical Society of London ; read December 9, Resistance of the Electric Arc. 347 the number of cells in circuit producing the light, increasingtherefore the current without interrupting it, and withoutchanging the distance between the carbons, as the lamphad no automatic adjusting arrangement. Readings of Aand V were then quickly taken and the operation reversed—that is, the bridge-piece put into D and that in C quicklywithdrawn, which had the effect of again reducing thecurrent; and if the change back again were effected not longafter the first, the carbons were not sufficiently burnt awayby the stronger current to make the light go out when thecurrent was reduced, so that a third set of readings of A andV could be taken. In this way, for the same distance betweenthe carbons two readings of the lower current and its corre-sponding carbon difference of potentials, and one intermediatereading of the higher current with its carbon difference ofpoten
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectscience, bookyear1840
