Page:Proceedings of the Royal Society of London Vol 60.djvu/88

Rh micrometer in tw enty to th irty places, these diameters having very nearly equal values, and a mean value of 0*05245 cm. The bismuth wire so prepared was mounted on a suitable holder, and its resistance was taken at several different tem peratures and in liquid air, the temperatures being in all cases measured by our standard platinum thermometer Pi.*

The results of these measurements were as follows:—

Resistivity of Bismuth at the Temperature o f Liquid Air. 73 Resistivity of Electrolytic Bismuth. No. I. Tem perature in platinum degrees. Observed resistance in ohms. Resistivity in C.GLS. units per cubic centimetre. Rem arks. + 60° *5 4*9857 133250 A t ordinary tem perature. + 19° 4 -3464 116180 — 61° • 2 3 1275 83590 In ether cooled w ith solid carbonic acid. -2 0 2 °-2 1-5256 40780 In liquid air.

The curve of resistivity plotted from these data is shown in fig. 1, and in the table the value of the resistivity of bismuth in C.G.S. unit's per cubic centimetre is given above. These values of the resistivity show that in the case of this pure electrolytic bismuth

F io. 1.

Temperature in Platinum Degrees.

Mag.,’ J u ly, 1895, p. 100.
 * For details of this thermometer, see Dewar and Flem ing on the “ Therm oelectric Powers of Metals and Alloys at the Boiling Point of Liquid Air,” ‘ Phil.