THE 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] I 



DECEMBER 1897. 



LVIII. On Platinum Temperatures. 

 By J. D. Hamilton Dickson, M.A., F.R.S.E* 



^7~ARIOUS formulae have been suggested connecting the 

 electric resistance of a metallic wire with its tempera- 

 ture. The earliest of these was given by Clausiusf, in 1858, 

 on the results of Arndtsen's experiments. Neglecting iron, 

 winch then as now seems anomalous, he found that Arndtsen's 

 results were nearly represented by the formula 



R = Bo(l + -00366«), (1) 



where R is the resistance at t° C, and R is the resistance at 

 the freezing-point of water. The constant in this formula 

 being the same as that in Gray-Lussac's law for the relation 

 between the volume and the temperature of a gas at constant 

 pressure, he added that this might probably be the real value 

 of the constant for pure metals, and in that case their resist- 

 ance would vanish at the absolute zero. This formula held 

 for all Arndtsen's metals except iron. 



SiemensJ, in the Bakerian Lecture for 1871 (only a sum- 

 mary of which was published by the Royal Society), on 

 theoretical grounds gave the formula 



U=~R + ay/t + bt, (2) 



where a and b are constants. 



* Communicated by the Author, 

 t Pogg. Ann. vol. civ. (1858). 

 \ Proc. Roy. Soc. 1870-71. 



Phil. Mag. S. 5. Vol. 44. No. 271. Dec. 1897. 2 L 



