75 NUMERICAL CONSTANTS. 



condition, and we can at present give anything scarcely but the 

 mean values. 



Mean Coefficient between o and 20. 



Silver 0*377. io~ 2 to 0-405. io~ a * 



Copper 0-388 



Gold 0*365 



Aluminum 0*390! 



Platinum 0*247! 



Iron 0*453! 



Tin 0-365 



Lead 0*387 



Antimony 0*389 



Bismuth 0*354 



Mercury 0*0887:}: 



Alloy2PH-iAg .... 0*022 to 0*031 1 



,, 2Au + iAg. . . . 0*065 



,, 9Pt+iIr .... 0*133* 

 German Silver .... 0*028 to 0*044 



The numbers without any reference are deduced from the 

 experiments of Matthiesen. 



Low Temperatures. \\ 



I 



Silver .... 0*305. io~ 2 between + 30 and - 120 

 Aluminum . . 0*388 ,, 28 ,, - 90 



Magnesium . . 0*390 ,, o ,, - 88 



Tin 0-424 ,, o ,, - 85 



Copper . . . 0*418 ,, o ,, - 58 



... 0-425 ,, -69 ,, -123 



Iron .... 0-490 ,, 9 ,, - 92 



Platinum . . . 0-342 ,, 95 



Solid Mercury . 0*407 ,, 40 ,, - 92 



For very high temperatures, and as far as 1000, Sir W. Siemens 

 finds that the resistance, as a function of the absolute temperature T 



* CH. RIVIERE. 1884. 



t BENOIT. Comptes rendus, Vol. LXXVI., p. 345. 1873. 



J Lord RAYLEIGH takes 0*0861 and M. LENZ 0-0879. 



MASCART, DE NERVILLE, and BENOIT, loc. ctt. 



II CAILLETET and BOUTY. Comptes rendus, Vol. c., p. 1188. 1885. 



