y6o 



NUMERICAL CONSTANTS. 



In conclusion, the measurements of M. Ed. Becquerel* give 

 for the couples formed by various metals or alloys, taking i'oy volt 

 for the sulphate of copper couple to which they are referred : 



The bismuth-copper couple has often been taken as a standard, 

 its course being pretty regular between the temperatures of o and 

 1 00, but the results obtained for this couple are very discordant. 



According to M. Regnault,* a volt is equal to 3 sulphate of zinc 

 and cadmium couples, and each of these again to 55 bismuth-copper 

 couples, between the temperatures of o and 100; so that a volt 

 would be equal to about 165 bismuth-copper couples. The mea- 

 surements of M. Ed. Becquerel would give 239 couples, and those 

 of Fleeming Jenkin a. number varying between 100 and 210, ac- 

 cording to the state of the bismuth. 



* En. BECQUEREL. Ann. de Chim. et de Phys. [4], Vol. vin., p. 389. 1866. 

 f The current goes from the metal to the copper by the hot junction, or 

 conversely, according as the electromotive force is positive or negative. 



% J. REGNAULT. Ann. de Chem. et de Phys. [3], Vol. LXIV., p. 453. 1854. 



