186 Mr Laws, Experiments on the Thomson Effect 



Table II. 



Joule effect. 

 G = 2 amperes. 



Mean value for d : 2-79. 



Substituting in the expression for a given above (p. 184) the 

 value <r 30 ° = — 863 ergs per c.G.S. unit current per 1° C. is obtained. 



At 23°"8 the values — 847, — 857 were obtained with currents 

 of 3 and 4 amperes respectively. 



The value found by Batelli was — 127 x 10~ 6 calories or 



— 532 ergs. 



The discrepancy between the two results may well be attributed 

 to some slight difference of composition, for Riecke gives the 

 value + 24*5 x 10 -6 calories for commercial bismuth*. Moreover, 

 Le Rouxf in his comparative results obtains the same values 

 for bismuth and iron whilst Batelli finds for iron the value 



— 1130 ergs J. 



Alloy No. 1, containing 1*23 per cent, of tin. 



Mean diameter of rods = 4*85 mm. 



Mean resistance of rods = 0*00019 ohms per mm. 



One series of observations is shown in Tables III and IV from 

 which the value ov.g = — 11,700 is calculated. 



* Experimentalische Physik, ii. p. 345. 



t loc. cit. 



X loc. cit. p. 539. 



