EESISTANCE OF NICKEL. 



327 



the various metals. The accompanying temperature scale is of course 

 only approximate. 



Temperature 



(Centigrade.) 



Resistances (with Differences). 1 



Platinum. 



Palladium. 



Iron. 



Nickel. 



0° 



10 3 



10 5 



10 s 



10 5.2 



140 



13 3 



15 5.1 



18 10.. 



15.2 ,B 



280 



16 3 



20.1 ,« 



28.4 1,1 



23.5 e, 



420 



19 3 



24.9 , 



42.5 ,,3 



29.7 ,1 



560 



22 



28.9 



63.3 



33.8 



Further experiments with the nickel were made in which 

 resistance changes and thermoelectric changes were measured simulta- 

 neously ; and these completely established the fact that the two 

 peculiarities occur at the same temperature. The final conclusions 

 are these. (1) At about 200° C. the rate of resistance growth for 

 nickel increases markedly, and continues practically steady, till about 

 320° C, when a sudden decrease occurs, and thereafter the resistance 

 steadily increases at this diminished rate. In other words, between 

 the limits of temperature specified, the slope of the resistance curve is 

 much steeper than anywhere else. The same peculiarity is probably 

 possessed by iron between the temperatures of a dull red and a bright 

 red heat. (2) The peculiarity occurs (in each case) between the 

 limits of temperature within which the striking thermoelectric 

 peculiarity discovered by Tait also occurs. This peculiarity, which 

 is most briefly described as an abrupt change in the sign of the 

 Thomson Effect, is not known to be possessed by any other metal. 

 (3) There is thus a strong presumption that the Thomson Effect in 

 metals has a close connection with the mutual relations of resistance 

 and temperature — at any rate in metals in which the Thomson Effect 

 is proportional to the absolute temperature (according to Tait's theory) 



