KING. 



MEASUREMENT OP THOMSON EFFECT IN COPPER. 



371 



The values of the Thomson Effect deduced above decrease with an 

 increase of temperature. This is, of course, contrary to the accepted 

 view. It is, then, important to determine to what extent the necessary 

 errors of tlie method used affect the result. 



It is probably apparent to the reader that the most serious errors are 

 likely to be found in the estimation of the thermal conductivity and in 

 the determination of the h curve. As already explained, on account of 

 the shortness of the experimental bar a large correction has to be applied 

 for the conduction of heat from the middle section of the bar in the 

 determination of the h curve. However, this correction is not so large 

 that a considerable error in the estimation of the thermal conductivity 

 would affect the value of the h curve within the limits of accuracy of 

 this work. 



The form of the h curve, f ff, Fig. 3, was unexpected. It was thought 

 that it would be either straight or bent downwards at the higher temper- 

 atures. In some experiments made two years ago at McGill University, 

 a number of " h curves " were obtained for bars under similar conditions 

 and in all cases they were very nearly straight. Taking, then, the 

 dotted line//, Fig. 3, to be the h curve, and taking its inclination from 

 the lower points, the portion of the Thomson Effect determination 

 affected by this change has been reworked. The results are given in 

 column II. of the following table. 



