KING. — MEASUREMENT OF THOMSON EFFECT IN COPPER. 377 



These results for the Thomson Effect seem to be considerably better 

 than the first ones found with a heating current of 30 amperes. The 

 value obtained for the shortest section and highest temperature is still 

 a little larger than the one immediately preceding it ; but it is a good 

 deal smaller than the value found for the lowest temperature. 



In order to see what effect a diflferent value of the thermal conduc- 

 tivity would have on the character of the results as regards variation 

 with temperature, the observations for the first experiment with 30 

 amperes have been worked through, using Stewart's value of the ther- 

 mal conductivity. The modified results are given in column II. below. 

 The original results, for the sake of comparison, of the first and second 

 experiments are given in columns I. and III. respectively. 



Comparison of the Experiments at 80 and 35 Amperes. 



It is seen from the above results that the change made in the ther- 

 mal conductivity has had the effect of increasing the diminution of the 

 value of the Thomson Effect with a rise in temperature. The results 

 of the two experiments with 30 amperes are not so consistent and 

 regular as could be wished, yet it must be remembered that the reduc- 

 tion of the heating current from 35 to 30 amperes has probably lessened 

 the accuracy of the work 50%. Taking from the experiment with 35 

 amperes the value of the Thomson Effect obtained with the largest 

 number of sections, we have o- = .00000608 at 166° C. From the first 

 experiment with 30 amperes we have o- = .00000628 at 122° C. 

 These values agree fairly well, but exemplify the diminution of the 

 Thomson Effect with a rise in temperature. From two experiments 

 conducted on different parts of the experimental bar and with all the 

 important quantities, such as temperature gradients etc., so different, it 



