CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL LABORATORY, 



HARVARD COLLEGE. 



ON THE THOMSON EFFECT AND THE TEMPERATURE 

 COEFFICIENT OF THERMAL CONDUCTIVITY IN SOFT 

 IRON BETWEEN 115° AND 204° C. 



By Edwin H. Hall, L. L. Campbell, S. B. Sebviss, and 



E. P. Chckchill.1 



Presented May 9, 1906. Received December 7, 1906. 



Introduction and Summary of Results. 



A PAPER printed in these Proceedings for May, 1905, by the authors 

 of the present paper gave the following results as obtained from the 

 study of a certain specimen ^ of soft iron : 



Composition : iron, 99.93% ; carbon, 0.059%. 



Density : about 7.785 at 0° C. 



Thermal conductivity, k : 0.1528 at 28.2° C, 



with a temperature coefficient 0.0003 (1) from 28° to 58°, 

 " " " " 0.0007 0) " 13° " 87°, 



the latter value being the more reliable. 

 Electric resistance, absolute : 11365 at 0° C, 



with a mean temperature coefficient 0.00519 from 0° to 100°. 

 " Thermo-electric height " with copper : 



1028 X 10-8 volt at 26.6° C, 

 980 " " " 41.3° C, 

 936 " " " 54.5° C, 



. 870 " " " 71.1° C, 



'^ Mr. Churchill was not engaged in the earlier part of the work described in 

 this paper, but he worked with me during the greater part of July, 190(3, in a 

 supplementary investigation. — E. H. H. 



^ It is proverbial that the various properties of any given metal, as set down 

 in plij'sical tables, are usually obtained from different specimens. It has seemed 

 to us worth while to study one particular kind of iron in as many of its different 

 aspects as practicable. The study is still in progress. 



approximately 



