Vol.. 6, 1920 
PHYSICS: E. H. HALL 
139 
2 Cohen, B. and Smith, A. H., /. Biol. Chem., 39, 1919 (489). 
3 Cf. Fisher, G. and Wishart, M. B., /. Biol. Chem., 13, 1912 (49). 
* A part of the expenses of the work herein reported has been defrayed from the 
Francis B. Loomis Research Fund of the Yale University School of Medicine. More 
extensive reports will be sent to the Journal of Pharmacology & Experimental Thera- 
peutics and to the Archives of Internal Medicine. 
INFERENCES FROM THE HYPOTHESIS OF DUAL ELECTRIC 
CONDUCTION; THE THOMSON EFFECT 
By Edwin H. Hai^i^ 
JEPPBRSON Physicai. Laboratory, Harvard University 
Communicated January 29, 1920 
At the Washington meeting of the National Academy of Sciences in 
April, 1919, I presented two papers that have not yet been published. 
One was on the Effect of Pressure on Electric Resistance and on Peltier 
Heat in Metals, the other on Thermal Conduction in Metals, both being 
written from the standpoint of Dual Electric Conduction. 
The first named of these two papers contained implicitly the following 
propositions : 
la. Increase of pressure should, by bringing the atoms and the metal 
ions closer together, increase ka, the associated-electron conductivity, 
and decrease kf, the free-electron conductivity. We might, then, ex- 
pect the total conductivity, k, to increase under pressure in metals having 
a relatively small value of {kf -^ ka) and to decrease in metals having 
a relatively large value of this ratio. 
16. As antimony and bismuth have exceptionally small values of k, 
they probably have exceptionally large values of {kf ka), and this may 
account for the fact that, among twenty metals examined by Bridgman, 
these two were the only ones to show a decrease of conductivity under an 
increase of pressure. 
2a. If the ratio {kf ka) is greater in metal B than in metal A, ioniza- 
tion must occur at the junction of the two metals when a current flows 
from A to B, and re-association must occur there when the current flows 
from B to A. As ionization is doubtless accompanied by absorption of 
heat and re-association by evolution of heat, we have here an action which 
may play a very important part, if not the chief part, in the Peltier effect. 
2b. The exceptionally large value of {kf ka) that probably exists 
in bismuth may account for the fact that heat is absorbed when a nega- 
tive current goes into this metal from any other. 
2c. As increase of pressure probably decreases the ratio {kf -7- ka), 
we should expect an absorption of heat where a negative current flows 
from a metal under high pressure to the same metal uncompressed. If 
we call this efi"ect of compression plus and the opposite effect minus, we 
