Vol. 6, 1920 
PHYSICS: E. H. HALL 
613 
THE THOMSON EFFECT AND THERMAL CONDUCTION IN 
METALS 
By Edwin H. HalIv 
Jkfferson Phy.sical Laboratory, Harvard University 
Communicated July 14, 1920 
The Thomson Effect. — In these Proceedings for March, 1920, is a paper 
in which I undertook to account for the Thomson effect values, as found 
by Bridgman for many metals, in accordance with the hypothesis of dual 
electric conduction. 
Using data obtained by the methods of that paper, I was able, as I 
stated at the Washington meeting of the National Academy in April, 
1920, to account quantitatively for the values of thermal conductivity 
found in a large number of metals at room temperature. I stated further, 
however, that the temperature-coefficient of thermal conductivity indi- 
cated by my calculations was far too large to accord with the obvious 
facts, and that a revision of my formulae was therefore necessary. This 
revision, which has now been made, enables me to deal pretty satisfac- 
torily with thermal conduction, if my assumptions are granted. It in- 
volves important changes in most of the numerical tables in the paper 
referred to, but no great change in the method there followed. 
The revision begins with equation (11), which is changed by the sub- 
stitution of 5 for 2.5, so that it now stands 
X' = \'o + sRT, (1) 
where 5 is a constant, which varies from one nietal to another but is 
always greater than 2.5. The X' of this equation is the number of ergs 
required to separate one electron from its atomic union and leave it free, 
as a gas particle, within a metal; X'o is a constant which may be different 
in different metals, and R is the gas constant for a single molecule. The 
assumption involv^ed in this equation, like some others I have made, may 
seem improbable; but, as it does not, so far as I am aware, conflict with 
established facts or principles, ^ and as it serves my purpose fairly well, I 
have felt justified in adopting it provisionally. 
As the total energy which a free electron possesses in virtue of its 
character as a monatomic gas molecule is 2.5 RT, the kinetic energy 
and the pv energy being taken together, and as I assume that this energy 
is acquired in the act of ionization, I have 
X' - 2.bRT, or X'o + - 2.b)RT, 
as the number of ergs required for overcoming the attractions or repul- 
sions which are operative in the act of freeing a single electron from an 
atom, under the conditions which prevail within a solid metal. The 
