424 
PROFESSOR C. H. LEES: THERMAL AND ELECTRICAL 
The results of the observations are embodied in the curves on the opposite page. 
From the smooth curves drawn as nearly as possible through the points given by 
the observations, the table on p. 426 of values of the conductivities at various 
temperatures has been constructed. 
Discussion of the Thermal Conductivity Results. 
An inspection of the curves of results over the temperature range —170° C. to 
+ 30° C., to which for comparison the results obtained by Jager and Diesselhorst* 
at 18° C. and 100° C. have been added, shows that over the whole range from 
—170° C. to +100° C. the thermal conductivity of a pure metal changes comparatively 
little. As to the character and magnitude of the small rates of change of conductivity 
with temperature at 18° C., the two sets of experiments are in close agreement 
throughout. As the temperature rises there is a slight decrease in the conductivity 
of zinc, copper, iron, cadmium, tin, and lead over the range covered by the 
experiments. The absolute values of the conductivity at 18° C., given by the present 
experiments, agree closely with those given for these metals at this temperature by 
Jager and Dfesselhorst, except in the case of cadmium, for which the present 
value of k at 18° C. is about 2 per cent, less than that obtained by Jager and 
Diesselhorst. Silver appears to have a maximum conductivity at about —90° C., 
and to decrease very slightly in conductivity up to + 100° C. The value of k at 18° C., 
according to the present experiments, is about 3 per cent, less than that of Jager 
and Diesselhorst. Steel shows a slight tendency to a maximum about —50° C., 
the change with temperature at 18° C. agreeing with that found by Jager and 
Diesselhorst, although the absolute value at 18 c C. is about 5 per cent, higher than 
for their steel. Aluminium has a minimum conductivity about —110° C., and a 
rate of change with temperature about 18° C., which agrees with that found by,* 
Jager and Diesselhorst, although the absolute value is about 4 per cent, higher 
than theirs. 
The alloys tested all increase in conductivity with increase of temperature. In the 
case of manganine the absolute value and the rate of increase with temperature at 
18° C. agree with those given by Jager and Diesselhorst. 
W1 len the slight unavoidable differences in purity of the specimens used by Jager 
and Diesselhorst and by myself are taken into account, the close agreement between 
the results obtained by methods which differ so materially from each other must be 
considered most satisfactory, for not only have we possible differences in chemical 
composition to contend with, but, according to the researches of Beilby,! for each 
* W. Jager and II. Diesselhorst, ‘ Wissenschaftl. Abhandl. d. Phys.-Techn. Reichsanstalt,’ 3, p. 270, 
(1900). In cases where they give two or more values for the same metal, that value has been used to 
which they attach the greatest weight. 
t ‘ Phil. Mag.,’ 8, p. 258 (1904); ‘ Roy. Soc. Proc.,’ A, 76, p. 462 (1906), and 79, p. 463 (1907). 
