928 
physicists, is evident from a paper published by E. H. Grirriras 
and Ezer Grirritus'), who say: “a further possible source of uncer- 
tainty is the effect of sudden chilling of a metal when rapidly cooled 
from a high temperature. However they do not mention the reasons 
which led them to this conclusion. 
As these investigations as well as those of Ezer Grirritus ?) on 
“The variation with temperature of the specific Heat of Sodium in 
the Solid and Liquid State’, play an important rôle in our subsequent 
arguments, we must dwell upon them. 
Using a special calorimeter in which the metal was electrically 
heated, they determined the true specific heat of different metals (Cu, 
Ag, Zn, Sn, Pb, Al and Cd®) at different temperatures. As the 
substances were raised from a given temperature through very small 
ranges of temperature (about 1.4° C.) their previous thermal history 
was not changed by the experiment itself. Evidently this is of high 
importance, as in the methods in use up to the present (method of 
mixtures, ice-calorimeter) the substances are heated to considerably 
higher temperatures by which procedure changes may occur which 
are uncontrollable. 
6. The metals experimented with were of high purity. In this 
way Messrs. GrirritHs succeeded in determining for a certain piece 
of metal at a definite temperature values of the specific heat which 
were quite reproducible while the conditions of the experiments were 
changed within wide limits. For a certain piece of copper, the 
previous thermal history of which was however indefinite, they 
found. at-0> 6: 
Mean of 5 independent determinations 0.09094 (probable experi- 
mental error of the group 0.01 percent). 
Mean of 5 independent determinations 0.09079 (probable experi- 
mental error of the group 0.03 percent). 
Mean of 4 independent determinations 0.09098 (probable experi. 
mental error of the group 0.05 percent). | 
Mean of 4 independent determinations 0.09088 (probable experi- 
mental error of the group 0.08 percent). 
7. The metals used by the authors were cast. Evidently they 
were of opinion that the condition of their material was definite. 
This is most surprising, as they themselves called attention to the 
1) Phil. Trans. Roy. Soc. London 213 (A), 119 (1914), 
2?) Proc. Roy. Soc. London 89, (A) 561 (1914), 
8) And Iron. 
