356 
DR. E. H. GRIFFITHS AND MR. EZER GRIFFITHS ON THE 
the typical term in the expression for the atomic heat varies as 
W l 
e a +<9 0 3 J 
where 0 O is some definite temperature. 
We have been unable to find any value of 6 0 which would reconcile the locus of 
this curve with our data. 
Summary. 
1. In Part I. a description is given of a new method of maintaining an enclosure at 
any required temperature from that of the room down to about —165° C., by a direct 
application of the Joule-Thomson cooling effect on expansion of air. 
2. Specific heat determinations have been made at various points in the above range 
for Al, Cu, Zn, Ag, Cd, Pb, Fe, and Na, and data obtained for these metals which 
determine the loci of the atomic heat temperature curves from about 120 C. abs. to 
400° C. abs. 
3. It is shown that in the case of silver and lead there is no difference greater 
than the probable errors of experiment between the values obtained by Neenst and 
those given by the methods described in this paper. Hence, for Al, Cu, Zn, Ag, and 
Pb it is possible to extend the atomic heat curves by means of the data given by 
Nernst for these metals at the temperatures of liquid air and hydrogen. 
4. The most probable values of the atomic heat at various temperatures are 
tabulated in Table XV.„ together with the calculated difference between C p and C„. 
5. In Part II. a brief review is given of the various theoretical formulae and the 
assumptions upon which they are based. 
6. It is shown that none of the formulae are capable of representing the 
experimental results over the entire range of temperature. 
The formula of Debye appears to give the nearest approximation to the 
experimental values over the lowest portion of the range, but systematic divergences 
occur at the higher temperatures. This may be due either to the assumptions made 
by Debye being valid only at very low temperatures, or that additional heat energy 
to that involved in the three degrees of freedom, ascribed to the atom, must be taken 
into account. 
