1294 
In the notation of Voigt we have A=3}c,, , B=— 2e. 
If the temperature is high enough for the theorem of equipartition 
to be true, then 
&égi— He and eg = he 
where # is the total energy. 
For the thermal pressure we then find 
a! 9C+2D 3D+E 
— S=>— {|——— + ——}éeé .,.. . (20 
Ty nee Coe 
We shall also use (20) for very low temperatures. According to 
Born *) the proportion of the energy of the longitudinal and trans- 
versal waves can be put in the form 
er 
wags os 
Vl Utr 
Eg 1 > Egan — 
where v, and wv, are the velocity of propagation of these waves. 
Introducing the constants c,, and c,,, we thus have 
y | 
PR ek TE 
Putting the total energy e, we find 
8/. 3/ 
St of} Ye Oor 
eras RRL SOE ga EE 
2 c4a + deur 2 ca4 + 4e 
and finally 
9 Sa 5] 
3 (Be + $D) cag — (ED + FE) c11 : 
a} 9). 3) 
C44C,, (Cad + Zer 
This special result agrees with the expression found by VAN 
EVERDINGEN ?). The theorem of GRÜNEISEN can be immediately deduced 
from it. 
The influence of temperature on the elastic constants can be 
examined in the same way, as we shall show in the third contribution. 
(205) 
Utrecht, Febr. 1916. Institute for mathematical physics. 
1) Born l.c. p. 75. 
2) VAN EVERDINGEN, l.c. p. 24 form (20) p. 53 form (87). 
