1168 



formula ^) — which expresses the difference as a quadratic function 

 of (1 — w^,) — can be used down to 



1 — «'„ = ca. 0.92 



T^ca. 50° K. 



1) F. Henning, Ann. d. Fhys. 40 (1913), p. 635 seqq. 

 A = M {w— 1) + N {w— 1 )* 



(1) 



