( 204 ) 



Messrs. KoilNsTAMM ;iii(l OuNSTKiN Would ever lliiiik of applviii^i- v.vN 

 DKH Waals' formula lo aiuorplioiis (^luii'z, and siinilai' suhslaiices. 

 For here there is no loii<ier present unchecked movement of the 

 molecules, and this is entirely in conflict with the premises on 

 which VAN DKK Waals' tornuila was derived. Indeed, the new theorem 

 of heat is intended to account for the entirely different circumstances 

 found here; for the rest it necessarily follows from the theory of 

 indivisible units of energy ^). 



Messrs. Kohnsta.alm and Oknsthin therefore try to refute my theo- 

 retical consideration- l»y evidently inaccurate, nay even inadmissililc 

 formulae "). 



It is known that when Tait (piestioned the second theorem of 

 heat on the assumption of Demons, Clausius could point out with 

 perfect justice that his formulae did not refer to the question how 

 heat behaved with the aid of Demons, but what it did of its 

 own accoi'd. In the ^ame way the attention of Messrs. Kohnstamm 

 and Ohnstkln nnglit be drawn to the fact that equation ^2) does not 

 hold for substances which oidy exist in their imagination, and that 

 the real behaviour of substances at low temperatures should be 

 laken into account. 



In conclusion we may point out that the formulae (2) express the 

 whole of ni} theorem of heat, and that particularly the applications 

 which I have n)ade to (jtiseous systems, with which remarkably 

 enough, the authors exclusively operate, consist oidy in a combina- 

 tion of these formulae and the already known theorems of heat. 



Physics. — ''Further EiperiinerU.'i todh Liquid IIcHuiil. E. .1 Udiuni- 

 (Jrijostat. Ri'iiuirks on the [)recu'dLiig (Join inuniaitions." By Prof. 

 H. Kamerlingii OxNNKS. Oomm. N". 123" from the Physical 

 ijaboratory at Leiden. 



§ i. introduction. In the Jubilee volume presented in October 

 1910 to J. M. VAN Bemme],en a description was given of an arran- 

 gement by means of which liquid helium had been successfully 

 transferred from the apparatus in which it had been prepared to 

 another vessel in which the measuring apparatus could be immersed 

 in liquid helium. Advantage was then taken of this arrangement to 



1) Nernst, Journ. de Chim. Phys, 8 234 (1910); F. JütTxXer, Zeitschr. I'. Elek- 

 trochem. 17 139 (1911); 0. ÖacküR, Ami. d. Phys [4] 34 455 (1911). 



•) With an analogous reasoning the said authors might also have "refuted" 

 Pla.nck's ioiniula of radiation, the whole theory of indivisible units of energy etc. 



