895 
Congress of Science and Medicine at Groningen (1911) *). An invest- 
igation regarding the specific heat of lead, after which other metals 
were to follow, at hydrogen temperatures, an investigation which 
had a particular interest with a view to Erstnin’s theory and also 
in connection with ?) Nernst’s theorem, was announced on that occasion. 
Since then in Nernst’s laboratory a highly important series of 
investigations on the specific heat bas been made by himself and 
by his collaborators *). In particular the investigations on solids at 
low temperatures, which had already been made down to the tem- 
peratures of liquid air boiling under reduced pressure, were continued 
to the temperatures which can be obtained with liquid hydrogen. 
Besides KAMERLINGH ONNES and Horst‘) made preliminary measure- 
ments of the specific heat of mercury at helium temperatures. The 
investigations menticned have already furnished a great number of 
highly valuable data, which in particular have served for a test of 
the theories of Desire’) and of Born and v. K ARMAN *). The method 
„we followed is mainly that which has been developed by Nernst 
and Evcken. Notwitbstanding all that the continuation of our programme 
seemed to remain desirable. First, when Nrrnst’s investigations had 
followed the specifie heat down to the region of hydrogen temperatures, 
because only a few of his observations entered into this region and 
the accuracy of the observations left some doubt with Nernst himself, 
and later, when between the boiling point and the melting point 
of hydrogen also more accurate determinations had been made in 
his laboratory 7), because for the investigation of the questions which 
1) W. H. Keesom. The heat of vaporisation of hydrogen. Handel. 13de Ned. 
Nat. en Geneesk. Congres, April 1911, p. 181. Publishedalso Leiden Gomm. N?.137e. 
2) Cf. also H. Kamertincu Onnes. Reports of the IInd International Congress of 
Refrigeration. Vienna 1910 (Comm. Leiden Suppl. N°. 210 p. 42). 
3) For the literature we refer to Leiden Comm. Suppl. N°. 23 “Die Zustands- 
gleichung” Math. Encycl. V. 10 Note 838. Later: A. Euckrn and I. ScHWERsS. 
Verh. d. D. phys. Ges. 15 (1913) p. 578, W. Nernst and F. Schwers. Berlin 
Akad. Sitz. Ber. 1914 p. 355. R. Ewatp Ann. d. Phys. (4) 44 (1914) p. 1213. 
4) H. KAMERLINGH ONNEs and G. Horsr. Comm. NO. 142c (Sept. 14). 
5) P. Deprye. Ann. d. Phys. (4) 39 (1912), p. 789. W. Nernst and F. A. LINDEMANN 
Berlin Akad. Sitz. Ber. 1912, p. 1160. Cf. also W. Nernst, Vorträge Wolfskehl 
Congress Göttingen 1913, p. 61. 
6) M. Born and Tu. v. Karman. Physik. ZS. 13 (1912), p. 297 ; 14 (1913), p. 15, 
65. H. Tarrrine, Physik. ZS. 14 (1913), p. 867; 15 (1914), p. 127, 180. Cf. 
M. Born, Ann. d. Phys. (4) 44 (1914), p. 605. 
7) A part of our observations had already been made when the results of 
Evcxen and Scuwers were published (see § 5). The completion of even the limited 
part of the programme, which is contained in this communication, has been much 
retarded, partly by the wish to attain very trustworthy results, 
