648 
not to be regarded as wholly bad, so that at the lower temperatures 
(below — 100° ©.) the experimental results at present available for 
helium are, as far as B is concerned, compatible with the assumption 
of rigid spheres of central structure with an attraction potential 
proportional to — 7 + 
Having now reached the end of the considerations advanced in 
Suppl. N°. 24, 25, and 26 it is my pleasant duty to thank Prof. 
KAMERLINGH ONNEs for having invited me to participate in the inves- 
tigation of the second virial coefficient for gases of low critical 
temperature, which he had undertaken with the object of reaching 
some conclusion regarding the structure and mode of action of the 
molecule, in particular with the help afforded by the application 
of BorrzMaNN’s principles, and also for his kindness in leaving to 
me the continuation of the investigation within the particular region 
which I have treated in this series of papers. 
