280 
selves as far as these deviations are concerned according to the more 
or less complicated structure of their molecules. The curves for VII. 1 
in the region of reduced temperature to which the diagrams refer 
are obtained chiefly from isopentane and ether, substances which 
have very complex molecules; after these come, in the order given, 
carbon dioxide, with an undoubtedly less complex molecule, and 
finally argon. Clearly, just as was the case with the deviations which 
were encountered in a previous paper’), one must look for the 
explanation of this in a real or apparent compressibility which 
diminishes in magnitude as the molecule becomes less complex in 
shape or structure, or in a characteristic behaviour of the attraction 
potential determined by this peculiarity. 
We hope to present further communications shortly giving results 
of calculations of various thermodynamical quantities which may be 
made from the equation now given within the limited region for 
which it holds. 
1) Proc. July 1911. Comm. NP. 1210. 
(September 2, 1912). 
