of Edinburgh, Session 1879-80. 
405 
Monday , l§th January 1880. 
Professor H. C. FLEEMING JENKIN, Vice-President, 
in the Chair. 
The following Communications were read and Business 
transacted : — 
1. Part of the Material employed by Principal Forbes in 
Tamping the Bore for his Earth Thermometers at the 
Edinburgh Observatory was exhibited in its altered state. 
2. A New Method of investigating Relations between Functions 
of the Roots of an Equation, and its Coefficients. By 
J. D. H. Dickson, M.A. 
3. Remarks on Mr Crookes’s Recent Experiments. 
By Professor George Forbes. 
The author explained that he was glad to be able to bring before 
the Society some apparatus illustrative of Dr Crookes’s splendid 
researches on what he calls radiant matter. This he was able to do 
by the skill of Mr Gimingham, who had prepared some splendid 
vacuum tubes for him lately. He valued those researches very 
highly, because they brought most conclusive evidence to bear upon 
the truth of the kinetic theory of gases ; because they gave us a 
clear insight into the action of the electric current and discharge ; 
because they promise to help us in forming a notion of what electri- 
city really is ; and because we may also hope from these researches 
to get some knowledge of the nature of molecules. 
It is now generally conceded that a gas consists of detached 
molecules, moving about with great rapidity, and rebounding from 
each other and from the sides of the containing vessel, with perfect 
elasticity; Clausius and Maxwell have shown that at any given 
pressure the molecules on an average can travel over only a certain 
