264 Prof. J. J. Thomson and Mr J. Monckman, On the [June 4, 
The condition that the real and imaginary parts of one of 
the roots of (71) may vanish and change sign is that k,=0, k, 
being given by (68). In order that the system may be secularly 
stable, &, must be positive for all values of n except zero. 
This must be true even if n=1, for unlike (33) the equation 
(71) does not then split imto factors of which the roots are 
essentially positive. The condition of secular stability is therefore 
Qarey (o — p) Wa? — @ > 0 ......ccecenene (72), 
which when w?= 0 leads to the condition 
GC > Discos scene ues tee eee eee (73) 
It is well known that unless this is fulfilled the liquid will all 
collect on one side of the solid cylinder. 
(8) The Effect of Surface Tension on Chemical Action. By 
J.J. THomson, M.A., F.R.S., Cavendish Professor, and J. MoncK- 
MAN (D.Sc. Lond.), Downing College. 
In a paper on “Some Applications of Dynamics,” Phil. Trans. 
1887, Part I, see also Applications of Dynamics to Physics and 
Chemistry, p. 234, one of us has shown that when a number of 
dilute solutions of reagents are mixed and allowed to settle into 
equilibrium, then if « be the coefficient of the chemical action, 
z.e. the value in the state of equilibrium of 
ye"... 
Prt. 
where a, y, z are the masses of the substances which appear as 
the chemical action goes on, &, 7, € the masses of those which 
disappear, and a, 0, c... the electrochemical equivalents of the 
substances divided by their molecular weights: the value of « 
is altered by the action of the surface tension and the alteration 
is expressed by the equation 
SK £273 
PAG a Tm bag (8!) 
where £ is the molecular weight of the substance, whose mass is &, 
S the area of the surface exposed, 7’ the surface tension and @ the 
absolute temperature. Thus if SZ’ increases as & increases dx is 
positive, that is &, 7, € are diminished, or in other words the action 
of the surface tension tends to stop that chemical change which 
is accompanied by an increase in the value of SZ. This is the 
