73 
on the Cohesion of Fluids . 
corresponding proportion for the ascent of the acid in a capil- 
lary tube, and which does not very materially differ from the 
proportion of .395 to 1, assigned by Barruel for this ascent. 
Musschenbroek found it .8 to 1, but his acid was probably 
weak. For alcohol the adhesion was as .593, the height as 
.715, and its square as .510 : the observed proportion in a tube, 
according to an experiment of Musschenbroek, was about 
.550, according to Carre' from .400 to .440. The experiments 
on sulfuric ether do not agree quite so well, but its quality is 
liable to very considerable variations. Dutour found the 
adhesion of alcohol .58, that of water being 1. 
With respect to mercury, it has been shown by Professor 
Casbois of Metz, and by others, that its depression in tubes 
of glass depends on the imperfection of the contact, and that 
when it has been boiled in the tube often enough to expel all 
foreign particles, the surface may even become concave instead 
of convex, and the depression be converted into an elevation. 
But in barometers, constructed according to the usual methods, 
the angle of the mercury will be found to differ little from 
140°; and in other experiments, when proper precautions are 
taken, the inclination will be nearly the same. The determi- 
nation of this angle is necessary for finding the appropriate 
rectangle for the curvature of the surface of mercury, together 
with the observations of the quantity of depression in tubes of 
a given diameter. The table published by Mr. Cavendish from 
the experiments of his father, Lord Charles Cavendish, ap- 
pears to be best suited for this purpose. I have constructed a 
diagram, according to the principles already laid down, for 
each case, and I find that the rectangle which agrees best with 
the phenomena is .01. The mean depression is always .015, 
mdcccv, L 
