THE 
LONDON ano EDINBURGH 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
[THIRD SERIES.] 
FEBRUARY 1836. 
XVI. On Capillary Attraction and the Molecular Forces of 
Fluids. By the Rev. James CHAuts.* 
i Laplace’s capillary theory the fluid is supposed to be 
perfectly incompressible ; and the only forces acting on it 
besides gravity, are assumed to proceed both from its own 
molecules and those of the solid with which it is in contact, 
to be wholly attractive, and to become insensible at all sensi- 
ble distances from the attracting centres. Calculations made 
on these hypotheses serve to explain phenomena in a remark- 
able manner. But the principles of this theory are liable to 
objection, as no account is taken of a repulsive molecular ac- 
tion, whilst, on the supposition of a molecular constitution of 
the fluid, the particles could not be held in places of equili- 
brium but by the action of repulsive as well as attractive 
forces. ‘The theory of M. Poisson not only meets this ob- 
jection by regarding the fluid as composed of insulated mo~ 
lecules subject to the opposite tendencies of attractive and 
repulsive forces, and as liabie to compression, but takes into 
consideration also the effect of the variation of density, which, 
according to this constitution of the fluid, must exist within 
a small depth both from its free surface and from that in 
contact with the solid. This, no doubt, is the only complete 
method of treating the problem. The next inquiry is, to 
what degree is that superficial variation of density effective? 
M. Poisson’s theory does not bear on this point, and experi- 
* Communicated by the Author. 
Third Series. Vol. 8. No. 45. Feb. 1836. N 
