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III, Essay on the Cohesion of Fluids. By Thomas Young, 
M, D. For. Sec. R. S. 
Read December 20, 1804,. 
I. General Principles. 
It has already been asserted, by Mr. Monge and others, that 
the phenomena of capillary tubes are referable to the cohesive 
attraction of the superficial particles only of the fluids em- 
ployed, and that the surfaces must consequently be formed 
into curves of the nature of linteariae, which are supposed to be 
the results of a uniform tension of a surface, resisting the 
pressure of a fluid, either uniform, or varying according to a 
given law. Segner, who appears to have been the first that 
maintained a similar opinion, has shown in what manner the 
principle may be deduced from the doctrine of attraction, but 
his demonstration is complicated, and not perfectly satisfactory; 
and in applying the law to the forms of drops, he has neglected 
to consider the very material effects of the double curvature, 
which is evidently the cause of the want of a perfect coinci- 
dence of some of his experiments with his theory. Since the 
time of Segner, little has been done in investigating accurately 
and in detail the various consequences of the principle. 
It will perhaps be most agreeable to the experimental phi- 
losopher, although less consistent with the strict course of 
logical argument, to proceed in the first place to the comparison 
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