2 6 
Mr. Vince's Observations on the Theory 
errors, except that which is founded upon such experiments as 
include in them the consequences of all those principles which 
are liable to any degree of uncertainty. 
A fluid being composed of an indefinite number of cor- 
puscles, we must consider its action, either as the joint action 
of all the corpuscles, estimated as so many distinct bodies, or 
we must consider the action of the whole as a mass, or as one 
body. In the former case, the motion of the particles being 
subject to no regularity, or at least to none that can be disco- 
vered by any experiments, it is impossible from this considera- 
tion to compute the effects ; for no calculation of effects can be 
applied when produced by causes which are subject to no law. 
And in the latter case, the effects of the action of one body 
upon another differ so much, in many respects, from what would 
be its action as a solid body, that a computation of its effects 
can by no means be deduced from the same principles. In 
mechanics no equilibrium can take place between two bodies 
of different weights, unless the lighter acts at some mechanical 
advantage ; but in hydrostatics, a very small weight of fluid 
may, without its acting at any mechanical advantage what- 
ever, be made to balance a weight of any magnitude. In me- 
chanics, bodies act only in the direction of gravity ; but the 
property which fluids have of acting equally in all directions, 
produces effects of such an extraordinary nature as to surpass 
the power of investigation. The indefinitely small corpuscles 
of which a fluid is composed, probably possess the same powers, 
and would be subject to the same laws of motion, as bodies of 
finite magnitude, could any two of them act upon each other 
by contact ; but this is a circumstance which certainly never 
takes place in any of the aerial fluids, and probably not in any 
