of a homogeneous fluid mass that revolves upon an axis. 117 
it lies, by the respective gravitations. If we conceive a curve 
line GHLOR, extending from the common centre G so as 
to cut all the similar surfaces at right angles ; that curve 
line will mark the directions both of the gravitation and the 
pressure of the fluid in the interior of the body RST. Where- 
fore the several surfaces OPQ, LMN, &c. are no other than 
the level surfaces of the body RST in equilibrio ; and each 
of these surfaces will be pressed by the superincumbent fluid 
with the same intensity over its whole extent. 
But at the same time that the uppermost stratum presses 
upon the fluid below it, by the gravitation at the surface OPQ, 
it likewise attracts every particle of matter within the same 
surface. And, in like manner, every successive stratum both 
presses on the surface on which it lies by the gravitation at 
that surfafce, and attracts all the particles within it. Where- 
fore the body H I K is not only pressed by the superincum- 
bent fluid, but every particle of it, is likewise attracted by all 
the exterior matter. These forces are independent on one 
another. Although the body H I K be in equilibrio with re- 
spect to the pressure it sustains, it does not follow that it will 
likewise be in equilibrio with respect to the attraction which 
the exterior matter exerts upon it. In order that this latter 
equilibrium take place, it is necessary that every stratum of 
the exterior matter be possessed of such a figure as to attract 
all particles in the inside with equal force in opposite direc- 
tions. 
We have now proved that, if the fluid mass RST be in 
equilibrio, the interior body H I K will likewise be in equi- 
librio when it revolves by itself, the exterior matter being 
taken away, or annihilated ; which cannot be the case, unless 
