of a homogeneous fluid mass that revolves upon an axis. 1 1 1 
outside of the stratum. With regard to the matter in the 
inside, a parallelopiped will act upon it effectively ; but, the 
united attraction of all the parallelopipeds in the same stra- 
tum upon every interior particle being equal in opposite 
directions, it will not disturb the equilibrium of the fluid be- 
low the stratum. Therefore, when we take into account all 
the forces that act upon the parallelopipeds ; both those 
urging them externally, and those inherent in their own 
matter ; it is evident, that all the molecules in the same level 
stratum will be in equilibrio with respect to the matter above 
them, and that they will press equably upon the fluid body 
below them, by the action of the gravity alone. The fluid 
mass will therefore be in equilibrio with respect to all the 
forces in action. Thus, in every view of the problem, it ap- 
pears that, when nothing essential is omitted, the particular 
conformation of the level strata which annihilates their action 
upon particles in the inside, is just as necessary to the equili- 
brium of the fluid mass, as the equality between the pressure 
and the effect of the accelerating forces. 
There is another way of arriving at the same conclusion, 
which, in reality, first led to the suspicion of some defect 
lurking in the usual determination of the equilibrium of a fluid 
mass. This new view of the subject, which applies only to 
the law of attraction that takes place in nature, is contained 
in the two following propositions. 
Proposition I. 
If a homogeneous fluid body revolving about an axis, be 
in equilibrio by the attraction of its particles in the inverse 
proportion of the square of the distance ; any other mass of 
