[ 45 ' ] 
I fhall ask in my turn. How, in an iatire Tlenum, 
do heavy Bodies fall to the Centre J And I reafon on 
the Principle granted to Monfieur Fontenelle. 
But yet, becaufe what is allowed by one Cartejian 
is not always allowed by allj let us fuppofe, that the 
upper Layer cannot defeend j this, at leaft, will follow 
from my Demonftration, that, according to the Prin- 
ciples of all thefe Gentlemen, an upper Layer being 
preffed by all the under ones, it muft haften its Circu- 
lation, as long as it is flower than tliat of thefe under 
Layers; by reafon that the Excefs of their Velocities 
will aft upon it, as if it had been at Reft. 
Corollary IV. 
Therefore the Layers of a Vortex will movj. all of 
a Piece, as do thofe of a folid Sphere ; and Kepler % 
Law cannot poflibly be preferved. We fhall how 
give other Proofs upon other Principles. 
Theorem V. 
The Motion of the Points of the Equator is abf<> 
lutely independent of the Motion of the parallel 
Circles ; and confequently, in order to determine the 
ei/Equilibrium of the Points of the Equator, we muft 
attend to nothing but its Motion. 
Demonstration. 
The Plane of the Equator is parallel to the Planes 
of the other parallel Circles, that turn round the 
fame Axe with it: Its centrifugal Force is perpendi- 
cular to the Tangent to the Sphere, which anfwers to 
k : It has not then any lateral Tendency towards thefe 
parallel 
