[ 4P 3 
parallel Circles, and by a neceffary Confequencc its 
Motion is abfolutely independent of theirs. 
And indeed, if it be fuppofed, that the Motion of 
the other parallel Circles flops, there is flill fome 
Motion conceived in the Equator, juft as in the Cafe 
of the cylindrical Vortex : It is likewife conceivable, 
that the Velocity may be greater at the Equator than 
in the parallel Circles, as the Experiment already 
cited fhews us: And if no Regard be had to the 
lateral Fridions, as xhtCartefians would have it, who 
fuppofe them none or infenlible, and as indeed they 
are obliged to fay, that the Vortex^ by the lateral 
Fridion of the Equator, may not become cylin- 
drical j this Equator will always continue to circulate 
uniformly, without communicating any of its Ve- 
locity to the Points that laterally furround it. There- 
fore, ^E. T>. 
Corollary I. 
Therefore for the (^^Equilibrium of the Points of 
the Equator, it is neceffary, at leaft, that an upper 
Circumference fhould have as much Tendency to- 
wards the Superficies of the Vortex^ as another under 
concentric Circumference; becaufe, if it had lefs, 
there would be no <i_yEquilibriumy even in the Prin- 
ciples of the Cartejiansi and the under Circum- 
ference, prefling the upper, would either make it 
defeend, or communicate to it a Force equal to its 
own. Wherefore, calling F the proper centrifugal 
Force of a Point of the upper Circumference, zndf 
that of a Point of the under one ,* if S, s mark the 
different Sums of the Points contained in thefe Two 
Circumferences, we fhall have F S = fs. 
Co- 
