'( ^ 4 ° ) 
6t It is to be here obferv’d, that if a Body doth freely 
< c revolve in a Circle about a Center, as the Planets do- 
<• about the Sun, that its Centripetal Force (or thatForce 
u by which it is drawn towards the Center) is always 
“ equal to its Force, by which it doth endeavour to re- 
“ cede from the Center; for the Force, which detains a 
“ Body in its Orbit, muft be equal to the Force by 
“ which it endeavours to recede from its Orbit, and fly 
“ off in the Tangent. This maybe clear by the Ex- 
ample of a Body turn’d round a Center by the Help 
“ of a Thread, which detains the Body in its Orbit ^ 
« .the Thread, being ftretch’d by the Motion of the Body, 
will endeavour to contrad itfelf equally towards both 
“ Ends, by which it will pull the Center as much to- 
a wards the Body, as it doth the Body towards the 
“ Center. 
“ Now this Centrifugal Force is always proportional 
“ to the Periphery, which each Body defer ibes in its 
“ diurnal Motion by the firfl Theorem of Httgemus de 
u yi Centrifuga : So that under the ./Equator, which 
* is the biggeh Circle, die Centrifugal Force wou*d be 
** greateft, and hill grow lefs as we approach the Pole 
« where it quite vanifheth, there being there no diurnal 
u Rotation. And without doubt, all Bodies having this 
a Centrifugal Force, by which they endeavour to re- 
* cede from the Center of their Motion, wou’d fly off 
« from the Earth, if they were not kept in their Orbit 
“ by their Gravity, or that Force by which they are 
prefe’d towards the Center of the Earth, which is 
« much flronger upon our Earth than the Centrifugal^ 
Force:, andbecaufe the Gravity upon the Surface of 
the Earth is always the fame; but the Centrifugal 
« Force alters and grows iefs, the nearer we come to 
<« the Pole?, it is plain that the Gravity under the iE- 
“■ quator, having a greater Force to oppofc it, than that 
whicb 
