f 
I ml 
about the common center of Gravity, Curve Lines, like to 
thofe they feem to defcribe about one another. And of 
three Bodies, attrading each other, reciprocally as the 
Square of the diftance between their Centers, the various 
Conftquences are confidered and laid down, in feveral Co- 
rottarys of great ufe in explicating th^ Phenomem of the 
Moons Motions, the Flux and Reflux of the Sea,, the Pre- 
ceflion of the Equinoctial Points; and the like. 
This done our Author with his ufual Acutenefs pro- 
ceeds to examine into the Caufes of this Tendency or cen- 
tripetal Force, which from undoubted- Arguments is 
Ihown to be in all the great Bodies of the Univerfe. Here 
he finds that if a Sphere be compofed of an infinity of A- 
toms, each of which have a Conatus accedendi ad invicenty 
which decreafes in duplicate Proportion of the Diftance 
between them ; then the whole Congeries ihall have the 
like tendency towards its Center, decreafing, in Spaces 
-vyithoutit, in duplicate Proportion of the Diftances from 
the Center; and decreafing, within its Surface, as the di- 
ftance from the Center direftly; fb as to be greateft on 
the Surface, and nothing at the Center: and tho' this 
might fuffice, yet to compleat the Argument, there is laid 
down a Method to determine the forces of Globes compo- 
led of Particles whole Tendencies to each other do de- 
creafe in any other Ratio of the Diftances ; Which Specu- 
lation is carryed on likewife to other Bodies not Spherical, 
whether finite or indeterminate. Laftly is propofed a 
Method of explaining the Refradions and Refleftions of 
tranfparent Bodies from the fame Principles; and feveral 
Problems (bived of the greateft Concern in the Art of D^V 
ojftricks. 
Hitherto our Author has confidered the EfFeQis of corn-* 
pound Motions //^ Mediis non refifientihus^ or wherein a 
Body once in Motion would move equably in a dired Line, 
if not diverted by a fupervening Attraftion or tendency 
toward . fome other Body. Here is demoaftrated what. 
would 
