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It will be found, in like manner, that the moment 
of the point g‘ to turn about the centre C, is S x SC x 
or with regard to the 
point I which is on the oppofite fide of the centre to 
the point /, this moment, by changing the figns, 
will be, Sx SCxf =7 — =JL- )xg' x C I = S x SCx 
V SC S g' y 
r ==r- 3 — ~r~ i ) x o- x C I. Therefore the moment 
sc s g y ° 
of the two equal points g and g to caufe the point 1 
to turn about the centre 6', is S x S C x f ==7 — ==7 ) 
[ Sg sc } y 
xgxCl + SxSCxf JL Jx s xCI = 
g x C l*SxSCx(=p — = 
If the points y and y be taken equally diftant from 
the points D and D\ as the points g and g\ it will 
likewife be found, that the moment of the equal 
points y and y to caufe the point I to turn about the 
centre C, is y x C 1 x S x S C x f -^-3 J y x 
C 1 * Sx SCx f ==5 — =jFTi )• 
{ sg sg y 
Therefore the moment of all the four points to- 
gether, g , g y y, y y to caufe the point I to tui n about 
the centre C> is(£ — y) *C1* S x S C x ^ =p —7 ), 
which 
