370. The Tnwerfe. Method 
_ If proper ‘data could have-been procured, an 
_attempt to calculate the motion of the Moon’s 
-Opfides would have been made. ' But finding: that 
a very {mall variation in the requifites already 
known affects the conclufions confiderably, it 
was thought beft to proceed no farther at prefent 
in fo very complicated an enquiry. 
ee 
\ 
THE INVERSE METHOD OF CENTRAL 
FORCES. 
PROPOSITION I. 
HE centripetal force being inverfely as the 
nth. power of the diftance from the 
centre, and the direction and velocity of a body 
at ‘any point v being-given ; to determine the 
‘orbit, &c.— ; 
_ Fig. I. Let C be the centre of force, V the 
point from which the body is proje@ed, V n WV 
the trajeCtory. in which it moves, and V Z 
a circle defcribed from the centre C at the dif- 
tance CV: tothe points V, », of the orbit draw 
the tangents V P, » p; and from the centre of 
‘force C let fall the perpendiculars C P, C p upon 
the tangents; join C,, and produce Cz to Y, 
and draw Cr X indefinitely near to Cy; laftly, 
draw tv perpendicular to Cm. - Put CV==r, 
Cis 
