25 8. Mathematical Elements Book IV.

1330 Motions- before explain’d ; but there is a Forcewhich removes the Moon from the Plane of the Or-

*1314 hit*, so that we must conceive that Plane to beagitated, otherwise the Moon would go out ofthe Orbjt.

133 1 Plate XXV. Fig. 1.] Let the Moon be at F 5is we attend to what has been said above concern-

* ,2 99 ing the Actions of the Sun*', it is plain that thePlane of the Parallelogram F H M I goes thro'the Line T 8, which joins the Centers of theEarth and Sun, and therefore it is in the Plan?of the Ecliptic ; so that the Point N, to which 1Sdirected the Force F N, disturbing on accountof the Action of the Sun, is in that Plane.

1332 Plate XXV. Fig, 4.] Let the fame Force be' represented by pi; at F let F R be rais’d perpen-dicular to the Plane of the Orbit, and imagin?the Parallelogram,FR If,, whose Side F i is ‘ nthe Plane of the Orbit, and whose Diagonal isF I, the disturbing Force along FI is refolv’d in-

* 192 tQ two the Directions, F R and Fr, which theseLines represent*, .and of which this last acts in thePlane of the Qrbit; so that we must refer to thiswhat relates to the disturbing Force, of which V s ?have treated in N Q -1299 ; , for the Lines F i- andF I scarce differ,. and. the Plane of the Parallelo-gram F RI [i is perpendicular to the r Plane -of theMoon’s Orbip

1333 The Line F R must be,deterfnin’d, which re 'presents, the Force thapacts perpendicular ty thePlane qf; the Orbit, and removes theMoon stoso

thatiPlane ;.no^ the-rela-pon of the Linc-F R of

Ipto the Radim.ET, is the Ratio of the distur-bing force which is spoken: of-here, tophelncr^f^'

*1286 of Orayitydn the.Qua.drafure?*.