Book IV. of Natural Philosophy. 261

Whilst the Earth is carried round the Sun (evenWhen we do not attend to the above-mention’dMotion of the Nodes) the Line of Nodes A oes suc- 1343cessively acquire all possible Situations in respectof the Sun, and every Tear goes twice thro ’ the Sy-zygies, and twice thro ’ the Quadratures.

If now we consider several Revolutions of the Moon , 1344the Nodes in one whole Revolution go back very fast,the Nodes being in the Quadratures* ; then sower, * 1339till they come to rest, when the Line of Nodes is in theSyzygies*. *1338

By the same Force with which the Nodes are 1345mov’d, the Inclination of the Orbit is also chang’d ;it is increased as the Moon recedes from the Node, anddiminish'd as it comes to the Node.

Plate XXV. Fig., 6.] For the Angle bp L is less j 346than the Angle A P L, and for the fume Cause itis continually diminifli’d, and the Inclination be-comes greater; but when the Moon is come tothe greatest distance from the Plane of the Eclip-tic, and is going towards the opposite Node, theDirection of the Moon is continually inflected to-wards the Plane of the Ecliptic, and less inclin’dto it than if it continu’d in motion in its Orbit;let N pn be the Plane of the Ecliptic, the CurveN n the Orbit of the Moon, by the force wherebythe Moon is continually remov’d out of it, theWay of the Moon is chang’d, and it goes in theCurve N p, which is more inclin’d to N pn at Nthan at p-, so that we must conceive the Inclina-tion of the Plane of the Orbit to be twice chan-ged * whilst the Moon moves from one Node to *1^4the other, therefore this happens four times; ine ach Revolution of the Moon it is twice diminish'd, 1347and twice again increased.

Plate XXV. Fig. 4.] Supposing the Nodes N n 1348to be in the Quadratures, the Forces which in oneRevolution increase the Inclination and diminish it

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