Chap. 3. PHILOSOPHY. 1 99

circuit it makes round the earth. This inequality of the moon’smotion about the earth is called by aftronomers its variation.

1 6 . The next effect of the fun upon the moon is, that itgives the orbit of the moon in the quarters a greater de-gree of curvature, than it would receive from the action ofthe earth alone ; and on the contrary in the conjunction andopposition the orbit is lefs infleCted.

17. When the moon is in conjunction with the fun inthe point D, the fun attracting the moon more forcibly thanit does the earth, the moon by that means is impelled lets to-ward the earth, than otherwife it would be, and fo the orbitis lefs incurvated ; for the power, by which the moon is im-pelled toward the earth, being that, by which it is infleCtedfrom a rectilinear courfe, the lefs that power is, the lefs itwill be infleCted. Again, when the moon is in the oppofl-tion in B, farther removed from the fun tharf the earth is;it follows then, though the earth and moon are both conti-nually defcending to the fun, that is, are drawn by the funtoward it felf out of the place they would otherwife moveinto, yet the moon defeends with lefs velocity than theearth ; infomuch that the moon in any given fpace oftime from its palling the point of oppofition will havelefs approached the earth, than otherwife it would havedone, that is, its orbit in refpeCt of the earth will ap-proach nearer to a ftraight line. In the laft place, whenthe moon is in the quarter in F, and equally diftantfrom the fun as the earth, we obferved before, that

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