OF THE ECLIPSES OF THE

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by the nodes but twice a year, and the moon’sorbit contains 360 degrees, of which seventeen,the limit of solar eclipses, on either side of thosepoints, and twelve the limit of lunar eclipses,are but small portions, it is easy to perceive thatthere must be many new and full moons withoutany eclipses.

The limits I have mentioned are subject tosome variations; but, as a scrupulous accuracy,in a popular explanation of this kind, would betedious and unnecessary, I siiall proceed to illus-trate the general doctrine by a figure. For thispi. xvii. purpose, let A B C D be the ecliptic, or theearth’s path in the heavens; RSTU a circlelying in the same plane, and V WX Y the moon’sorbit; one half of which X Y Y is above theecliptic, and the other half V W X below it.Then will the points V and X, where the twocircles intersect each other, be the moon’s nodes;and the right line X E Y, drawn from the oneto the other, through the earth’s center, will bethe line of the nodes ; which is carried in a po-sition, nearly parallel to itself, round the sun ina year.

Now it is plain from the figure, that if themoon moved round the earth in the circleR S T U, which is coincident with the plane ofthe ecliptic, her Ihadow would fall upon theearth every time she was in conjunction withthe fun ; and at every opposition sire would go

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