tET. VII. AND DISCOVERIES. IIZ

in itself, but it admits of the most rigorous de-monstration. Newton, by means of his geo-metry, has ascertained this gradual diminutionof weight, and calculated its precise propor-tion ; which, at all distances below the surfaceof the earth, he found to be proportional to thedistance from the center.

Having thus examined the internal recesses ofthe earth, let us now extend our researches tothe heavens ; and we shall have equal reason toconclude, that a certain diminution of gravity,must likewise follow at different heights abovethe earth’s surface. For since this power actsin straight lines, which constantly diverge, orbecome wider apart, the further they are pro-duced from the center, it is plain that theaction of gravity must be weaker upon the samebody at a greater distance than at a smaller, onaccount of the power being more diffused.This, however, is only a popular illustration; butthe truth of it has been fully confirmed by New-ton, who has demonstrated that the gravity ofbodies, above the earth’s surface, continually di-minishes as the squares of their distances fromthe center increase: or, which is the same thing,that the forces are as 4 to 1, when the distancesfrom the center are as 1 to 2; as 9 to 1, whenthe distances are as 1. to z; and so on.

from this account, you will readily perceivethat gravity is a certain force, which acts upon

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