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lows that Kepler’s third law is only another
way of saying that the sun’s force on differ-
ent planets (besides depending as above on
distance) is proportional to their masses.
Having further proved the, for that day,
wonderful proposition that, with the law of
inverse squares, the attraction by the sep-
arate particles of a sphere of uniform den-
sity (or one composed of concentric spheri-
251