which pass by the edges of dense Bodies, at some distance from the
Bodies?
_Qu._ 21. Is not this Medium much rarer within the dense Bodies of the
Sun, Stars, Planets and Comets, than in the empty celestial Spaces
between them? And in passing from them to great distances, doth it not
grow denser and denser perpetually, and thereby cause the gravity of
those great Bodies towards one another, and of their parts towards the
Bodies; every Body endeavouring to go from the denser parts of the
Medium towards the rarer? For if this Medium be rarer within the Sun's
Body than at its Surface, and rarer there than at the hundredth part of
an Inch from its Body, and rarer there than at the fiftieth part of an
Inch from its Body, and rarer there than at the Orb of _Saturn_; I see
no reason why the Increase of density should stop any where, and not
rather be continued through all distances from the Sun to _Saturn_, and
beyond. And though this Increase of density may at great distances be
exceeding slow, yet if the elastick force of this Medium be exceeding
great, it may suffice to impel Bodies from the denser parts of the
Medium towards the rarer, with all that power which we call Gravity. And
that the elastick force of this Medium is exceeding great, may be
gather'd from the swiftness of its Vibrations. Sounds move about 1140
_English_ Feet in a second Minute of Time, and in seven or eight Minutes
of Time they move about one hundred _English_ Miles. Light moves from
the Sun to us in about seven or eight Minutes of Time, which distance is
about 70,000,000 _English_ Miles, supposing the horizontal Parallax of
the Sun to be about 12 . And the Vibrations or Pulses of this Medium,
that they may cause the alternate Fits of easy Transmission and easy
Reflexion, must be swifter than Light, and by consequence above 700,000
times swifter than Sounds. And therefore the elastick force of this
Medium, in proportion to its density, must be above 700000 x 700000
(that is, above 490,000,000,000) times greater than the elastick force
of the Air is in proportion to its density. For the Velocities of the
Pulses of elastick Mediums are in a subduplicate _Ratio_ of the
Elasticities and the Rarities of the Mediums taken together.
As Attraction is stronger in small Magnets than in great ones in
proportion to their Bulk, and Gravity is greater in the Surfaces of
small Planets than in those of great ones in proportion to their bulk,
and small Bodies are agitated much more by electric attraction than
great ones; so the smallness of the Rays of Light may contribute very
200