t one another from
equal heights. If the Pendulums be of Lead or soft Clay, they will lose
all or almost all their Motions: If of elastick Bodies they will lose
all but what they recover from their Elasticity. If it be said, that
they can lose no Motion but what they communicate to other Bodies, the
consequence is, that _in vacuo_ they can lose no Motion, but when they
meet they must go on and penetrate one another's Dimensions. If three
equal round Vessels be filled, the one with Water, the other with Oil,
the third with molten Pitch, and the Liquors be stirred about alike to
give them a vortical Motion; the Pitch by its Tenacity will lose its
Motion quickly, the Oil being less tenacious will keep it longer, and
the Water being less tenacious will keep it longest, but yet will lose
it in a short time. Whence it is easy to understand, that if many
contiguous Vortices of molten Pitch were each of them as large as those
which some suppose to revolve about the Sun and fix'd Stars, yet these
and all their Parts would, by their Tenacity and Stiffness, communicate
their Motion to one another till they all rested among themselves.
Vortices of Oil or Water, or some fluider Matter, might continue longer
in Motion; but unless the Matter were void of all Tenacity and Attrition
of Parts, and Communication of Motion, (which is not to be supposed,)
the Motion would constantly decay. Seeing therefore the variety of
Motion which we find in the World is always decreasing, there is a
necessity of conserving and recruiting it by active Principles, such as
are the cause of Gravity, by which Planets and Comets keep their Motions
in their Orbs, and Bodies acquire great Motion in falling; and the cause
of Fermentation, by which the Heart and Blood of Animals are kept in
perpetual Motion and Heat; the inward Parts of the Earth are constantly
warm'd, and in some places grow very hot; Bodies burn and shine,
Mountains take fire, the Caverns of the Earth are blown up, and the Sun
continues violently hot and lucid, and warms all things by his Light.
For we meet with very little Motion in the World, besides what is owing
to these active Principles. And if it were not for these Principles, the
Bodies of the Earth, Planets, Comets, Sun, and all things in them,
would grow cold and freeze, and become inactive Masses; and all
Putrefaction, Generation, Vegetation and Life would cease, and the
Planets and Comets would not remain in their Orbs.

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