stick together,
unless by melting them, or wetting them with Water, which by exhaling
may bring them together; and that two polish'd Marbles, which by
immediate Contact stick together, are difficultly brought so close
together as to stick.

And thus Nature will be very conformable to her self and very simple,
performing all the great Motions of the heavenly Bodies by the
Attraction of Gravity which intercedes those Bodies, and almost all the
small ones of their Particles by some other attractive and repelling
Powers which intercede the Particles. The _Vis inertiae_ is a passive
Principle by which Bodies persist in their Motion or Rest, receive
Motion in proportion to the Force impressing it, and resist as much as
they are resisted. By this Principle alone there never could have been
any Motion in the World. Some other Principle was necessary for putting
Bodies into Motion; and now they are in Motion, some other Principle is
necessary for conserving the Motion. For from the various Composition of
two Motions, 'tis very certain that there is not always the same
quantity of Motion in the World. For if two Globes joined by a slender
Rod, revolve about their common Center of Gravity with an uniform
Motion, while that Center moves on uniformly in a right Line drawn in
the Plane of their circular Motion; the Sum of the Motions of the two
Globes, as often as the Globes are in the right Line described by their
common Center of Gravity, will be bigger than the Sum of their Motions,
when they are in a Line perpendicular to that right Line. By this
Instance it appears that Motion may be got or lost. But by reason of the
Tenacity of Fluids, and Attrition of their Parts, and the Weakness of
Elasticity in Solids, Motion is much more apt to be lost than got, and
is always upon the Decay. For Bodies which are either absolutely hard,
or so soft as to be void of Elasticity, will not rebound from one
another. Impenetrability makes them only stop. If two equal Bodies meet
directly _in vacuo_, they will by the Laws of Motion stop where they
meet, and lose all their Motion, and remain in rest, unless they be
elastick, and receive new Motion from their Spring. If they have so much
Elasticity as suffices to make them re-bound with a quarter, or half, or
three quarters of the Force with which they come together, they will
lose three quarters, or half, or a quarter of their Motion. And this may
be try'd, by letting two equal Pendulums fall agains