lly pervious
every way. And, according as these pores are more or greater in respect of
the _interstitial_ bodies, the more transparent are the so constituted
concretes; and the smaller those pores are, the weaker is the _Impulse_ of
light communicated through them, though the more quick be the progress.

Upon this Occasion, I hope it will not be altogether unseasonable, if I
propound my conjectures and _Hypothesis_ about the _medium_ and conveyance
of light.

I suppose then, that the greatest part of the _Interstitia_ of the world,
that lies between the bodies of the Sun and Starrs, and the Planets, and
the Earth, to be an exceeding fluid body, very apt and ready to be mov'd,
and to communicate the motion of any one part to any other part, though
never so far distant: Nor do I much concern my self, to determine what the
Figure of the particles of this exceedingly subtile fluid _medium_ must be,
nor whether it have any interstitiated pores or vacuities, it being
sufficient to solve all the _Phaenomena_ to suppose it an exceedingly
fluid, or the most fluid body in the world, and as yet impossible to
determine the other difficulties.

That being so exceeding fluid a body, it easily gives passage to all other
bodies to move to and fro in it.

That it neither receives from any of its parts, or from other bodies; nor
communicates to any of its parts, or to any other body, any impulse, or
motion in a direct line, that is not of a determinate quickness. And that
when the motion is of such determinate swiftness, it both receives, and
communicates, or propagates an impulse or motion to any imaginable distance
in streight lines, with an unimaginable celerity and vigour.

That all kind of solid bodies consist of pretty massie particles in respect
of the particles of this fluid _medium_, which in many places do so touch
each other, that none of this fluid _medium_ interposes much after the same
mannner (to use a gross similitude) as a heap of great stones compose one
great _congeries_ or mass in the midst of the water.

That all fluid bodies which we may call _tangible_, are nothing but some
more subtile parts of those particles, that serve to constitute all
_tangible_ bodies.

That the water, and such other fluid bodies, are nothing but a _congeries_
of particles agitated or made fluid by it in the same manner as the
particles of _Salt_ are agitated or made fluid by a parcel of water, in
which they are dissolv'd, and subsid