wherein the thicknesses of colour'd Plates of Water between two Glasses
are set down, the thickness of the Plate where it appears very black, is
three eighths of the ten hundred thousandth part of an Inch. And where
the Oil of Oranges between the Glasses is of this thickness, the
Attraction collected by the foregoing Rule, seems to be so strong, as
within a Circle of an Inch in diameter, to suffice to hold up a Weight
equal to that of a Cylinder of Water of an Inch in diameter, and two or
three Furlongs in length. And where it is of a less thickness the
Attraction may be proportionally greater, and continue to increase,
until the thickness do not exceed that of a single Particle of the Oil.
There are therefore Agents in Nature able to make the Particles of
Bodies stick together by very strong Attractions. And it is the Business
of experimental Philosophy to find them out.
Now the smallest Particles of Matter may cohere by the strongest
Attractions, and compose bigger Particles of weaker Virtue; and many of
these may cohere and compose bigger Particles whose Virtue is still
weaker, and so on for divers Successions, until the Progression end in
the biggest Particles on which the Operations in Chymistry, and the
Colours of natural Bodies depend, and which by cohering compose Bodies
of a sensible Magnitude. If the Body is compact, and bends or yields
inward to Pression without any sliding of its Parts, it is hard and
elastick, returning to its Figure with a Force rising from the mutual
Attraction of its Parts. If the Parts slide upon one another, the Body
is malleable or soft. If they slip easily, and are of a fit Size to be
agitated by Heat, and the Heat is big enough to keep them in Agitation,
the Body is fluid; and if it be apt to stick to things, it is humid; and
the Drops of every fluid affect a round Figure by the mutual Attraction
of their Parts, as the Globe of the Earth and Sea affects a round Figure
by the mutual Attraction of its Parts by Gravity.
Since Metals dissolved in Acids attract but a small quantity of the
Acid, their attractive Force can reach but to a small distance from
them. And as in Algebra, where affirmative Quantities vanish and cease,
there negative ones begin; so in Mechanicks, where Attraction ceases,
there a repulsive Virtue ought to succeed. And that there is such a
Virtue, seems to follow from the Reflexions and Inflexions of the Rays
of Light. For the Rays are repelled by Bodies in both these Cases,
without the immediate Contact of the reflecting or inflecting Body. It
seems also to follow from the Emission of Light; the Ray so soon as it
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