This Conjecture of mine I shall indeavour to make out by explaining each
particular Assertion with _analogous_ Experiments: The Assertions are
there.
First, That the parts of the Glass, whilst in a fluid Consistence and
hot, are more rarified, or take up more room, then when hard and cold.
Secondly, That the parts of the drop do suffer a twofold contraction.
Thirdly, That the dropping or quenching the glowing metal in the Water
makes it of a hard, springing, and rarified texture.
Fourthly, That there is a flexion or force remaining upon the parts of
the Glass thus quenched, from which they indeavour to extricate
themselves.
Fifthly, That the Fabrick of the drop, that is able to hinder the parts
from extricating themselves, is _analogus_ to that of an Arch.
Sixthly, That the sudden flying asunder of the parts proceeds from
their springiness.
Seventhly, That a gradual heating and cooling does anneal or reduce the
parts of Glass to a texture that is more loose, and easilier to be
broken, but not so brittle.
That the first of these is true may be gathered from this, That _Heat is a
property of a body arising from the motion or agitation of its parts_; and
therefore whatever body is thereby toucht must necessarily receive some
part of that motion, whereby its parts will be shaken and agitated, and so
by degrees free and extricate themselves from one another, and each part so
moved does by that motion _exert_ a _conatus_ of _protruding_ and
displacing all the adjacent Particles.
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