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. Thus Air included in a vessel, by
being heated will burst it to pieces. Thus have I broke a Bladder held over
the fire in my hand, with such a violence and noise, that it almost made me
deaf for the present, and much surpassed the noise of a Musket: The like
have I done by throwing into the fire small glass Bubbles hermetically
sealed, with a little drop of Water included in them. Thus Water also, or