pieces; for all the Springs of the several parts are set at liberty, which immediately extricate themselves and fly asunder every way; each part by its spring contributing to the darting of it self and some other contiguous part. But if this drop be heat so hot as that the parts by degrees can unbend themselves, and be settled and annealed in that posture, and be then suffered gently to subside and cool; The parts by this nealing losing their springiness, constitute a drop of a more soft but less brittle texture, and the parts being not at all under a flexure, though any part of the middle or Pith T E E E be broken, yet will not the drop at all fly to pieces as before.
This Conjecture of mine I shall indeavour to make out by explaining each particular Assertion with analogous Experiments: The Assertions are these.
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. 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 any other Liquor, included in a convenient vessel, by being warmed, manifestly expands it self with a very great violence, so as to break the strongest vessel, if when heated it be narrowly imprisoned in it.
