Of Fire-workes.
I haue euer found (in conference with diuers desirous of instruction in any Art or Science whatsoeuer) that the summe and chiefest end of all hath been, to know the reasons and causes of those things they were desirous to be informed in. Wherefore I thought good, before I came to the matter it selfe, to set down some few Præcognita or Principles (as I may so call them) whereby such as are ingenious, upon occasion, may informe themselues, if they stand in doubt of the cause of any thing that is heereafter taught.
Certayne Præcognita or Principles wherein are contayned the causes and reasons of that which is taught in this Booke.
1 The foure Elements, Fire, Ayre, Earth, and Water, are the prima principia (I meane the materialls) whereof euery sublunary body is composed, and into the which it is at last dissolued.
2 Euery thing finding a dissolution of those naturæ catenæ, that is, meanes whereby their principia are connected, and ioyned together, their lighter parts ascend upward, and these that are more grosse and heauy, doe the contrary.
3 It is impossible for one and the selfe same body to possesse at one time two places; It followeth therefore, that a dense body rarified, and made thin, eyther by actuall or potentiall fire, requireth a greater quantity of room to be conteyned in, then it did before. Hence it is, that if you lay your hand upon a glasse, hauing a straight mouth reuerst into a dish of water, it rarifieth the ayre contayned therein, and makes it breake out thorough the water in bubbles. Also, that gunpowder inclosed in the barrell of a gun, being rarified by fire, applied unto the touch-hole, it seeketh a greater quantity of roome, and therefore forceth the bullet out of the barrell. This is called violent motion.
4 According unto the strength and quantity of a dense body rarified, and according unto the forme and length of its inclosure, it forceth its compresser further or neerer at hand.