Full text: Bacon, Francis: Sylva sylvarum

Century I. and ſprinkle up in a fine Dew. This inſtance doth excellently demonſtrate
the force of Compreßion in a ſolid Body. For whenſoever a folid Body (as
Wood, Stone, Metal, & c.) is preſſed, there is an in ward tumult in the parts
thereof, ſeeking to deliver themſelves from the Compreſſion: And this is
the cauſe of all Violent Motion. Wherein it is ſtrange in the higheſt degree,
that this Motion hath never been obſerved, nor enquired; it being of all
Motions, the moſt common, and the chief root of all Mechanical Operations. This Motion worketh in round at firſt, by way of Proof and Search, which
way to deliver it ſelf, and then worketh in Progreſs, where it findeth the
deliverance eaſieſt. In Liquors this Motion is viſible; for all Liquors ſtruck-
en, make round circles, and withal daſh, but in Solids (which break not) it is
ſo ſubtile, as it is inviſible; but nevertheleſs bewrayeth it ſelf by many
effects, as in this inſtance whereof we ſpeak. For the Preſſure of the Finger
furthered by the wetting (becauſe it ſticketh ſo much the better unto the
Lip of the Glaſs) after ſome continuance, putteth all the ſmall parts of the
Glaſs into work, that they ſtrike the Water ſharply; from which Percußion,
that ſprinkling cometh.



If you ſtrike or pierce a Solid Body that is brittle, as Glaſs or Sugar, it
breaketh not onely where the immediate force is, but breaketh all about
into ſhivers and fitters; the Motion upon the Preſſure ſearching all ways,
and breaking where it findeth the Body weakeſt.



The Powder in Shot being dilated into ſuch a Flame, as endureth not
Compreſſion, moveth likewiſe in round (the Flame being in the nature of
a Liquid Body) ſometimes recoyling, ſometimes breaking the Peece, but
generally diſcharging the Bullet, becauſe there it findeth eaſieſt deliver-



This Motion upon Preſſure, and the Reciprocal thereof, which is Mo-
tion upon Tenſure; we uſe to call (by one common name) Motion of Liber-
ty; which is, when any Body being forced to a Preternatural Extent or Di-
menſion, delivereth and reſtoreth it ſelf to the natural: As when a blown
Bladder (preſſed) riſeth again; or when Leather or Cloth tentured, ſpring
back. Theſe two Motions (of which there be infinite inſtances) we ſhall
handle in due place.



This Motion upon Preſſure is excellently alſo demonſtrated in Sounds: As when one chimeth upon a Bell, it ſoundeth; but as ſoon as he layeth his
hand upon it, the Sonnd ceaſeth: And ſo, the ſound of a Virginal String, as
ſoon as the Quill of the Jack falleth from it, ſtoppeth. For theſe ſounds are
produced by the ſubtile Percuſſion of the Minute parts of the Bell or String
upon the Air; All one, as the Water is cauſed to leap by the ſubtile Percuſſi-
on of the Minute parts of the Glaſs upon the Water, whereof we ſpake a lit-
tle before in the Ninth Experiment. For you muſt not take it to be the local
ſhaking of the Bell or String that doth it. As we ſhall fully declare when
we come hereafter to handle Sounds [?] .



TAke a Glaß with a Belly, and a long Neb, fill the Belly (in part) with
Water: Take alſo another Glaß, whereinto put Claret Wïne and Water
mingled. Reverſe the firſt Glaſs, with the Belly upwards, ſtopping the
Neb with your Finger; then dip the mouth of it within the ſecond Glaſs,
and remove your Finger. Continue it in that poſture for a time, and it
will unmingle the Wine from the Water; the Wine aſcending and ſetling in
the top of the upper Glaſs, and the Water deſcending and ſetling in the
bottom of the lower Glaſs. The paſſage is apparent to the Eye; for


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