Page:Cyclopaedia, Chambers - Volume 1.djvu/555

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Since then the Experiments ofRiccioluS, made in fuch confiderable Difhmces, agree lb well to the Theory, 'tis

fcarce worth taking Notice of what is urged to the contra- ry by 2)echa/es, in his Mund. Math, who writes, that he had found by Experiment, that heavy Bodies in halfa Se- cond of Time dejeend 4^ Eeet ; in two i6~ ; in three 3^5 in four 601 in five 90 ; in fix 123. Tis fufficient, that he deduces the Irregularity from th^ Refinance of the Air, which we fuppofe out of theQueftion.

II If a heavy Body defcend in an unrefiftine Medium through an Interval not over-large, the Space it defcribes is fitbduple of that which it would defcribe in the fame Time with the Velocity acquired at the End of the FalU

HI. The Time wherein a Body falls from a given Height being given, to determine the Spaces it fell in thefe- vera"! Parts of that Time.

Suppofe the given Altitude —a the Time =t and the Space it fell in r Part of Time x : Then 1 : x — t z :z

x=a:t*

Therefore the Space pafs'd over in the firft Part of Time is a: t ' ; Confequently that pafs'd over in the fecond Time era*:* =, That in the third — 5 3 :t I &c.

jE.gr. In the Experiments of Ricciolus above dcliver'd; the Ball fell 240 Feet in 4 Seconds. Therefore the Space fell the firft fecond was —240 : i6"=:i 5. The Space in the fecond was ==15.3 —45- That in the third— 15.5 —75. And that in the fourth 15.7— 105.

IV. The Time wherein a Body falls a given Space, being given ; to determine the Time wherein it wiJl fall any other given Space in the fame Medium.

Since the Spaces are as the Squares of the Times : To the Space which the Body falls in the given Time, the Space in the Queftion, and the Square of the given Time find a fourth Proportional, which will be the Square of the Time fought. The Square-Root, therefore, being extracted there- from, the Problem is folved.

For Example, one of Ricciolus^ Balls in 4 Minutes Time falling 240 Foot, it is required in what Time it would fall 135 Foot ? The Anfwer will be foundry (135: 15:240.) ^(135:15) = Y 9=3.

V. TheSpace a Body falls in a given Time, being given, to determine the Space it will fall in any other given Time.

To the Square of theTime wherein theBody falls the given Space, the Square of the Time wherein it Jhould fall the Space required, and the given Space, feek a fourth Propor- tional 5 This will be the Space required.

For Inftance, Ricciolus's Ball falling 60 Foot in 2 Se- conds, 'tis aih'd what Space it will fall in 4 Seconds ? The Anfwer is, 16.60: ^.=.^.60=. 240.

For the Laws of the Defcent of Bodies on inclined ^Planes. See Inclined 'Ptaita*

For the Laws of Defcent in Cycloids, See Cycloid, and Pendulum.

Line of quickeft Descent, is that which a Body falling by the Aclion of Gravity defcribes in the fliorteft Time 5 ■which is prov'd by Geometricians to be the Cycloid. See Cycloid, and alfo Celerrimi 2)efcenfm Linea.

Descents, in Fortification, fignify the Holes, Vaults, and hollow Places, made by undermining the Ground: fuch as the Counter-fcarps, or Covert-way.

A 'Defcent into the Moat, or Ditch, is a deep digging into the Earth of the Covert-way, in Form of a Trench; of which the upper Part is cover'd with Madriers, or Clays againft Fires, to fecure the ParTage into the Moat.

DESCB.1BENT, is aTerm inGeometry, expreffing fome Line, or Surface, which by its Motion produces a Plane Figure, or a Solid.

DESCRIPTION, a fuperficial, imperfecl, orunaccurate Definition of a Thing; giving a Sort of Knowledge thereof from fome Accidents, and Circumflances peculiar toit, which determine it enough to give an Idea that may diftinguifh it from other Things ; but without explaining its Nature, or EfTence.

Grammarians content themfelves with liefcriftions: but Philofophers require exact. Definitions of Things. See De- finition.

Description, in Philofophy, Logic, &c. is anEnume- ration of divers Attributes of a Thing, molt, of which are only accidental : As when. a Perfon is defcribed by his Deeds, "is Sayings, his Writings, his Honours, ££&, Sec Defini- tion.

A Defer iption, as to its outward Appearance, refembles ^Definition ; and is even convertible with the Thing de- fcribed ■ but does not explain it. For inftead of bringing ieveralThings effentiai to theThing defcribed, it only brings a Number of Accidents belonging thereto. E.gr. Peter is the tali, young Man who lives on the Green, wears black Clothes, frequents theColtege, Courts Is. . . .  but to that, jgro's eft ? Who is he P.

Ttefcripioni, in Effect, are principally ufed for Singu- lars, or Individuals : For Things of the fame Species .do not differ in Effencc, but only as toHic, and Hie, which Difference contains nothing very notable, or diftinguifhable. But Individuals of the fameKind, differ much in Accidents - E. gr. George is King, and William a Citizen ; Charles is a Male, and Anne a Female 5 Henry is wife, and John a Blockhead, &c. Thus, a Uefcription is an Accumulation of Accidents, whereby Things are notably diftinguifh'd from each other, tho' they fcarcc differ at all inEffence.

Some Authors call aTJefcription a^a/J-Definition 5 As Body is a Thing divifible, moveable, [olid, extended, &c. only wanting of a Definition in this, that inftead of the Form, or Effencc of a Thing, it gives one, or more Pro- perties arifing from the Form, or Effence. See Defi- nition, Essence, Form, iSc.

Description, inRhetoric. See Definition. Description, inGeometry. To defcribe a Circle, El- lipfis, Parabola, SSc. is to conllruct, or form thofe Figures, with Rules, Compaffes, Sc. See Construction, and Figure.

DESERT, orDESART, aWildernefs; or wild, uncul- tivated, uninhabited Place : As the Deferts of Lybia, of the Thebaide.

Geographers ufe the Word in the general for all Countries little, or not at all inhabited. See Wilderness,

In Scripture, we find feveral Places in the Holy Land, or Places adjoyning thereto, call'd Uefarts. The Xtefart, or Wildernefs, fimply, is that Part of Ara bia on the South of the Holy Land, wherein the Jfraelites wandred forty Years, from the Time of their Evacuating Egypt to their Entry into the promis'd Land. The tDefart ofSerfabea was that Part of the ZJefart juit mention'd, which border'd on the Holy Land, running towards the Mediterranean. The Tie- fart of Idumea, is Idumea it felf, a barren, mountainous Country. The Defarts of Setharen, Sethfaide, Cadefh, 'Damafcus, T)ibla, Engaddi, Ethom, Gibeon, Horeb, Jer- nel, Juda, Moab, Tharan, Sin, Sinai, Sur, Ziph, &c. are fo many dry, uncultivated, and frequently mountainous Places, like our Downs, £5 c. where there are few, or no Habitations, or Inhabitants ; whence the Hebrews call'd them by Autiphrafis na*Ja> which properly fignifies hu- man Word-, or Speech, by reafon there was none heard there.

DESERTER, in War, a Soldier on the Mufter-roli; who quits his Cqmpany without Leave; or lifts himfclf un- der another Officer.

All Soldiers found halfa League from a Garrifon, or Ar- ™y> g° in g towards an Enemies Country, or Quarters, with- out a Pais, are deem'd, and treated as Dej'erters.

The Punilhment of X)eJertion, is Death.

The ancient Church excommunicated Deferters, as ha- ving violated their Oath.

DESHABILLE, a French Term, naturalized of late. It properly fignifies a Toilette, Night-Gown, and other Ne- ceffaries, made ufe of in drefling, or undreffing. Mr. is not to be fpoke withal j he is yet in his Dejhabille, i.ei undrefs'd, or in his Night-Gown.

The Word is a Compound of the Privative de, and s'ba- biller, to drefs.

DESHACHEE, in Heraldry, is when a Beaft has its Limbs feparated from the Body, fo as they ftill remain on the Efcutcheon, with only a fmall Separation from their na- tural Places.

DESIGN, or Draught, with regard to the Arts and Sciences, fignifies the Thought, Plan, Geometrical Repre- fentation, Diftribution, and Conftruftion of a Paintino, Poem Book, or Building.

This Painter has lhewn the firft Tiefign of his Piece, in which the Figures are well difpofed. The 2)eflgti of that Poem or Book is artfully laid.

Claudian never fees his whole Defign together : When he compofes a Part, he thinks of nothing elfej and works up every Member, as if it were fsparate from all the reft.

In Building, one may ufe the Term Ichnograpby, when by Tlefign is only meant the Plan of a Building, or a flat Figure drawn onPaper. See Ichnography.

Orthography, when fome Face, or Side of the Building is rais'd from the Ground. See Orthography.

And Scenography, when both Front and Sides are feen in Perfpeftive. See Scenography.

Design, in theManufaftories, the Figures wherewith the Workman enriches his Stuff, or Silk ; and which he copies after fome Painter.

In undertaking fuch Kinds of figured Stuffs,- 'tis heceffa- ry, that before the firft Stroak of the Shuttle, the whole ffle- fign be reprcfented on the Threads ol the Warp ; we don't