Page:Cyclopaedia, Chambers - Volume 1.djvu/381

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From this Table, the Field is to be plotted, or protraSed ; For the Manner whereof, fee Plotting, andPROTRACTioN.

Note, Where Security is to be confulrcd rather than Dif- patch, it may be convenient to take Back-fights ; i. e. to place the Inftrument fo, at each Station, as that looking backwards thro' the Sights to the laft Station, the North Fed of the Needle may point to the fame Degree as the South End did, in looking forwards from the lait Station to this. See Theodolite, and Plain-Table: Both which Inftrumcnts arc us'd, on occafion, as Circumfercntors.

CIRCUMFLEX, in Grammar, an Accent, ferving to note, or diftinguiih a long Syllable. See Accent, Long, cS?c.

The Greeks had three Accents, the Acute, the Grave, and the Circumflex, form'd thus ', \". In EnglijJo, French, &c. the Circumflex is made thus A. See Character.

The Acute raifes the Voice, and the Grave falls, or low- ers it : the Circumflex is a kind of Undulation, or wavering of the Voice, between the two. See Acute, Grave, &c.

'Tts feldom us'd unlefs to lhew the Omiiiion of a Let- ter which made the Syllable long and open ; a thing vaftly more frequent in the French than among us : Thus they write : f*te, for pajie ; tlte, lor tefte 5 f&mes, forfufmes,lkc. They alfo ufe the Circumflex in the Participles ; fome of their Authors writing comieu, fee, others, comw, pit, ckc. Fa- ther Huffier is at a Lofs for the Reafon of the Circumflex on ibis occafion.

The Form of the Greek Circumflex was antiently the fame with that of ours : but the Copifts changing the Form of the Characters, and introducing the running Hand, chang'd alfo the Form of the Circumflex Accent; and inftead of making a juft Angle, founded it off, adding a Dafli thro' too much haft ; and thus form'd an s, inverted and laid ho- rizontally, which produe'd this Eigure ", inftead of this A.

CIRCUMLOCUTION, a Circuit, or Tour of Words, us'd either when a proper Term is not at hand, to exprefs a thing naturally and immediately by; or when one chufesnot to do it, out of refpeef ; or on fome other occafions.

The Word comes from the Latin Circumloquor, I fpeak about.

Circumlocution, in Oratory, is the avoiding of fome- thing difagreeable, or inconvenient to be exprefs s d in direft Terms ; by intimating the Senfe thereof in a kind of Para- phrafe, fo conceiv'd as to foften, or break the Force thereof.

Thus Cicero, unable to deny that Clodkls was ilain by Mile, owns it, with this Circumlocution, ' Mile's Servants ' being prevented from afiifting their Mafter, who was re- ' ported to be kill'd by Clodim ; they, in his abfence, and c would expect from their own Servants on fuch an occafion.'
 * without his Privity, or Confent, did what every body

CIRCUMINCESSION, in Theology, a Term whereby the Schoolmen ufe to exprefs the Exittence of three divine Perfoni in one another, in the Myftery of the Trinity. See Person.

The School-Divines are not the firft Authors of this Tetm ; Damafccnm, in the VHIth Century, having us'd the Wotd nie<2«f»« f > which fignifies the fame thing, in his Explanation of that Text, I am in my Father, and my Father is in me.

CIRCUM 'Polar Stars, are fuch Stars as being pretty near our North-Pole, move around it ; and in our Lati- tude, never let, or go below the Horizon. See Star, Pole, Setting, £S?c.

CIRCUMSCRIBING, in Geometry, denotes the defcri- bing a polygonous Figure about a Circle, in fuch manner, as that all its Sides are Tangents to the Circumference. See Circle, Polygon, &c.

lne Term is fometimes alfo us'd for the defcribing of a Circle about a Polygon ; fo, as that each fide is a Chord. But in this Cafe, we more ufually fay, the Polygon is in- ferred, than the Circle circumfcribed. See Inscribing.

Any^ regular Figure A B C D E, (Plate Geometry, Fig. 29.) inferib'd in a Circle, is refolv'd into equal and fimilar Trian- gles, by Radii drawn from the Centre of the circumfcribing Circle F, to the feveral Angles of the Figure ; and its Area is equal to a teftangled Triangle, whofe Bafe is equal to the Circumference of the whole Polygon ; and its Height a Per- pendicular let fall from the Centre F to one fide AB.

The fame may be faid of the Area of the circumfcribing Circle abede, excepting that the Height is to be the Ra- dius.

The Area of every Polygon that can be inferib'd in a Cir- cle is lefs; and that of every Polygon that can be circum- fcrib'd, greater than that of the Circle : In like manner, the Perimeter of the firft is lefs, and that of the fecond greater than the Circumference of the Circle. See Perimeter,^.

On this Principle Archimedes attempted the Quadrature of the Circle ; which is nothing elle, in effefl, but the mea- furmg of the Area, or Capacity of a Circle. See Quadra- ture.

The Side of a Hexagon is equal to the Radius of a cir- Cumfcnb'd Circle. Sec Hexagon.

To Circumfcribe a Circle about any given regular Polygon, ABC; (Fig. ; .) and vice verfa. Biflecr two of the An-

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gles, v.g A and B; and on the Point F, where the two Lines of Biffeftion interfea, as on a Centre, defcribe a Cir- cle with the Radius F A.

To Circumfchbe a Square about a Circle. , Draw two Di- ameters, AB and D E, (Fig. 31.) interfeaing each other in the Centre C, atright Angles. From A E B D, with the Interval of the Radius, make Interfeflions in F,G H 1 Draw the right Lines F G, G H, I H, and I F. Then is F G H I a Square circumfcrib'd about the Circle.

To circumfcribe any regular 'Polygon, v.g. a Pentagon, about a Circle. Biffeft the Chord A E, (Fig. 32.) by the Perpendicular F G, which continue till it cut the Arch in g. Thro' A and E, draw the Radii A F and E F : and thro' g draw a Line parallel to AE, meeting the Radii continu'd on each fide in a and e : Then is a e one fide of the cir- cumfcrib'd Polygon. Produce the Radius F B to b, till F b _ Fa ; and draw a b .- this is another Side of the Poly- gon ; and in the fame manner may the reft of the Sides be drawn.

To Infiribe any regular Polygon in a Circle. Divide 3U0 by the number of Sides, in order to find the Quantity of the Angle E F D ; which make at the Centre, and apply the Chord to the Periphery as often as it will go. Thus will the defir'd Figure be inferib'd in the Circle.

CIRCUMSTANCES, the Incidents of an Event, or the Particularities that accompany an Action. See Incident.

Divines fay, the Converfion of a Sinner depends on a cer- tain Aflemblage, and a certain Management of external Cir- cumflances in the midft whereof he is plac'd ; which Ar- rangement of Circumflanccs, depends on the Providence of God : whence Converfion alfo depends on him. See Con- version.

The Circumflances of the Actions of Men, are exprefs'd in this Latin Verfe.

Jgilis, quid, ubi, qttibus auxiliis, cur, quomodo, quando.

gllis, who, denotes the Quality, State, Age, Sgc. of the Perfon. Stmd, what, the greatnefs, fmallnefs, multitude, fewnefs, tgc. of the thing. Ubi, where, the Place, £>uibus Auxiliis, with what Afliftances, the Infttuments, Means, &c. Cur, why, on what Account, with what View, giiomodo, how, the Quality of the Afiion, as to Intenfion or Remiff- nefs, Defignednefs or Cafualty, Secrecy or Opennefs. Quan- do, when, the Time ; as on a Holiday, at the Hour of Pray- er, iSc.

CIRCUMSTANTIBUS, in Law, is us'd for the fupply- ing, and making up the Number of Jurors, (in cafe any im- panell'd appear not ; or appearing, be challeng'd by either Party) by adding to them fo many of the Perfons prefent, or ftanding by, as will ferve the turn. See Jury, and Juror.

CIRCUMVALLATION, in Fortification, a Line, or large Trench, made around a Camp ; in rhe befieging of a Town. See Line, Fortification, &c.

This Trench is to be a Cannon-fhot diftant from the Place, ordinarily, about 12 Foot broad, and feven deep. It is bor- der'd with a Parapet, and flank'd with Redoubts, or little Forts, erefied from Space to Space. It ferves both to pre- vent any Succour from being fent into the Place, to keep in Deferters, and prevent Incurfions of the Enemy's Garifon.

Care muft be taken that the Line of Circvmvallation never pafs by the Foot of an Eminence ; left the Enemy feizing on the Eminence, lodge his Cannon, and command the Line.

The Word is form'd from the Latin circuit!, about and vallum.

CIRCUMVOLUTIONS, in Architeaure, the Turns of the Spiral Line of the Ionic Volute. See Volute.

The Word comes from the Latin Circumvolvere, to turn around ; and is alfo apply'd to the Turns of a wreath'd or twilled Column. See Column.

CIRCUS, in Antiquity, a large Building, either round, or oval ; us'd for the exhibiting of Shews to the People. See Spectacles, Circensian Games, Sic.

The Roman Circus, was a latge Place, or Square, arch'd at one End ; incompafs'd with Porticos, and furniih'd with Rows of Seats, plac'd afcending over each other.

In the middle was a kind of '"Banquette, or Eminence, with Obelilks, Statues, and Pofts at each End. This ferv'd 'em for the Courfes of their Big<e and guadrigs. See Big*, i$c.

There were no lefs than ten Circus's at Rome : the larg- er! was that built by the Elder Tarquin, called Circus Maxi- mus ; between the Aventine and Palatine Mounts. Pliny fays, it was enlarg'd by J. Ctefar, fo as to take in no lefs than three Stadia in Length, and one in Width.

The moft magnificent Circus's were thofe of Auguflus and Nero. There are flill fome Remains of the Circus's, both at Rome, at Nifmcs, and other Places.

The Romans were exceflively fond of rhe Games exhibit ed in the Circus, witnefs that Verfe in Juvenal,

Atque dims tantum res auxins optat,

'Panem ££? Circenfes ,-— —

Some