Page:Cyclopaedia, Chambers - Volume 1.djvu/171

 ARC

C116 ) ARC

The Do£lfineandUfeof^-^w is well delivered by Sir Henry Wbtton, in the following 'Theorems. — ift, All Matter, unlefs impeded, tends to the Center ot the Earth in a per- pendicular Line. See Descent, Gravity, Centre, l£c.

idly, All folid Materials, as Bricks, Stones, £Sfa in their ordinary rectangular Form, if laid in Numbers, one by the Side of another, in a level Row, and their Extreme ones fuftained between two Supporters 5 thofe in the middle will neceffarily fink, even by their own Gravity, much more if prefs'd down by any fu per incumbent Weight — To make them ftand, therefore, either their Figure or their Pofition mull: be altered.

2". e. Wedge-wife, broader above than below, and laid in a level Row, with their two Extremes fupported as in the preceding Theorem j and pointing all to the fame Center j none of them can fink, till the Supporters or Butmentsgive way, becaufethey want room in that Situation to defcend perpendicularly. But this is but a weak Structure ; in re- gard the Supporters are fubjeft to too much Impulfion, efpecially where the Line is long j for which reafon, the Form of ilrah Arches is feldom ufed, excepting over Doors and Windows, where the Line is fhort In order to for- tify the Work, therefore, we muft not only change the Fi- gure of the Materials, butalfo their Pofition.
 * dly, Stones, or other Materials being figured Cuneatim t

4thly,If theMatcrialsbe fhaped wedge-wife, and bedifpo- fed in lorm of a circular Arch, andpointing tofome Center 5 in this Cafe, neither the pieces of the faid Arch can fink downwards, for want of room to defcend perpendicularly 5 nor can theSupporters orButments fufferfo muchViolence as in the precedent flat Form : for the Convexity will always makethe incumbent Weight rather reft upon theSupporters, than heave them outwards : whence this Corollary may be fairly deduced, that the fecureflofall the Arches abovemen- tion'dis the Semi-circular j and of all Vaults, the Hcmi- ifpherical.

5thly, As Semi-circular Vaults, rais'd on the whole Diameter, are the ftrongeft ; fo thofe are the moil beauti- ful, which keeping to the fame height, are yet diftended, one fourteenth part longer than the laid Diameter : which addition of width will contribute greatly to their Beau- ty, without diminishing any thing confiderable of their Strength.

It is, however, to be obferv'd, that according to Geome- trical Striclnefs, to have the ftrongeft Arches, they muft not be Portions of Circles, but of another Curve, call'd the Catenaria, whofe Nature isfuch, that a number of Spheres difpos'd in thisform, will fuftain each other, and form an Arch. See Catenaria.

Vt. Gregory evenfhews, that Arches conftruflcd in other Curves, only ftand or fuftain themfeives by virtue of the Catenaria ccntain'd in their thkknefs ; fo mat were they made infinitely (lender or thin, they muft tumble of courfe; whereas the Catenaria,tho' infinitely ilender, muft ftand, in regard no one point thereof tends downward more than any other. c Philofoph. < TranfaB. N°. 231.

See further of the theory wider the Article Vault.

Arches are fuftainM byilmpofts. See Imposts.

Arch is particularly ufed tor the Space between the two Peers of a Bridge. See Peer andBRiDGE.

The chief or Mafier-Arch is that in the middle ; which is wideft, and ufually higheft, and the Water under it dee- peft : being intended for the paflage of Boats or other Vef-

f e ls We read of Bridges in the Eaft, which conlift of

300 Arches.

ARcn-Stone. See KzY-Stone.

Triumphal Arch, is a Gate, or Paffage into a City,mag- nificently adorned with Architeciure.Sculprure, Infcriptions, l$c. which being built of Stone or Marble, ferves not only to adorn a Triumph, at the Return from a victorious Ex- pedition, but alfo to preferve the Memory of the Conque- ror to pofterity. See Triumph.

The moft celebrated Triumphal Arches, now remaining of Antiquity, are that of 'Titus, of Septimus Severus, and of Confiantine, at Rome.

Arch, in the Scripture Senfe. See Ark.

Arch, or ARcm,isalfo a Term without any meaning of itfelf, but which becomes very fignificant in compofition with other Words: It heightens and exaggerates them 5 and has the Force of a Superlative, tofhew the grcateft Degree or Eminence of any thing.

Thus we fay Archfao], Arch rogue, %$c. to exprefs Folly

and Knavery in the utmoft Degree So alfo Arch-Trez-

furer Arch-&ng^ ^c&-Bifhop, ^rc^-Heretick, $$c. to denote fuch as have a Pre- eminence over others.

The Word is form'dof thtGreek *$%*, beginning; whence Wfc frincep, fumtnuu

In Englifh we ufually cut off" the final ;, from Arch' tho* to very ill purpofe 5 the Words wherewith U7 join'd, founding much harfher on that fcore than the'* wou'd do were it prefer v'd entire, as it is in mift $.J Languages. See Anomalous, Contraction, &c.

ARCHjEUS, onobfeure Term, ufed chiefly amonp t i Antient Chymifts, to exprefs I know not what principle f Life and Motion -, the Caufe of all the Effects which we oh' ferve in Nature. See Life.

Hence, as they differ in their Ideas of a vital Cauf c the Term Archms becomes applied to very diff cren * Things : Tho moft of 'em conceive it of the Nature of Fire. See Fire.

Some ufe Archteus to denote the Fire lodg'd in the Centre of the Earth 5 to which they afcribe the Generation of Metals and Minerals, and which they believe to be ihc Principle of Life in Vegetables. See Central, £fc.

Others by the Word Arch£US mean a certain univerfal Spirit, diffufed throughout the whole Creation, the acliw Caufe of all the Phenomena in Nature. See Spir u jEther, Medium, &c.

Others, inftead of ArchdSUS., chufe to call It the Afiim Mundi i and others the Vulcan or Heat of the Earth. See Anima, Mundi, Sec.

They add, that ajl Bodies have their Share of this Arch&us ■-, and when this is corrupted, it produces Difea- fes, which they call Arch#al- e Difeafes.

They like wife attribute Ideas to it j which for this E.ea« fon they call Arcbaal Ideas. See Idea.

The Word is derived from *eX"» Principle ; r this Fire being the Principle and Source of all the Effects in Na- ture. See Principle.

Uelmont is a great Afferter of the Dogma ot&n Arcfatti-* " No Poifbn, fays he, can a£l on a Carcafs i if, therefore, it 11 have any Effect, 'tis by means of the Archaws. He adds, " that if any heterogeneous Body happen to be prefent " to the Archaus ; it rifes into a fervour, endeavours to " expel the hoftiie matter ; and, in order to that, exerts

11 all the force of the Body To cure any Difeafe, there-

" chaus, he holds, is irritated at the leaft appearance of any 11 thing heterogeneous 5 and as its Office is to watch over the " Health, and Safety of the whole Body ; it is excited at " the very Shadow of the Enemy, calls its Forces to the " Charge, raifes Fevers, &c. All, therefore, required to " an univerfal Medicine, is fomething that may readily pa- " cify, and lay this Unnatural Fever upon all occafions." This Doftrine of Helmont t Boerhiaveob&vvts, would not be fo abfurd, did he not afcribe Underftanding to this Ar*. chilis: fetting this afide, the Principle which renders Poi- fons deadly, and Remedies beneficial, is the Circulationof the Blood. See Circulation and Blood.
 * ' fore, is to pacify, and compofe this Archdzus. This/r-

ARCH-Angel, an intellectual Subftance or Angel in the eighth Rank among the bleffed Spirits which compofe the Celeftial Hierarchy. See Angel, and Hierar- chy.

The Word is compounded of the Greek opjf.Sf, Prince and

ttfyihaf Angel.

ARCHBISHOP, Archiepiscopus, a metropolitan Prelate, having feveral fuffragan Bifhops under him. See Bishop, Suffragan, £i?c.

Archbifhops were not known in the Eaft, till about the Year 520 } and tho* there were fome foon after this who had rhe Title, yet that was only a perfonal Honour by which the Biftiops of confiderable Cities were diftinguilh-

ed It was not till of late that Archbifbop became

Metropolitans, and had Suffragans under them. See Me- tropolitan.

Athanafius appears to be the firft that ufed the Title Archbifbop, which he gave occafionally to his Predeceflor ; Gregory Nazi anzen, in like manner, gave it to Athanafius: not that either of them were entitled to any Jurifdiftion, or even Precedence, in virtue thereof.

Among the Lathis, Jfidore Hifpalenfis is rhe firft that fpeaks of Archbifhops. He diftinguifhes four Orders or Degrees in the Ecclefiaftical Hierarchy, viz. Patriarchs, Archbijbops, Metropolitans, and Sijbop. See Patriarch,

England is divided into two Archbifhoprichs^ or Provin- ces. See Archbishoprics.

ARCHBISHOPRICK, Archiepiscopatvs, rfieDig- nity of Archbifhop; or the Province under his Jurifdichon. See Archbishop.

There are two Archbifhopricks in England, viz of Can- terbury an&Tork. ; the Prelates whereof are call'd 9ri' mates sad Metropolitans. See Primate and Metro? '

tITAN.

The