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Tbt Dberine and tyfe of Arches is well delivered by Sir
YIenry Motto*, in the following Ylbeorems.-i 1, All Matter,
-unlefs impeded, tends to the Center of the Earth in a per-
pendiciilar Line. See DESCENT, GRAVITY, CENTRE, hC.
eidly, All folid Materials, as Bricks, Stones, Lèc. in their
ordiay retangular Form, if laid in Numbers, one by the
Side of another, in a level Row, and their Extreme
ones fuflained between two Supporters ; thofe in the
middle will necethriiy fink, even by their own Gravity,
much more if prefs'd down by any fuperincumbent Weight-
To make them fand, therefore, either their Figure or their
Pofition muft be altered.
3dly, Stones, or other Materials being figured Cuneatim,
i. e. Wedge-wife, broader above than below, and laid in a
level Row, with their two Extremes fupported as in the
preceding Theorem; and pointing all to the fame Center i
none of them can fink, till the Supporters or Butments give
way, becaufe they want room in that Situation to defcend
perpendicularly. But this is but a weak Strudure 5 in re.
gard the Supporters are fubje& to too much Impulfion,
efpecially where the Line is long; for which reafon, the
Form of firait Arches is feldom ufed, excepting over Doors
'and Windows, where the Line is fhort-In order to for-
tify the Work, therefore, we mul not only change the Fi-
gure of the Materials, but alfo their Pofition.
4thlyIf the~laterialsbe fhaped wedge-wife, and be difpo-
fed in form of a circular ArcAb, and pointing tofome Center;
in this Cafe, neither the pieces of the faid Arch can fink
downwards, for want of room to defcend perpendicularly;
nor can theSupporters orButments fufferfo muchViolence as
in the precedent flat Form: for the Convexity will always
makethe incumbent Weight rather refi upon the Supporters,
than heave them outwards: whence this Corollary may be
fairly deduced, that the fecurell of all the Arches abovemen-
tion'd is the Semi-circular i and of all Vaults, the Hcmi-
fpherical.
5thky, As Semi-circular Vaults, rais'd on the whole
Diameter, are the firongerf; Co thofe are the molt beauti-
ful, which keeping to the fame height, are yet diftended,
one fourteenth part longer than the faid Diameter: which
addition of width will contribute greatly to their Beau-
ty, without diminilhing any thing confiderable of their
Strength.
It is, however, to be obferv'd, that according to Geome-
trical Striflnets, to have the firongefi Arches, they mufl
not be Portions of Circles, but of another Curve, call'd the
Catenaria, whofe Nature is fuch, that a number of Spheres
difpos'd in thisform, will fiftain each other, and form an
Arch. See CATE NARI1A.
Dr. Gregory even fhews, that Arches confirufled in other
Curves, only Rland or fullain themfeives by virtue of the
Catenaria contain'd in their thickness; fo that were they
made infinitely flender or thin, they mull tumble of courfe;
whereas the Catenaria, tho' infinitely flender, mull Rand, in
regard no one point thereof tends downward more than any
other. tPhilofoph. l7ranfaf. N9. 2 31.
See further of the lTheory tinder the Article VAULT.
Arches are fuflain'd byi Impoils. See IMPOSTS.
AR c H is particularly ufed for the Space between the two
Peers of a Bridge. See PEEP. and BR. I DG E.
The chief or Malter-Arcb is that in the middle ; which
is widenl, and ufuallv highelt, and the Water under it dee-
pef : being intended for the patfage of Boats or other Vef-
fels-W    e read of Bridges in the Eaft, which confill of
300 Arches.
ARcH-Stone. See KEY-Stone.
glriumphal AR c H, is a Gate, or Pafrage into a City,mag.
nificently adorned with Architeture,Sculpture, Infcriptions,
fI.c. which being built of Stone or Marble, ferves not only
to adorn a Triumph, at the Return from a viltorious Ex-
pedition, but alfo to preferve the Memory of the Conque-
ror to poflerity. See TR aI M P I{.
The moft celebrated Triumphal Arches, now remaining
of Antiquity, are that of 2itus, of Septimus Severus, and of
Conftantine, at Rome.
ARCII, in the Scripture Senfe. See ARK .
AR Cii, or APc II , isalfo a Term without any meaning of
itdelf, but which becomes very fignificant in compofition with
other Words: It heightens and exaggerates them; and has
the Force of a Superlative, to {hew the greateft Degree or
Eminence of any thing.
Thus wetfay Arch-fool, .4rch rogue, Cc. to exprefs Folly
and Knavery in the utmoft Degree-So alfo Arch-Trea-
furer, A~r&b Angel, Arch-B;ihop, Arch-Heretick, Jec. to
denote fuch as have a Pre- eminence over others.
The Word is form'd of theGreek ^¢xu, beginning; whence
cpo;, princets, fl~mus.
A R C
In Evglijb we ifiually cut of* the
tho' to very ill purwpoe; the W(
joined, founding much hariher on ,
wou'd do were it preferv'd entire,
Languages. See ANoMALoUs, CoNT]
ARCH&US, on obfcure Term, ul
Antient Chymills, to exprefs I know
Life and Motion ;- the Caufe of all th,
ferve in Nature. See LIFE.
Hence, as they differ in their Idea
the Term Archieus becomes applil
Things: Tho moyl of'em conceive
Fire. See FIRE.
Some ufe Archous to denote the Fin
of the Earth, to which they. afcril
Metals and Minerals, and which the
Principle of Life in Vegetables $ee
Others by the Word Archeus mnea
Spirit, difufed throughout the whole
Caufe of all the Phanomena in Na
Ji jAATflfl,  *v.nAJltM4.  tV.
Others, inftead of Archus, chufe to call it the
. Mundi; and others the Vuica or Heat of the Eari
A-. xg.-1 A edA i- O
They add, that all Bodies have their Share
Arcbiens ; and when this is corrupted, it produce,
fes, which they call Archeal-Jiftaf/es.
They likewifc attribute Ideas to it ; which for td
fenn th.-ucal l      r~cin  depar eI Z A.
*w$~~~~~ I'9 '*  "F"V*Bss.vx Avo
eWord is derived from di%, Principle; this
being the Principle and Source of all the Ege&s, in
ture. See PRINCIPLE.
Helmont is a great Afferter of the Dogma ofan A.rch
"No Poifon, fays he, can a&c on a Carcafs t if, therefbr
"have any Effe&, 'tis by means of the Archcus. He a
"that if any heterogeneous Body happen to be Pre
"to the Archeus; it rifes into a fervour, endeavour
"expel the hollile matter; and, in order to that, en
" all the force of the Body-To cure any Difeafe, ti
"fore, is to pacify, and compofe this Archeus. This
" chaeus, he holds, is irritated at the leall appearance of
I' thing heterogeneous; and as its Office is to watch ovet
" Health, and Safety of the whole Body; it is excit
"the very Shadow of the Enemy, calls its Forces to
"Charge, raifes Fevers, &c. All, therefore, require
an universal Medicine, is fomething that may readily
"cify, and lay this Unnatural Fever upon all occafic
This Doftrine of Helmont, !Boerhaave obferves, would
be Co abfurd, did he not afcribe Underflanding to this
cheus: fetting this afide, the Principle which renders
fons deadly, and Remedies beneficial, is the Circulatic
the Blood. See CIRCULATION and BLOOD.
ARCH-ANGEL, an intelle.ual Subflnce or Ange
the eighth Rank among the blefied Spirits which corn
the Celeftial Hierarchy.  See ANGEL and HIER'
CHY.
The Word is compounded of the Greek apXis Prince
CrH4AxO Angel.
ARCHBISHOP, ARCH1IEPISCOPUS, a metropol
Prelate, having feveral fufiagan Bifhops under him.
BISHOP, SUFFa AGAN, FC.
Archbif hops were not known in the Eail, till about
Year 32o; and tho' there were fome Coon after thisl
had the Title, yet that was only a perfonal Honour
which the Bifhops of confiderable Cities were diffingu
cd-It was not till of late that ArchbiJhops becd
Metropolitans, and had Suffragans under them. See b
TROPOLITAN.
A#thanafus appears to be the firil that ufed the T
Archbisfhop, which he gave occafionally to his Predeceff
Gregory Nazianzen, in like manner, gave it to *ithan4
not that either of them were entitled to any Jurifdiaion
even Preedence.' in virtue~ ithpre.nr --
Among the LatinsIfdore HIfpalenfs istl
fpeaks of Archbihops. He diflinguifhes fot
Degrees in the Ecclefiafilical Hierarchy, viz.
Archbijhops, Metropolitans, and fBijbops. See P
&C.
England is divided into two Archbizboprick1
ces. See ARCHBISHOPRICK.
ARCHBISHOPRICK, ARCEII EP ISCOP A -
nity of Archbifhop j or the Province under his
See ARCHIBISHOP.
There are two Archbilhopricks in  rgland,
terbury and Tork; the Prelates whereof are
mates and Metropoltans.  See Pa a ATEr and
L IT&N,
A R C
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