Page *125

ci
(*ait )
iadmill, Le. ' See CR.&N E,
,is applied by fomne Nagu-
7ut', Moesand other
Se -hiUSGU, USHROOM,
a Peron, ~skill'd in Trees,
#a. See T~atE.
Mfs' extent than B otanifl.
i,Ueea~cinA of Ihady Bower
e Airin. See GARDEN.
ato difitfe, by reafon -their
unwholefome-They are
I only of the Branches of
born up by ftrong Lattice-
wh make Galleries, Halls,
-ally covered.
,xrbours are formed, are u-
ch Lime-Trees; in regard
ir great quantity of fmall
ad: the lower parts are filled
icnts are made of Lattice-
oi-rails Circles and Arches
ymake u e of finall Fillets
I made firait, are wrought
Wire.
the l~atin?, 4'rCus, a Bow1.
i a Secret ; and is therefore
:cks and Impoffors in Medi-
:eand 17,aud under a pre~-
egions of ircana.
wA Compofitions, under the
are
Preparation of red Preci-
th Spirit of N1itre, and re-~
d again, till a red Powder
ed in ;Water, and the Water
of Wine put to the Powder 5
lade : which leave a Powder,
;of good ufe in the Gout,
schiefly by Stool.
Fan Amalgama of Mercury
fNitre : the Nitre being
:tter is wetted with Spirit
away ; and this for fieveral
none : what remains is ufed
sthe ,fntihe~icum :Poterii,
Lsa Sudorific. See A N TI-
iar'd of Caput Mortuum of
lot Water, filtrating, and e-
n leaving it to 1hoot.
r Panacea diioicata; is ex-
fic-The Recipe was pur-
'larsi by that great Virtuofo
hat Prnce's Phyfician, writes
icondriacal C ares, continu-
ne, Scury  'c
1g, a fiaty A~rch or part of
Dins of a Vaulti to Pupport,
:e VAULT.
d Buttreffcs. See BUT-
of arc and bouster, to a-but
rt of any curve Line i e gr.
See CuVRvE.
the Circumference thereof,
-Suclh is AB (Tab. GEo-
and CIRCUMI.tRENCE.
;sthe two Extremes of the
the Perpendicular rais'd in
we ofthe Arch. See CHIORD
Archbes_-t know their
dhaving its -Centre in the
divided into 350 Derees 5
ii to the Number of thofe
15an, Arch is faid to be of
e DEG.R EE. Hence
-bes of the fame or equal
Number 'of: Degrees.  See
equal Chords fubtend equal
archcs intercepted between
Arborift is an appellation of lels extent than Botanifi.
.See BOTANYi &C..
ARBOUR,among Gardeners,>cea kind of fhady Bower
or Cabinet, contrived totake the Airin. See GARDEN.
Arbours are now gone much into difiufe, by reafon their
Seats, apt to be moifi, are unwholefome-They are
diftinguilh'd into natural and artifkcial.
::  Natural xrbours, are formed only of the Branches of
-:Trees, interwoven artfully, and born up by ftrong Lattice-
work, Poles, Hoops, &fc. which make Galleries, Halls,
porticoes, and green Vifto's naturally covered.
The Trees wherewith there Arbours are formed, are u-
fually the Female Elms, or Dutch Lime-Trees; in regard
they eafily yield, and by their great quantity of fmall
Boughs, form a thick Brulh-wood: the lower parts are filled
.up with Horn-beam.
-Artificial Arbors,. and Cabinets are made of Lattice-
work, born up by Standards, Crofs-rails, Circles and Arches
of Iron. For which purfofe they make ufe of finall Fillets
of Oak, which being planed and made firait, are wrought
in.Checkers, and faitened with Wire.
ARC, or AR K. See ARPCH .
The Words are formed from the latin, /rcus, a fow.
ARCANUM literally fignifies a Secret; and is therefore
very pertinently applied by Quacks and Impoffors in Medi-
cine, who conceal their Ignorance and 1kaud under a pre-
tence ofSecrecy-IHence Legions of Urcana.
There are alfo flanding officinal Compofitions, under the
Denomination of Arcana: fuch are
The Arcanum Corallinum, a Preparation of red Preci-
pitate; made by diffilling it with Spirit of Nitre, and re-
Eeatisig the Diflillation again and again, till a red Powder
be procured. This Powder boiled in Water, and the Water
poured off, and tartariz'd Spirit of Wine put to the Powder;
two or three Cohobations are made: which leave a Powder,
much like the Prince's Powder; of good ufe in the Gout,
Dropfy, Scurvy, Efc. It operates chiefly by Stool.
Arcaltim 7oviale, is made of an Amalgama of Mercury
and Tin, digefied in Spirit of Nitre : the Nitre being
drawn oA the remaining matter is wetted with Spirit
of Wine, and the Spirit burnt away; and this for feveral
times till the pungent Tafie is gone: what remains is ufed
nmuch withithe fame Intentiois asthe Afntiheticum Poterii,
and is recommended by fome as a Sudorific. See ANTI-
HECT IC CM.
Arcanum duplicatum is prepar'd of Caput Mortuum of
Aqua fortis, by diffolving it in hot Water, filtrating, and e-
vaporating it to a Cuticle; then leaving it to Ihoot.
The zrranum duplicatum, or Panacea duplicata is ex-
tolled as a Diuretic, and Sudorific-The Recipe was pur-
chafed at the expence of 5op Dollars, by that great Virtuofo
theDuke of Holflein Schroder, thatPrince's Phyfician, writes
wonders of its great ufes in Hypocondriacal Caies, continu-
ed and intermitting Fevers, Stone, Scurvy, Ec.
ARC-BouTANT, in Building, a fiat Arch or part of
an Arch abutting againfi the Reins of a Vault, to fupport,
and prevent its giving Way. See VAULT.
fC-boutants are only arch'd Buttreffcs.  See BUT-
TaEsst.
The name is French; form'd of arc and bouter, to a-but
ARCH, ARK, AR cJs, a part of any curve Line i e.gr.
of a Circle, Ellipfis, orthe like. See CuaRvE.
. ARC I of a Circle is a part of the Circumference thereof,
lefs than a halfior Semicircle-Such is AB (Tab. Gao-
METRY, fig. 27) See CtRChE and CIRCUMtERFNCE.
The Bafe or Line that joins the two Extremes of the
Arch is called'the Chord; and the Perpendicular rais'd in
the middle of thAt Line, the Sine ofthe Arch. See CHORD
and SINE.
All Angles are meafured by Arches---to know their
Quantity, an Arch is defcribed, having its Centre in the
Point of the Angle. See ANGLE.
Every Circle is fuppofed to be divided into 360 Degrees ;
and an Arch'is eflimated according to the Number of thofe
Degrees it takes up-    Thus an, Arch is Laid to be of
3o, of 8o, of Ioo Degrees. See DEGREE. Hence
Equal ARCHEs are fuch Arches of the fame or equal
Circles, as contain the fame Number of Degrees.  See
E     A L-Hence
ini the fame or equal Circles, equal Chords fubtend equal
Arches-And hence, again, Archcs intercepted between
parallel Chords are equal.
A RC
A Radius, CE, 94.98. which biffies the Chord in D; does
alMo biffie& the4rch, in E hand is perpendicular to theChord
and on the cohtrary-And hence the Problem, to biffea
an Arch is folved by drawing a Line AB  perpendicular to
the Chord in P.
Similar AEcsrts are thofe which contain the fame Num-
ber of Degrees of unequal Circles. See SIMItAv.-Such
are the Arches A B and f DE, fig. 87.
Two Radii being drawn from the Centre of two concen-
tric Circles; the two Arches intercepted between 'em,
bear the fame Ratio to their refpecive Peripheries; and
alfo the two Sedors to the Areas of their refpctive Circles.
See ANGLE.
The Diffance of the Centre of Gravity of an A1rch of a
Circle, from the Centre of the Circle, is a third Proportio-
nal toa third part of the Periphery and the Radius. See
CE N TRE of Gravity.
For the Sines, Tangents, Fic. of Arches. See SINE*
TANGENT, SfC.
ARCH in Aflronomy-Diurnal ARCH of the Sun, is
part of a Circle parallel to the Equator, defcribed by the
Sun in his Courfe betwixt rifing and fetting, See DIURNAL,
D AY, E5c.
His no6turnal Zrc1 is of the fame kind; excepting that
it is defcribed betwixt his fetting and riling. See NIGHT,
RISING, &C.
The Latitude and Elevation of the Pole are meafured by
an Arch of the Meridian: The Longitude, by an Arch of
a parallel Circle. See ELEVATiON, LATLiTUDE, LON-
GITUDE, VfC. .
ARCH of Progref/ion, or fDire[lion, is an Arch of the
Zodiac which a Planet f-ems to pafs over, when its Mo-
tion is according to the Order of the Signs. See DImEc-
TION.
The ARC i of Retrogradation is an Arch of the Zodiac,
defcribed while a Planet is retrograde, and moves contrary
tothe Orderof the Signs. See RETROGRADATION.
ARCE  of Station.  See STATION and STATIONARY.
AR cri between the Centres is anArcbasAI(Tab. AsT ao-
NOMjY, fig. 35.) paring from the Centre of the Moon's
Shadow, A, perpendicular to her Orbit GH.See ECLIPSE.
If the Aggregate of the Arch between the Centres Al,
and the apparent Semi diameter of the Moon, be equal to
the Semi-diameter of the Shadow; the Eclipfe will be
total without any duration: if lefs, total with fome dura-
tion ; and if greater, yet lefs than the Sum of the Semi-
diameters of the Moon and the Shadow, partial-
ARCH of VTifion is the Sun's depth below the Horizon, at
which a Star, before hid in his Rays, begins to appear a-
gain. See Poetical RISINm.
ARcu , in Architedure, is a Concave Building, rais'd with
a Mould bent inform of the Arch of a Curve, and fervine as
the inward Support of any Superfiruaure. See BUILD-
ING.
An Arch, fays Sir Henry lfotton, is nothing but a nar'-
row or contrafted Vault; and a Vault, a dilated Arch. See
VAULT.
,4rches are ufed in large Intercolumnations of fpacious
Buildings ; in Porticos, both within and without 'Fem-
ples; in publick Halls, as Ceilings, the Courts of Palaces,
Cloifiers, Theatres and Amphitheatrcs.  See PORtICOi
THEATRE, CEILING, 'C.
They are alfo ufed as Buttreffes and Counter-forts to
fupport large Walls laid deep in the Earth, for Foundations
of Bridges and Aquadufs, for triumphal Arches, Gates,
Windows, Cc. See BUTTRESS, ARc-boutanZt; &C.
Arches are either circular, elliptical, orflrait-
Circular ARCHES are of three kinds, viZ.-xfa, Semi-
circular, which make an exat Semicircle, and have their'
Centre in the middle of the Chord of the Arch.
2dly, Scheme, which are lefs than a Semicircle, and con-
fequently are flatter Arches; containing fome, go Degrees,
others 7c, and others only 6o.
3dly, Arches of the third and fourth Point, as Come of
our Workmen call them; tho' the Italians call them di
terzo and quarto acuto, becaufe they always meet in an
acute Angle at top-Thefe confide of two Arches of i
Circle ending in an Angle at the Top, and are drawn
from the Divifion of a Chord into three or four Parts, at
pleafure-Of this kind are many of the Arches in old
Gothick Buil4ings; but on account, both of their Weaknefs
and Unfightlinefs, they ought, according to Sir Henry
Wotton, to be forever excluded out of all Buildings.
Elliptical ARCHES confift of a Semi-Ellipfis; and were
formerly much ufed inflead of Mantle-trees in Chimneys-a
Thefe have commonly'a Keyflone andChaptrels or Impofis.
Strait ARCims, are thofe whofe upper and under Edges
are firait; as in the others they are curved i and thofe two
Edges alfo parallel, and the Ends and Joints all pointing
towards a Center-Thefe are principally ufed over Win-
dows, Doors, Fc             1,
[E K J
.K,"