J3 R I


wvater muft be c6fried off, and the reft kept dry and piled:
that fide of the river where you are to Work IS to be inclo-
fed with coffer-dams, and the current to have its liberty on
the other fide. See FOUNDATION. Palladio's dire&ions
are, fir*t, to make choice of that place in a river which has
the leaft depth of water, and where the ground is even and
firm , especially rock or gravel ftone; fecondly, to avoid
thofe places where there are voragos, or whirlpools, and
where the bottom is foft fand or gravel, in regard fuch mat-
ters are eafily carried away by the violence of water, which
in time alters the bed of a river, and faps the foundation of
the peers; thirdly, to pitch on a ftreight part of a river,
fince otherwife the turns and windings being worn away in
time, the bridge is in danger of being left infulate; befides
being liable to be choaked up with the filth, and other mat-
ters commonly gathered in the turns of rivers.
BRIDGES are either built of flone or timber, according as
there is a conveniency, or plenty of the one material or the
other in the place.
Stone-BR ID GE s, are compofed of peers, arches, and butments,
made of hewn lone, fometimes alfo intermixed with brick;
as, the bridge of Tholoufe, the plinths whereof are of lone,
as alfo the quoins of the arches, and foome bonding courfes,
and copings; but the reft, as the arches, walls, and but-
ments, of brick.
l'ooden-Ba ID GE S, called by the Latins, pontes fublicii, confift
of beams and joifts fuftained by punchions, well cramped
and bound together.
Sturmius has a differtation exprefs on the ftru6lure of a
wooden-bridge: Difp. de Ponte Sublicio. Francof. 1709
Rujhen-BR IDGE, pont de jemc, is made of large theaves of
ruPhes growing in marfiy grounds, which they cover over
with boards or planks. They ierve for crofling ground that
is boggy, miry, or rotten.
The Romans had alfo a fort of fubitancous bridges, made by
the foldiers, of bbats, or fometimes of caks, leathern bot-
tles or bags, or even Qf bullocks bladders blown up, and faff-
ened together, called afqjgefri. Pitifc. L. Ant. T: 2. P. 464.
feq. voc. Pontes. Du Cange GloV. Lat. T: I. p. 350. M.
Couplet gives the ftru6ture of a portable bridge, 200 foot
long, eafily taken afunder and put together again, and which
forty men may carry.-Aid. Du Hamel Hp. Reg. Acad. Sci-
en.  3. feix 5. c. 4. p. 273.
Frezier fpeaks of a wonderful kind of bridge at Apurima in
Lima, made of ropes, formed of the bark of a tree.-bd.
Frez. Voyag. South-Sea, p. 184.
Pendent, or Hanging, called alfo Philofaphical BRIDGES, are
thofe not Supported either by polls or pillars, but hung at
large in the air, only fuffained at the two ends, or but-
kents.-Inftances of fuch bridges are given by Palladio, and
others.-Yid. Vogels Modern. Ba&u-Kunf. Tab. 26. feq. Wolf.
L. Math. p. 277. voc. Brucke. Kirch. Afind. Subterr. 1. I.
{. 3. 1- I- P. 14-
Dr. Wallis gives the defign of a timber-bridge, feventy foot
long, without any pillars, which may be ufeful in fome pla-
ces where' pillars cannot conveniently be ereled. Philof
Tranf. No i63. p. 714. Dr. Plot affures us, that there was
formerly a large bridge over the caftle-ditch at Tutbury in
Staffordf~hire, made of pieces of Timber none much above a
yard long, and yet not fupported underneath, either with
pillars, or arch-work, or any other fort of prop whatever.-
("id. Plot Nat. 1Ax7. Stafford. c. 9. ß. 88. p. 383.
Draw-BR I D G E, Pons fubdudarius, is fuch a one as is made
fail only at one end, with hinges; fo that the other end may
be lifted up; in which cafe the bridge ftands upright, to hin-
der the paffiage of a moat, or the like.
There are others made to draw back, to hinder the paffage,
and to thruft over again to afford a pafiage. And others,
which open in the middle; half of which turns away to one
fide,-and the other to the other; being joined again at plea-
fure: but thefe have this inconvenience, that one half of
them remains on the enemy's fide.
The Marquis de l'Hopital has given the conftrution of a
curve, in which a weight will always be a counter-balance
to a draw-bridge; which the younger Bernoulli has fhewn
to be no other than the cycloid.-Fid. A. EPrud. L; f an.
1695- p. 56. 56-faeq.
Flying-B RID GE, Pant va/ant, or Pons duflarius, an appellation
given to a bridge made of pontoons, leathern boats, hollow
beams, cafks, or the like, laid on a river, and covered with
planks for the paffage of an army.
Flying-BR I D G E, Pant volant, more particularly denotes a bridge
compofed of one or two boats joined together, by a fort of
flooring, and furrounded with a rail or balluifrade; having
alfo one or more mafts, to which is fattened a cable, fup-
ported at proper diftances by boats, and extended to an an-
chor, to which the other end is falened, in the middle of
the water. By which contrivance, the bridge becomes move-
able, like a pendulum, from one fide of the river to the o-
ther, without other WDlp than the rudder.-Sucb bridges fome-
times alfo confift of two lories, for the quicker paffage of a
great number of men; or that both infantry and cavalry
may pas at the fame time.-Davil.
Flying or Fatiq -BRIDGt, is ordinarily made of two fmall


D E G


bridges, lid one over the other, in fuch nianner, as that the
uppermoft Iretches and runs out, by the hep of certain
cords running through pullies placed along the fides of the
under-bridge, which pufh it forwards tiU the end of it joins
the place it is defigned to be fixt on.
When thefe two bridges are ftretched out at their full length;
fo that the two middle ends meet, they are not to be above
four or five fathom long, becaufe if longer they will break.
Their chief ufe is for furprizing out-works, or polls that
have but narrow moats.
In the memoirs of the royal academy of fciences, we find a
new contrivance of afioating-bridge, which lays itfelf on the
other fide of the river.-Vid. H1y. Jcad. R. Scienc. an. I713.
P. I04.
BR ID G E   communication, is a bridge made over a river; by
which two armies or forts, Separated by the river, have a
free communication with one another.
BRIDGES of boats, are either made of copper, or wooden
boats faftened with flakes, or anchors; and laid over with
planks. See BOAT.
One of the molt notable exploits of Julius Cmfar, was the
expeditious making a bridge of boats over the Rhine: mo-
dern armies carry copper boats, called pontoons, to be in rea-
dinefs for the making bridges: feveral of thefe being joined
fide by fide, till they reach acrofs the river, and planks laid
over them, make all plain for the men to march on. See
PONTOON.                               V
There are fine bridges of boats at Beaucaire, and Rouen,
which rife and fall with the water; yet that at Seville is faid
to exceed them both.
The bridge of boats at Rouen, built in lieu of the lately
lone-bridge eredted there by the Romans, is reprefented by
a modern writer, as the wonder of the prefent age; it al-
ways floats; and rifes, and falls with the tide, or as land-
waters fill the river; it is near 300 yards long, and is paved
with lone juft as the ftreets are: carriages with the greatefl
burdens go over it with eafe, and men and horfes with fafe-
ty, though there are no rails on either hand. The boats are
very firm, and well moored with ftrong chains; and the
whole well looked to, and conflantly repaired, though now
very old.
D.
EGREE, in geometry, a divifion of a circle, includ-
ing a three hundred and fixtietb part thereof. See
CIRCLE.
Every circle, great and fmall, is fuppofed to be divided into
360 parts, called degrees: the degree is fubdivided into 6o
leffer parts, called minutes: the minute into 6o others, called
feconds: the fecond into 6o thirds, &c.-It follows, that the
degrees, minutes, &c. of greater -circles, are greater than
thofe of lefs. See MINUTE, SECOND, &C.
The fubdivifions of degr s are fraaions, whofe denomina-
tors proceed in a fexagecuple ratio; that is, a firl minute is
=  0, a fecond =      3-A   a third.=    o    &c. But
there denominators being troublefome, their logarithms are
fubftituted in common ufe, as indices thereof.  See LOGA-
RITHM.
Thus, a degree, as being the integer or unite, is denoted by
o, a firif minute or prime by I, a fecond by 2 or ", a third
by 3 or "', &C. Accordingly 3 degrees, 25 minutes, i6
thirds, are wrote, .30. 25', 16". See SEXAGESIMAL.
But though the ancient Egyptians, to whom this divifion is
ufually afcribed, did, by means hereof, free aftronomical
calculations from fradions; fince fexagefimal fraftions may
be handled as integers; and were very happy in the choice
of fuch a number of degrees in the circle, as admitted of
a jul divifion by 2, 3, 4, 5, 6, 8 and 9. Yet Stevinus,
O4ghtred, Wallis, &c. with good reafon, wifh the fexage-
fimal fradions fet afide, and decimals taken in their room.
For in decimals there is no occafion for reducing leffer frac-
tions into greater, or greater into leffer; which is a tedious
article in fexagefimals. Stevinus even holds, that this divi-
fion of the circle which he contends for, obtained in the
wife age, in Seru/o Sapienti. Stevin. Co/mag. Lib. I. Def 6.
See DECIMAL.
The magnitude or quantity of angles is accounted in degrees.
Thus, we fay, an angle of 90 degrees; of 70 degrees, 50 m i-
nutes; of 25 degrees, 15 minutes, 45 feconds. See AN G L E.
Such a Etar is mounted fo many degrees above the hori-
zon, declines fo many degrees from the equator. See AL-
TITUDE.
Such a town is fituate in fo many degrees of longitude and
latitude. See LONGITUDE and LATITUDE.
A fign includes 30 degrees of the ecliptic.  See SIGN.
DEG R E E of latitude, is the fpace of 365I84 Englifh feet in-
cluded between two parallels of latitude. See LATIT U DE.
DE G RE E of longitude, is the fpace between two meridians;
the quantity of which is variable accordingto the latitude.
See LONGITUDE.
Thefe expreflions are borrowed from the ancients, who were
acquainted with a very large exant of earth frQm eaft to
welt,