ARC 
whole made more commodiousthe two middle arches 
were then thrown into one, by removing the pier from be¬ 
tween them; the whole repairs amounting to above 8o,occl. 
There are (till more bridges in England built in the old 
manner of London-bridge'j as the bridge at Rochefter, 
and fome others ; alfo the late bridge at Newcadle-upon- 
Tyne, which was broken down by a great Hood in tire 
year 1771, for want of a fufficient quantity of water-way 
through the arches. The longed bridge in England is 
that over the Trent at Burton, built in the twelfth cen¬ 
tury, of fquared free-done, and is drong and lofty; it 
contains thirty-four arches, and the whole length is 1545 
feet. But this falls far fliort of the wooden bridge over 
the Dravc, which according to Dr. Brown is at lead five 
miles long. But one of the mod lingular bridges in Eu¬ 
rope is that built over the Taaf in Glamorgandiire, by 
William Edward, a poor country mafon, in the year 1756. 
This remarkable bridge eonlids of only one llupendous 
arch, which, though only eight feet broad, and thirty- 
live feet high, is no let's than 140 fpan, being part of a 
circle of 175 feet diameter. There is alio a remarkable 
bridge of one arch, built at Colebrook Dale in 1779, of 
cad-iron : anti another dill larger, of the fame metal, over 
The river Wear, at Sunderland, the arch being of 240 
lcet fpan. 
Of modern bridges, perhaps, the two fined in Europe 
are, the Wedminder and Biackfriars bridges over the ri¬ 
ver Thames at London. The former is 1220 feet long, 
and forty-fc ir feet wide, having a commodious broad foot¬ 
path on each fide for palfengers. It confids of thirteen 
large and two fmall arches, all femicircular, with four¬ 
teen intermediate piers. The arches all fpring from about 
two feet above low-water mark; the middle arch is le- 
venty-fix feet wide, and the others on each fide decreafe 
always by four feet at a time. The two middle piers are 
each feventeen feet thick at the fpringing of the arches ; 
and the others decreafe equally on each dde by one foot at 
a time; every pier terminating with a falient right angle 
againd either dream. This bridge is built of the bed 
materials, and in a neat and elegant tade, but the arches 
are too fmall for the quantity of mafonry contained in it. 
This bridge was begun in 1738, and opened in 1750; and 
the whole fum of money granted and paid for the erection 
of this bridge, with the purchafe of houfes to take down, 
and widening the avenues, &c. amounted 389,5001. 
Blaekfriars-bridge, nearly oppodte the centre of the 
city of London, w as begun in 1760, and completed in ten 
years and three-quarters; and is an exceeding light and 
elegant drudture; but the materials unfortunately do not 
feetn to be of the bed, as many of the arch-dones are de¬ 
caying. It coitfids of nine large, elegant, elliptical, arch¬ 
es ; the centre-arch being 100 feet wide, and thofeon each 
fide decreasing in a regular gradation, to the (mailed, at 
each extremity, which is feventy feet wide. The breadth 
of the bridge is forty-two feet, and the length from wharf 
to wharf 995. The upper furface is a portion of a very 
large circle, which forms an elegant figure, and is of con¬ 
venient padage over it. The whole expence was 150,8401. 
and Mr. Milne was the architefi. 
There are various forts of bridges, of done, wood, or 
iron, of boats or floats, pendant or hanging bridges, draw¬ 
bridges, flying bridges, &c. &c. for which fee the article 
Bridge. 
Of QJJ AYS or HARBOURS. 
1 he fird thing to be eonddered in forming a quay or 
harbour, is the choodng a dtuation favourable by nature 
to the end propofed ; fuch as a large creek or bafon, where 
(hips can lie fafe in dormy weather, and where there is 
likewife a (ufficient depth of water for large diips to enter 
and remain without touching the ground. The depths of 
water where the piers are to be built mud be taken at every 
ten, fifteen, or twenty, feet didance, and marked upon 
piles driven here and there, in order that the workmen 
may be directed in laying the foundation. It muft be next 
ARC 127 
eonddered what kind of materials are to be ttfed, whether 
done, brick, or wood. If dones are to be had at a mode¬ 
rate price, they ihould be preferred, becaufe the work 
vv ill be much (tronger, and w ant fewer repairs : but, when 
dones are too expendve, the foundation may be made of 
done as high as low-water mark, and the ted finifhed with 
brick. It tHis fnould dill be too expendve, w'ood mud: 
be ufed ; and piles driven clofe, and faftened together by 
crols-bars, covered with drong oaken planks, fo as to form 
a kind of cotter, which may be filled with (tones, chalk, 
Hi ingles, &c. 
1 he manner of laying the foundation in different depths 
of water, and in various foils, requires different methods 
to be followed. When the water is very deep, a coffer 
muft be made with dove-tailed piles of about thirty yards 
long, and as wide as the thicknefs of the foundation isto 
be: then the ground is dug and levelled, and the wall;is 
built with the bell mortar. As foon as tlie mortar is to¬ 
lerably dry, the piles at the end of the wall are drawn out, 
the fide-rovvs are continued to about thirty yards farther, 
and the end inclofed ; then the foundation is cleared, and 
the dones laid as ufual. But it mud be obferved, that the 
end of the foundation is left rough, in order that the part 
next to it may incorporate with it in a proper manner ; but 
if it is not very dry, it will incline that way of itfelf, and 
bind with the mortar that is thrown next into it: this me¬ 
thod is continued til! the whole pier is entirely finifhed. 
Anotlicr method is to build in coffers, much after the 
fame manner as was done in building the piers of Wedmin- 
der-bridge; but as in this cate the ends of the coders are 
left in the wall, and prevent their joining fo well as to be 
water-tight, the water may penetrate through, and render 
the work infecure. The proper thicknefs of piers can on¬ 
ly be determined by experience. Some architefts fuppofe, 
that if the thicknefs ot a pier be equal to the depth of 
the water, it is fufficient; but for a greater fecurity they 
allow tvvo, three, or four, feet more. This might proba¬ 
bly do, if the pier were built with folid dones cramped to¬ 
gether; but, as its infide is filled up with (hingles, chalk, 
or other loofe materials, their rule is not to be depended 
on ; befides, it makes the fpace above too narrow for la¬ 
ding and unlading fhips, unlefs in a great depth of water: 
fo that it does not appear that their method can be fol¬ 
lowed, except in a very few cafes where the water has no 
condderabie motion. 
The wall mud be built with terrace-mortar from the 
bottom to the height of low-water mark, and the red fi¬ 
nifhed with cinder or tile-dud mortar, which has been found 
diffidently good in thofe places where the wall is wet and 
dry alternately. The upper part of the pier (hould be 
paved with flat hewn dones laid in drong mortar, in order 
to prevent any water from penetrating into it. Iron rings 
ought alfo to be fixed here and there at proper didances, to 
faden the fhips,and prevent them from driking againd the 
pier. Wooden tenders or piles diould be driven at the in¬ 
fide clofe to the wall, and cramped to it with iron, to pre¬ 
vent the (flips from touching them, and doing mifehief by 
their continual motion. Where the fea breaks againd the 
piers with great violence, breakers (hould be made at pro¬ 
per didances; namely, two rows of piles driven nearly at 
right angles to the piers for the length of about twelve or 
fifteen feet, and at about eight or ten feet didance from 
each other; and then another to join the two former: 
thefe piles being covered with planks, and the infide being 
filled with fhingie and rubble dones, the top is then paved 
with dones of about a foot in length, fet longwifeto pre¬ 
vent the waves from tearing them up. This precaution is 
abfolutely necedary where the tide flows in very rapidly. 
A RC HI'T HOI.(JS, f. from app^, the fird, 
and SoA^, a chamber.] The fudatorium, or principal 
room of the ancient baths. 
ARCHl'TIS, the name of Venus, who was wordiipped 
on mount Libanus. 
AR'CHlTRAVE,yi in architefture, that part of a co¬ 
lumn which lies immediately upon the capital, being the 
1 lowed 
