BRIDGE. 



ileven fort. To Hrengthcn it liOrir.or.t:illy, it is made wideft 

 at ilic abiitnnciits, from which it coi.tradts towards tlie centre 

 b) fcven otf-fcts, fo tliat the road-way is one foot nine 

 inches «iJcr 3t the cxtrtmilits than at the middle. 



The briJffcs of Wellminllcr and ISlatkfriars, over the 

 liver Thames at London, arc among the fintU lUuctures of 

 the kind in Europe. The former is i.;JO feet long, and 44 

 fctt wide, haunj; a coniinodioiis broad footpath on each 

 fide ff>r pafTenntis. It confilli of tliiitccn large, ai-.d two 

 fmall arches, fuuitciii intermediate piers and two abutments. 

 The length of each abutment is 76 feet ; the opening of 

 cacli of the fniallcr archts is 25 fcit ; the fpan of the hrll 

 of the large arches at each end is i2 feet, of the next j6 feet, 

 aiid fo on increaling by four feet at a time to tlic centre 

 arch, the fpan of which is jC) feet. The two piers of tiie 

 middle arch a>-c i- feet wide, and the others decreafe equally 

 on each hdt, by one foot at a lime, even- pier terminating 

 wHth a falicnt riglit angle againll either llream. The arches 

 are femi-circular, and fpring from about the height of two 

 feet above low water. The breadth of the river in this 

 place is about 1220 feet, and tlie water-way through the 

 bridge amounts to 870 feet. The bridge was liegun in 

 1738, and opened for pafTengers in 1750, at a neat cxpence 

 of 2iS,>Sool. It is conftruftcd of the beft materials, and in 

 .« neat and elegant talle ; but the arches are too fmall in pro- 

 portion to the quantity of mafonry. 



rdackfriars bridge, nearly 0])poiitc to the centre of the city 

 of London, was begun in i7''jo, and completed in ten years 

 and three quarters, at a neat expence of 152,8401. It is an ex- 

 ceedingly light and elegant llrufture ; but, unfortunattly, the 

 materials do not feem to be of the bell kind, as many of the 

 ftones in the piers are decayed. The bridge confiils of nine 

 large, handfome, and nearly elliptical arches ; the central 

 arch is 100 feet wide, and the four arches on each fide, 

 reckoning towards the (liorcs, decreafe gradually, being 98, 

 93, 83, and 70 feet refpettively, leaving a water-way 0^788 

 feet. The whole length from wharf to wharf is 995 feet, 

 the breadth of the carriage-way i8 feet, and that of the 

 raifed foot-wav on each fide feven feet. The upper furface of 

 the bridge is a portion of a very large circle, which forms 

 an clerfant figure, and admits of convenient pafTage over it. 

 On each pier there is a recefs or balcony, with two Ionic 

 columns and pilafters, which Hand on a circular projeftioii 

 of the pier above high water mark. The bridge is rounded 

 ofT at each extremity to the right and left, in the form of a 

 quadrant of a circle, rendering the accefs commodious and 

 agreeable. This edifice mull be regarded as a fine fpecimcn 

 ot Mr. Mylne's ingenuity and jwlgment, though the method 

 of c(m(lruclion has neitrr been made pubhc. 



Uefides the bridges already mentioned, there are many 



other neat and elegant flrutlures in diffirtnt parts of Great 



]?ritaia and Ireland. The bridge over the Tees at Vv'infton 



in Yorkfhire, was dtiigned by fir Thomas Robinfon, 



■and built by John Johnfim, a common mafon at Walfing- 



4iam, in the year i 76:. It confiils of a finjjie arch loS feet 



-9 inches fpan ; is built of rubble-ftone ; and coll only /Jool. 



An elegant flonc bridge has lately been built over the 



Tweed at Kelfo, upon the plans and imder the direftion of 



Mr. John Rennie. This has five elliptical arches of 72 feet 



fpan each ; is quite level at top. It has two Doric pilafters, 



which Hand on a circular projection of the pier, with a fimple 



block cornice. The coll of this bridge was about 13,0001. 



exclufivc of the roads at each end, which coll about 3CO0I. 



more, in all i6,oocl. 



The bridge over the Peafe, or rather Pcnths, on the road 

 from Dunbar to Ik-rwick upon Tv.eed, is rathtr an luicom- 

 mon ftrudure. This bridge croll'es a deep ravine called the 



Peaihs. It confifts of four femi-circular arches. That at 

 the call fide of the ravine is 54 feet fpan ; the fecond 5; 

 feet; the third 52 feet, and the further or weftern arch 48 

 feet. The height of the bridge, from the bottom of the 

 ravine to the furface of the road, is 124 feet. The fituation 

 is beautiful, and has a moft romantic appearance. It was 

 dcfigned and built by the late Mr, David Henderfon, 

 architcft in Edinburgh, and does him confiderable credit. 



The aqujcdudl bridge, conltnifted by Mr. Rennie on the 

 river Lunc at Lancaller, is one of the moll magnificent work 5 

 of the kind which has been erefted for the purpofes of navi- 

 gation. At the place where it is built, the water is deep and 

 the bottom bad. it confiils of 5 arches of 70 feet fpan each, 

 and about .39 feet above the furface of the water. It has a 

 handfome cornice, and every part of it is finilhed in the befc 

 manner. The foundations are laid at the depth of 20 feet 

 under the furface of the water, ard ftand on a flooring of 

 timber, fupportedbypiles. The foundation alone coft i5,oool. 

 The fuperllrutlurc cofl above twice that fum, although the 

 ftone was found within about a mile and a half of the place 

 where the aqureducl was built. Barges of 60 tons burthen 

 navigate the canal. The total height from the furface of the 

 river to the furface of the canal is 51 feet. 



It may be obfcrved in this place, that the Romans always, 

 without any exception that we are acquainted with, made 

 their arches either of a ftmiclrcle, or of a Icfier fegment of 

 a circle. The vouflbirs were generally included between two 

 concentric curves, on which account thefe are called extra- 

 doffed arches. The earlier Italian architedls followed the 

 example of the Romans in the forms of their arches, which 

 are either femicircular, or of a fmaller fegment, called by 

 them area intiero, and arcofcemo, from which term our woik- 

 men have taken that oi Jleme arch. Elliptical arches are 

 very much ufed by the engineers of Erance, moft of the 

 bridges in that country being in this manner. The French 

 diftinguifti their arches into three kinds, I'arc plein-cemtrc, 

 I'arc fiirhmijje, and I'arc furlo'ijfi ; the firft is a femi-circlc, 

 the fecond higher, and the third lower than a femi-circle, 

 being formed by the greater or fmaller axis of an cllipfis ; in 

 praftice, however, thefe are generally compofed of feveral 

 arcs of circles of different diameter, as in this cafe the joints 

 are more eafily traced. The arcs fuvbaiflcs are alfo called 

 atife de panicr. The arc bomhc is an aic furbaiflc, formed by 

 a fegment of a circle. 



The ancients always laid their wrought ftones without 

 mortar between the joints, frequently ufing iron cramps to 

 connett them more firmly together. Their large arches, and 

 thofe v.hieh had to bear very great weights, were compofed 

 of feveral ranks of vouftoirs extradofted, and breaking joint, 

 as is feen in the great cloaca of Rome, and in feveral bridges 

 and aquredufts. Modern architedls, however, generally ufe 

 only one rank of vouftoirs, each of which is terminated at 

 top by a horizontal joint, and laterally by a perpendicular 

 joint, for the purpofe of ranging better with the courfes of 

 the haunches and fpandrels. 



The decoration of bridges ought to be fimple and large, 

 their beauty confiftmg chiefly in the proportion of the voids 

 and folids, the contour of the arches, and apparent ftrength 

 and folidity, together with boldnefs of conllroftion. How- 

 ever, many modern architects have carried finiplicity to ex- 

 cefs, particularly in Paris, where the arches of all the bridges 

 are plain, and without any member of architecture. A 

 happy introduflion of ruilic work of various forms and 

 fizes breaks the monotony of the Inrge mafl'es, and enriches 

 the edifice. This method was often employed by the an- 

 cients, and we never Hud that they nc^lifted to ornament 

 the arches of their bridges v ith archivolts more or lefs rich. 

 I Pailadio, 



1 



