BRIDGE. 



Palladio, in all liis ckfigns of bridges, has never omitted this 

 fimpleft and belt decoration of arches. Cornicts and bnl- 

 hiftrades alfo are both iif'rful and ornamental in thefe 

 ftrudiures. 



Generally fpeaking, large arches are more expenfive than 

 fmaller. In a bridge lately dcfigned over a river, wherein 

 the foundations uvrc vtry dillieuk to conllruft, one delign 

 with three arches of 1 16 feet each, was eiliiiiated at 1^,174!. 

 and another of live arches of the fame kind was clHniated 

 at 12,04.1!., which was contraClcd for and built tor tlie 

 above fum. 



IFooil.^ri bruises now demand our attention. The fimpleft 

 cafe of th.efe edifices is ihat in which the road-way ii> laid 

 over beams placed horizontally, and liipportcd at each end 

 by piers or polls. This method, however, is deficient in 

 ftrength and width of opening : it is therefore ntceffary, in 

 all works of any magnitude, to apply the principles of 

 trulTnig, as ufcd in roofs and of arches. Wooden bridges 

 of this kind are lliff frames of carpentry, in which, by a 

 proper difpofition, beams are put, fo as to fland in place of 

 folid bodies, as large as the fpaces wliich the beams enclofe ; 

 and thus, two or three or more of thefe are fet in abutment 

 with each other, like mighty arch flones. 



Palladlo has given fever>d very elegant defigns of wooden 

 bridges, which he thus d-fcrihes. The bridge of the 

 Cifmone. The Cilmone is a river, which, falling from the 

 mountains that divide Italy from Germany, runs into the 

 Brenta a little above Bafiano. And, becaufe it is very ra- 

 pid, and great quantities of timber are fent down it by the 

 mountaineers, it was refolved to make a bridge there, with- 

 out fixing any polls in the water, which were hable to be 

 carried away by the violence of the current, and the Ihock 

 of the ilones and trees that contiimally came down. The 

 invention of this bridge, (fays Palladio,) is, in my opinion, 

 very worthy of attention, as it may ferve on all occafions 

 where thefe difficulties may occur, and becaufe that bridges 

 thus made are flrong, beautiful, and commodious ; (Irong, 

 becaufe all their parts mutually fupport each other ; beauti- 

 ful, becaufe the texture of the timbers is very agreeable ; 

 and commodious, being even, and in the fame hne with the 

 remaining part of the Itreet. Tb.e river where this bridge 

 was erefled is ico feet wide ; this width is divide'd into fix 

 equal parts ; and at the end of each part, excepting at the 

 banks, which are ftrengthencd with pilaflcrs of llone, the 

 beams are placed, that form the breadth of the biidge, 

 upon which, a little fpace being h f t at their ends, were 

 placed other beams lengthways, which form the fides. Over 

 thefe, directly upon the firll, llie coloiielli (king-pofls) 

 were difpofed on each fide ; thefe king-pofls are connefted 

 to the beams which form the breadth of the biidge by 

 means of irons paiFing through the projediing ends of the 

 bcanis, and bolted and pinned through both. See /V. i. 

 P/rt/^ XXXII. ol ArcJr.uaure. 



Palladio proceeds to defcribe three other methods of con- 

 flrucling wooden bridges without polls in the water, like 

 the bridge over the Cilmone. The bridges after the firll 

 method are to be made in this manner: the banks being 

 ftrengthened by pilallers as neccffuy fhall require, one of 

 the beams forming the breadth of the bridge is to be placed 

 at fame diftance from it, then the firll llrut is to be placed 

 with one end upon the pier, and llie other end abutting 

 agalnll the firll queen-poll, which is to be connefted v.'ith 

 the beams by irons. Then tlie fecosd beam for the breadth 

 is to be placed at a diftance equal to the fpace betv.'een the 

 flril beam and the pier, vvhicli is to be Supported in hke 

 manner with a ft rut and quecn-poil, and thus proceeding 

 as far as is required, obfcrving to have a kiiig-poil in the 



middle of t!ie length in which the f'.ruts meet both ways 

 and with collar beams between all the polls which lliffeii 

 and fupport the wliole coiillrutlion. Bridges after this 

 manner are to be wider at the extremities, and contraft to- 

 wards the middle. Kec/r. 2. Phite XXXTI. oi Architetiure. 

 The invention of the following biidge has tiie U[)per part 

 which fuppoits the weight in the form of a polygon, In- 

 fcribed in a flat fegment of a circle ; the beams forming the 

 breadth of the roa<i-way are upheld by king-polls and irons, 

 and the whole lliffened and fuoported by brace.'! croliing one 

 another between tlie king-polls, titruts at each end, reach- 

 ing from the piers to the firll beams, are alio added to (liortea 

 the bearing, and increale the llrength of the fabric. See 

 fig. I. P/j/c. XXXIII. o^ Archiuihirc. 



The third dcfign may be made with a greater or fmallcr 

 arcli than Is here repreft nted. The height of the bridge, 

 in which are plaeed the braces between the king-polls, or ra- 

 ther radii, is to be an elevc;:th part of the fpan. (See/V. 2. 

 Plate XXXIII. 0<l Archih-Hure. 



Mr. Coxe, in the firll volume of his Travels, has fllghdy 

 defcnbed a very fi;'gu!ar bridge at Wiltlngen, in Sv.iHerland, 

 the conilrufliou of which is quite fimple. The loan is 230 

 feet, and it rifes cnly r;. The Iketch (Jig. 3- PI. XXXIII.) 

 will make it fuFficlently intelligible. ADC is one of two 

 great arches approaching to a Catenarian fhapc, built up of 

 7 courfes of folid logs of oak, in lengths of tj or 14 feet, 

 and 16 inches or niore in thicknefs. Thefe arc all picked of 

 a natural lliape, fuited to the intended curve ; fo that the 

 wood is nowhere cut acrofs the grain to trim it into fliape. 

 Thefe logs are laid above each other, fo that their abutting 

 joints are alternate, like thofe of a brick wall ; or, in the 

 language of the workmen, they h real joint. It is indeed a 

 wooden wall, fimply built up by laying the pieces upon each 

 other, taking care to make the abutting joints as clofe as 

 poffible. They are not fallened together by pins or bolts, 

 but held together by iron flraps, which furround them at 

 the diftance of five feet from each other, where they arc 

 faftcned by bolts and keys. Thefe two arches being erecled, 

 and well butted agalnll the rock on each fide, were freed 

 from their fupports, and allowed to fettle. They are fo placed 

 that the intended road abc Interfefts them about the middle 

 of their height. The roadway is fupported by crofs joills, 

 which reft on a long horizontal fuinmerbeam ; and this is 

 connefted with the arches on each fide by uprights bolted 

 into them. The whole is covered with a rouf, which pro- 

 jeds over the arches on each fide, to defend them from tlie 

 weather. Three of the fpaces between ihefe uprlghu h;f\'e 

 ftruts, or braces, which give the upper work a fort of truf- 

 fing in that pait. This bridge is of a llrength mncli more 

 than adequate to fupport any load that can be laid upon it ; 

 though It IS manifelt, by the attempt to trufs the ends, that 

 it was the contrivance of a pcrfon ignorant of principle. It 

 was the work of one Ulrich Grubenhamm, of Tuff"en, in the 

 canton of Appenztl, a carpenter without education, but 

 celebrated for leveral works of the fame kind. 



At Schalihaufen, in Swiffetland, where the RMne flows 

 with great rapuhty, feveial llonc bridges had been deilrovedj 

 when, in 1754, Grubenhamm offered to throw a wooden 

 bridge of a lingle arch acrofs the river, which is nearly 590 

 feet wide. The magillrates, however, required that it fhould 

 confill of two arches, and that he ftiould, for that purpofe, 

 employ the middle pier of the lall ftone bridge, which would 

 divide tl'.e new one into two unequal arches of 172 and x^2 

 feet fpau. The carpenter did lo ; but contiiveti io leave it 

 a matter of doubt, whether the bridge is at all fupported by 

 the middle pier. It was crefted on a plan nearly iimilar to 

 the Witttiigen bridge, at the expeiice of about 8oocl. Her- 



li;ig. 



