BHIIH; K. 



535 



' reaching between them, into which they should b<- 

 f\"* "' tied ; and sometimes vaults may lie cmi tructcd be- 

 tween them, and converted to useful purposes. 



At the terminations of the wing walls, there should 

 be newells or pilasters ; and these are made round, 

 square, or octagonal, as is most suitable to the general 

 design. The masonry of the wing \v ills is similar to 

 what has been described for the outside walls of the 

 spandrels. 



Or PARAPETS. 



|jp r :j. The whole work having been brought up to the 

 level of the cordon, or cornice, and that having also 

 been set, the parapets are to be constructed, i'hcy 

 are made from three feet six inches to six feet in 

 height above the footpaths or roadway : four feet 

 four inches is quite sufficient for protection and de- 

 coration, and is not so high as to obstruct the view. 

 Parapets of the best finished bridges, consist of a 

 plinth, dado, and coping. In their large bridges, the 

 French make the thickness of the parapet two feet ; 

 in Britain, the dado or middle member is made only 

 from 10 to 12 inches in thickness, and the plinth so 

 much more as to leave an offset of about an inch on 

 each side. If the plinth has mouldings on the upper 

 edges, the thickness is made somewhat more. The 

 coping is made from six to nine inches in thickness, 

 and has projections on each side. The top is most 

 generally made to slope each way from the middle, 

 sometimes in straight lines, and sometimes circular ; 

 and there are instances of the slope being made in one 

 inclination, from the inside to the outside. Sometimes 

 the edges are plain, and often moulded : when they 

 are plain, a cavetto or small hollow is cut in the pro- 

 jecting part of the bed, to prevent the water, which 

 "falls on the top, from running down the face of the 

 dado. In or near to large cities and large towns, or 

 near to the dwellings of the wealthy, instead of the 

 dado being all made solid, ballusters are introduced ; 

 and these occupy a larger or smaller space, according 

 to the fancy of the designer. Sometimes there are 

 half ballusters on the outside for appearance, the 

 inside being solid. There are situations which re- 

 quire this. The north bridge in Edinburgh being ex- 

 posed to violent gusts of wind, the open ballusters 

 were found inconvenient, and the spaces between were 

 closed along the inside. 



All the stones for the parapets should be of the 

 best quality the neighbourhood affords : they should 

 be worked and set very correctly. The ballusters are 

 frequently turned in a lathe, and have spaces cut in 

 the plinth and coping to receive their top and bot- 

 tom ends : the coping must be secured in the end 

 joints, by dovetails, cramps, or cast iron dowels. The 

 latter mode is the best : the dowels are four inches in 

 length, and about one inch square : they are let into 

 the middle of the end joints as the stones are set ; the 

 rest of the joints, especially the lower side, is made up 

 very closely with lime mortar, or British cement, and 

 a si'inll perpendicular channel is cut in each stone, 

 wluch. whe ji-.in-.'d, communicates from the top to 

 the tlowcll : down this melted lead is poured, which 

 fill* up the space round the dowell, and also the small 



channel ; or British cement may be used initetd of V' 

 lead. 



The outline <! tin- cornice and parapet should be 

 a curve for the wli ,le length ot tin- In;. I/.-, which 

 abutting on each shore, conveys a stiun/ > i.lr 4 u f se- 

 curity, than wiien tin top It a horizontal line ; but 

 the real advantage is the road way being kept con- 

 stantly clean and dry. 



In bridges when the parapets are made solid, and 

 where proper stones can be procured, it it advisable 

 to make each parapet of one row of stones, about 

 three feet six inches in height, and diminishing from 

 12 or 1 1 inches at the bottom, to 8 or 9 inches at the 

 top, which is made convex : each joint should be well 

 secured by iron dowels. 



Where parapets are made of rubble masonry, from 

 18 to 2t inches in thickness is required, to admit of 

 two stones in breadth. These should be carefully 

 bonded together, and coped, either with a course of 

 squared stones dowelled together, or otherwise with 

 stones about nine inches in depth set on edge. These 

 parapets should have their top and coping curved 

 down to the ground at each end ; and be there se- 

 cured by a stone of considerable size, fixed firmly 

 under the surface. 



OF THE ROADWAY. 



In places of great thoroughfare, there are usually 

 footpaths : indeed, for the protection and comfort of 

 foot passengers, who form the greatest proportion of 

 mankind, footpaths ought to be made along every 

 bridge, and also every road. Nothing can be more 

 degrading and unfair, than that those very personi, 

 by whose labours bridges and roads are obtained, 

 should be mixed with, and exposed to be trampled on, 

 by horses, or crushed by wheel carriages. 



When the spandrels have been covered by arches 

 or flat stones, it is only necessary, for the footpaths, 

 to build with rubble stone foundations for the outside 

 curbing. This curbing should be of hard stone, (say 

 granite,) about from 12 to Ij inches in depth ; and 

 from 6 to 9 inches in thickness on the upper edge. 

 Their lengths should be as great as can be convenient- 

 ly procured, and they should be set in lime mortar. 

 The space between the curbing and the parapets, 

 should be paved with hard flag stones, 3 or 't inches- in 

 thickness, well faced and jointed. They should be laid 

 in lime mortar upon a bed of coarse sand, or clean gra- 

 vel. In large bridges, the whole of the footpaths is 

 sometimes covered with granite. The breadth of foot- 

 paths varies from three to more feet: three feet will admit 

 of one person walking with safety, four feet six inches 

 will admit of two, and six feet >( three. The top of 

 the footpath should be from 6 to 10 inches above the 

 bottom of the side channel. Along the outside of 

 the curb stones, the French place borne or fender 

 stones ; but passengers, horses, and carriages, may get 

 entangled and injured by them ; it is therefore pre- 

 ferable to have small paving stones set, forming an 

 inclined plane between the outer edge of the curbing, 

 and the bottom of the side channel: this will efiei- 

 tually prevent carriages from coming upon the foo'. 

 path. 



