16 Design for a Bridge [JaN, 



of stone, or framework of timber or cast-iron. To the tops of 

 these piles the rods C and D might be fastened, each preserving 

 the same degree of inclination under the road which it has over 

 it. The power of the rods to draw these piles diminishes in the 

 same ratio as the angle of incidence, viz. the acute angle which 

 the rods form with the pavement, or heads of the piles ; and 

 will be indicated by the diagonals of parallelograms constructed 

 on the same principle as those in Fig. 11, at 1, 2, 3, &c. 



For the sake of simplicity, and economy in excavation, the 

 rods are conjoined in pairs under the road, each pair being 

 passed through a strong ring, or link, as at Y, Fig. 3, and after- 

 wards earned down together to the rock. 



If the rock is compact at the surface, then, by increasing the 

 dimensions of the rods, a smaller number than that shown in the 

 elevation will be sufficient to counteract every possible strain to 

 which they will be liable. 



In the case of a bridge on this principle consisting of a series 

 of equimensurate openings, of course no such rods would be 

 requisite any where but at its termination or abutments. 



D, extremities of those rods which form the basis of the road- 

 way, and also some of the suspending rods, intlected over the 

 fulcrum or wall of masonry, S, and made fast to the rock. If 

 there is a command of the ground for 100 or 200 yards at each 

 end of the bridge, in the direction of its length, even these small 

 fidcrums are unnecessary, as observed above. (See C.) 



E, roadway, the basis of which is composed of iron rods, as 

 arranged in Fig. 8, to which is bolted the wrought-iron frame- 

 work, exhibited in Fig. 7, the covering being convex cast-iron 

 plates screwed together (but not to the framework), as at W, 

 Fig. 7. The whole is then covered with clay, chalk, and gravel, 

 as in the section Fig. 6, with a protecting rail for the foot-paths, 

 as at X, X, Figs. 5 and 6, and an outside cast-iron parapet, as 

 at Fig. 4. 



F, stays to the columns of the fulcrums. 



G, H, I, struts to these stays, composed of flanched plates of 

 cast-iron. 



K, L, M, N, O, P, horizontal plates flanched, and with the 

 flanch arched towards its juncture with the stays, so as to abut 

 on them, and thus to serve as binders ; that is, both as strut* 

 and ties. 



Q, foundation of the pier on the rock. 



R, excavation to the rock, in order to admit of fixing the rods 

 C, C, thereto, by Lewis's or otherwise, as well as laying the 

 foundation of S. 



S, abutment or fulcrum of masonry at each shore or termina- 

 tion of the bridge. 



T, basement of the road, composed of rods connected, as 

 shown on a larger scale in Fig. 8. 



U, wrought-iron framework, placed on and fixed to the 

 6 



