1 90 Mr. White's Design for the New hondoii Bridge, 



an ornamental figure is introduced at each pier on a base 

 elevated above the high-water mark. 



Simple segments of circles are used for the form of the 

 arches ; first, on account of the imperfection which appears in 

 the outline of elliptical arches when viewed from below ; and 

 secondly, because the same centering may be used in their 

 erection. 



Elliptical openings are shown over each pier, not only for 

 the purpose of saving materials, but weight, and in order to 

 give lightness and elegance of effect. 



The faces of the bridges are proposed to be of tooled stone, 

 without chamfering or any I'oughness, which retains the dust 

 or smoke. 



With regard to the stone itself, the cementitious or adhesive 

 bridge may be of best Kentish rag, best Dartmoor [granite], 

 best Aberdeen [granite], selected Portland stone or brick 

 mixed, all in small sizes. The only essential point is, that 

 there should be an uniform external facing of best rag or gra- 

 nite, well united with the internal materials. The stones of the 

 bonded bridge should be the shapes described by the draw- 

 ings, and of dimensions to lie in equal layers or beds. 



As to the pavements, the carriage way should be made with 

 best granite stones of the proportions following; viz. 10 to 14 

 inches, by 4^ to 5 inches on the face, and 1 2 inches deep ; the 

 foot pavements laid with six-inch granite slabs. 



The centering is suggested to be of cast-iron ribs supported 

 by piles until the arches with part of the superstructure be 

 completed, these ribs to be removed as the work advances. 



There now appears so much science in forming caissons 

 and coffre-dams, that it only remains to notice that the double 

 coffre-dam appears to the author essential in the situation 

 pointed out, on account of the rapidity of the current ; the 

 interval between the piling to be filled with the toughest clay 

 intermixed with gravel, and well rammed. As to the ex- 

 pense, the length of the piles must determine the amount in a 

 great degree, and therefore it would be imprudent to offer 

 any calculation thereon, without an opportunity of making 

 trial of the bed of the river. 



As to the Expe7ise of the Cqffre-dam. — The expense of the 

 coffre-dams cannot be estimated without drawing several proof 

 piles; the timber and workmanship can hardly be less than 

 10/. per load for best Dantzic, Memel, or Riga timber, and 

 11. 10s. for American yellow fir, which is conceived to be quite 

 good enough for the purpose. 

 As to theExpense of Erecting theBridge, including the Paving. 



— The 



