180 RENNIE'S BRIDGES. PART VII. 



two three-quarter Doric column pilasters, after the design 

 of the temple of Segesta in Sicily. These pilasters are 

 5 feet 84 inches diameter at the base, and 4 feet 4 inches 

 at the under side of the capital, forming recesses in the 

 roadway 17 feet wide and 5 feet deep. The depth of 

 the arch-stones at the crown is 4 feet 6 inches, and they 

 increase regularly to 10 feet at the haunches. Between 

 each pair of arches, at the level of 19 feet above the 

 springing, there is an inverted arch, the stones of which 



SECTION OF WATERLOO BRIDGE. 



are 4 feet 6 inches deep at the crown, arid decrease 

 regularly on each side as they unite and abut against the 

 extrados or backs of the voussoirs of the main haunches. 

 The abutments are 40 feet in thickness at the base, and 

 decrease to 30 feet at the springing. The cope of the 

 arches and piers is surmounted by a Grecian Doric 

 block-cornice and entablature, upon which is placed a 

 balustrade parapet 5 feet high. The total width of the 

 bridge from outside to outside of the parapets is 45 feet. 

 The footpaths on each side are 7 feet wide, and the 

 roadway for carriages 28 feet. There are four sets of 

 landing-stairs two to each abutment ; and the arrange- 

 ment of this part of the work has been much admired, 

 on account of its convenience for public uses as well as 

 its architectural elegance. 



In the construction of this bridge, there are four fea- 

 tures of distinctive importance to be noted : 1 st. The 

 employment of coffer-dams in founding piers in a great 

 tidal river an altogether new use of that engineering 

 expedient, though now become customary. 2nd. The 

 ingenious method employed for constructing, floating, 

 and fixing the centres ; since followed by other engineers 

 in works of like magnitude. 3rd. The introduction and 

 working of granite stone to an extent before unknown, 



