CHAP. XIX. 



PROPOSED BRIDGE. 



421 



throughout as not in any way to interfere with the 

 navigation of the Strait. From an early period, Mr. 

 Stephenson had fixed upon the spot where the Britannia 

 Rock occurs, nearly in the middle of the channel, as the 

 most eligible point for 

 crossing ; the water- 

 width from shore to shore 

 at high water there being 

 about 1100 feet. 



The engineer's first 

 idea was to construct the 

 bridge of two cast iron 

 arches, each of 350 feet 

 span. There was no 

 novelty in this idea ; for, 

 as early as the year 1801, 

 Mr. Rennie prepared a 

 design of a cast-iron- 

 bridge across the Strait 

 at the Swilly rocks, the 

 great centre arch of 

 which was to be 450 feet 

 span ; and at a later 

 period, in 1810, Telford 

 submitted a design of a 

 similar bridge at Inys-y- 

 Moch, with a single cast-iron arch of 500 feet. But 

 the same objections which led to the rejection of Ren- 

 nie' s and Telford's designs, proved fatal to Robert 

 Stephenson' s, and his iron-arched railway bridge was 

 rejected by the Admiralty. The navigation of the 

 Strait was under no circumstances to be interfered 

 with ; and even the erection of scaffolding from below, 

 to support the bridge during construction, was not to 

 be permitted. The idea of a suspension bridge was 

 dismissed as inapplicable; a degree of rigidity and 

 strength, greater than could be secured by any bridge 



