446 TELFORD'S PROPOSED RUNCORN BRIDGE. PART VIII. 



this method of constructing centres as applicable to stone 

 as well as to iron arches ; and indeed it is applicable, as 

 Mr. Brunei held, to the building of the arch itself. 1 Mr. 

 Telford anticipated that, if the method recommended by 

 him were successfully adopted on the large scale proposed 

 at Menai, all difficulties with regard to carrying bridges 

 over deep ravines would be done away with, and a 

 new era in bridge-building begun. For this and other 

 reasons but chiefly because of the much greater dura- 

 bility of a cast iron bridge compared with the suspension 

 bridge afterwards adopted it is matter of regret that 

 he was not permitted to carry out this novel and grand 

 design. It was, however, again objected by mariners 

 that the bridge would seriously affect, if not destroy, the 

 navigation of the Strait ; and this plan, like Mr. Eennie's, 

 was eventually rejected. 



Several years passed, and during the interval Mr. 

 Telford was consulted as to the construction of a bridge 

 over Runcorn Gap on the Mersey, above Liverpool. As 

 the river was there about twelve hundred feet wide, and 

 much used for purposes of navigation, a bridge of the 

 ordinary construction was found inapplicable. But as 

 he was required to furnish a plan of the most suitable 

 structure, he proceeded to consider how the difficulties 



1 In an article in the 'Edinburgh 

 Review,' No. cxli., from the pen of 

 Sir David Brewster, the writer ob- 

 serves : " Mr. Telford's principle of 

 suspending and laying down from 

 above the centering of stone and iron 

 bridges is, we think, a much more I 



pieces of fifty feet each; and by in- 

 creasing the number of suspending 

 chains, these separate pieces or vous- 

 soirs having been previously joined 

 together, either temporarily or perma- 

 nently, by cement or by clamps, 

 might be laid into their place, and 



fertile one than even he himself sup- | kept there by a single chain till the 

 posed. With modifications, by no I road was completed. The voussoirs, 



means considerable, and certainly 

 practicable, it appears to us that the 

 voussoirs or arch-stones might them- 

 selves be laid down from above, and 

 suspended by an appropriate mechan- 

 ism till the keystone was inserted. 

 If we suppose the centering in Mr. 

 Telford's plan to be of iron, this cen- 

 tering itself becomes an iron bridge, 

 each rib of which is composed of ten 



when united, might be suspended 

 from a general chain across the arch- 

 w T ay, and a platform could be added 

 to facilitate the operations." This is 

 as nearly as possible the plan after- 

 wards revived by Mr. Brunei, and 

 for the originality of which, we be- 

 lieve, he has generally the credit, 

 though it clearly belongs to Telford. 



