a Hanging Iron Bridge across the Menai Strait. 15 



tent of four or five inches ; but both agree, that the changes 

 arising from the temperature will not derange the bridge. 



6. Repairs. — It appears from the evidence, that the cables, 

 suspending rods, and roadways, will be so constructed and united 

 together, that each part may be taken out and repaired sepa- 

 rately. 



Your Committee feel great satisfaction in having it in their 

 power to say, that Mr. Telford has completely convinced them 

 of the practicability of his plan. The numerous instances which 

 he has already given to the public of his talents as a civil en- 

 gineer, fully prove that the House may place great confidence in 

 his opinion. But when his opinion is supported by Mr. Rennie 

 and other engineers, the case of the practicability of this under- 

 taking appears to be as completely made out as it is in the na- 

 ture of things to allow of its being established. 



When it is remembered, that the first estimate prepared for 

 Lord Colchester (when Chief Secretary for Ireland) for building 

 a cast iron arched bridge across the Menai amounted to 268,500/. 

 your Committee are of opinion, that the public stand greatly in- 

 debted to the industry and talents of Mr. Telford, for having 

 contrived a plan on so secure a principle, for executing this work 

 for the sum of 70,000/. 



April 29th, 1819. 



The following particulars are copied from the Appendix to the 

 foregoing Report. 



Mr. Telford in answer to a question by the Committee gave 

 in the following statement in writing : 



** In order to avoid interrupting the navigation, it is evident 

 that a horizontal roadway is most advisable ; and to obtain this, 

 a bridge, upon the principle of suspension, seems unavoidable ; 

 it is therefore adopted at the height of 100 feet above the high 

 water of spring tides. The distance between the points of sus- 

 pension is 5G0 feet, and the versed sine is 37 feet or about l-15th 

 of the chord line. The breadth of the bridge will be about 30 

 feet, having two carriage-ways of 12 feet each, and a footpath of 

 four feet between them. This affords four points of suspension 

 in the breadth of the bridge. The whole roadways are to be 

 suspended from the main cables by means of perpendicular rods, 

 and are therefore to be considered as mere weight. The iron- 

 work of the cables and timber of the roadways are to be con- 

 structed so that they may be taken out and replaced separately. 



" Ry calculation I find that the weight to be suspended is 

 342 tons : by niunerous experiments which I have made to ascer- 

 tain the strength of malleable iron, it apjjears, that witli a chord 

 line of 5G0 feet, and a versed sine of 37 (or a curvatureof l-15th), 

 a bar of good iron, one inch square, will, besides its own weight, 



carry 



