314 Ticecd Chain Bridge. — KegeiiCs Canal. 



The method adopted in the erection of this bridge holds out 

 great promise of ecoimmv in future bridge-building. No exca- 

 vation required ; no coffer dams ; but merely the iron columns 

 driven as far into the earth as they could be by a pile engine : 

 thev were then made the fulcrum of a lever loaded with three 

 times the calculated weight of the bridge. The bridge is also so 

 constructed as to require no spandrils — thus leaving the same alti- 

 tude for the passage of vessels under everv part of the span. 



The principal strength and stability of this bridge is obtained 

 by elliptical arcs and chords, kept so flat that the purposes of 

 the truss girder are fullv obtained, but with siiperior elegance 

 and greater strength, and may be extended to an indefinite length. 

 —Two of those cross the river, their extreme ends resting on the 

 iron pillars driven in the river banlis, and not projecting higher 

 than the hand rail of tJie balustrades — with an extended chord 

 from the two points of the basement, holding them together, and 

 preventing their extending by pressure ; to which elliptical arc- 

 piece are attached or hung chords of suspension for supporting 

 the bridge- flooring — these chords of suspension being flat, form 

 stiles between pannels of tasteful Gothic work ; the whole form- 

 ing balustrades on each side the bridge. It being on the prin- 

 ciples of tenacity, the chief part of the iron acts longitudinally by 

 tension. There are grooves in the top of those iron columns, on 

 which the whole bridge has room to contract or expand, so ne- 

 cessary in this climate from the various changes of the atmo- 

 sphere from heat and cold, as the other previous iron bridges 

 have suffered materially from the want of this precaution, and 

 evidence has been given before the Parliament, thac the South- 

 wark bridge rises from 2 to 2~ inches in the middle of the day, 

 and settles again in the evening. By those iron columns in the 

 river, instead of piers or buttresses, if they resist the floating ice, 

 of which from their strength and stability there can be no doubt, 

 Mr. Dodd, the engineer, has certainly introduced an economical 

 plan in bridge-building, as in this there is no occasion for bat- 

 tred'eaux, coffer-dams, &c. ; a saving most desirable in the ex- 

 pensive work of bridge-building — particularly so, as they are exe- 

 cuted with such facility, and without the expense of centering, 

 and upon this principle tan be built to any order, instead of the 

 fiUagree patterns hitherto adopted. 



CHAIN BRIDGE. 



Capt. S. Brown, R.N., has completed the chain bridge over 

 the Tweed. The breadth of the river is 437 feet ; and the bridge 

 crosses the whole in one stretch, without any middle support. 



THE REGENT S CANAL. 



The magnitude of London, and thevastness of its population, 



might 



