20 ANNUAL OF SCIENTIFIC DISCOVERY. 



bolted together. These chains being each 145 feet long, weigh no 

 less than 100 tons. The press being put in operation, in about thirty 

 minutes it raises the tube 6 feet, and here it stops till the masonry 

 can be built up under the tube, when it takes another "hitch" of the 

 same length. It was during one of these " hitches," that one of 

 the presses, for there must of course be one for each end of the tube, 

 broke, owing to some defect, and the tube fell seven inches to the 

 masonry below ; but it was not at all injured, though several of the 

 workmen were considerably hurt. After this accident, the hoisting 

 was obliged to be stopped till a new cylinder could be cast, and the 

 time was occupied in further strengthening the various portions of the 

 ponderous machinery. Operations, however, were soon renewed, 

 and on the 15th of October, the tube was raised to its permanent 

 level of 100 feet above high-water-mark. 



The other tubes are to be floated and hoisted as soon as the pre- 

 parations can be made. When all the tubes are in place, they are to 

 be firmly bolted to the piers, and those in each line will be firmly con- 

 nected together, and after this the extremities of each line are to be 

 lowered about 15 inches, by removing false foundations, and this will 

 add materially to the strength of the whole. Rollers are placed 

 under the tubes on the two abutments, to allow of contraction or ex- 

 pansion with the changes of the weather. The whole iron passage 

 is 1,841 feet long. The expense of the whole work will be about 

 600,000 pounds sterling. Derived from the Lo?idon Quarterly for October. 



NOVEL SUSPENSION BRIDGE AT CHESTER (WALES). 



IT was necessary to erect this bridge in a situation where it was 

 found advisable to dispense with piers and suspension-rods projecting 

 above the level of the road, and as the ravine to be crossed was 150 

 rods wide, and it was doubtful whether a proper foundation for the 

 erection of heavy stone piers could be obtained, recourse was had to 

 what is called the self-adjusting principle. The chain-rods are made 

 of the best seven-eighths round iron, in lengths of 15 feet each, with 

 secure lock-joints placed alternately. Across these are fitted flat bars 

 above and below, about six feet apart, upon which the wooden planks 

 forming the platform are firmly secured by bolts and nuts screwed up 

 from below. The chain rods are secured at one end to a massive stono 

 pier, by strong cramp plates and bars, built in from the foundation on 

 the Grosvenor side, while the stone pier at the other end of the bridge 

 is formed into a pit. On the top of this, resting on cast-iron girder 

 beams and pedestals, is placed a very strong grooved barrel, around 

 which each of the chains is made to take one turn, descending to a 

 strong cast-iron plate, which is suspended near the bottom of the pit 

 at the depth of 30 feet, to which it is fastened. Upon this plate a mass 

 of masonry is built, forming a weight sufficient to counterbalance the 

 whole weight of the rest of the bridge, and keeping the chain-bars in 

 a proper state of tightness, as well as providing for contraction and 

 expansion. We thus have the novel plan of a suspension bridge which 

 is fastened at one end to a pier of masonry, while at the other the sus- 



