Compressed Air Work And Diving 1909

BARMOUTH BRIDGE. 57 ing, and, until the rock was cleared away from under thc cutting edge, they carriecl the whole weight sus- pended by links. When ready, thc screws were turneel by small capstans, and the cylinders alloweel to descend. The bottoming up was on solid granite, and an interest- ing detail was the 6-in. angle bar, which was placed underneath the cutting- edge to prevent its further penetration, and which also to a certain extent inereased the bearing area over the granite. (See Plan 515, Fig. 6.) The filling was of solid brickwork. The Barmouth cylinders (see Fig. 7) were 8 ft. in diameter, with an inner tube 3 ft. 9 in. in diameter, which latter terminatecl in a beil mouth to allow room for exeavation rounel the cutting edge. The space between the two shells was filled with concrete to give the necessary kentledge as the work proceecled. Fig. 8 shows the method of sinking. The cylinders were guided in their descent by four piles, to which were boltecl angle bar rings encircling the cylinders. Between these and the cylinders 8-in. by 6-in. runners were placed and kept in position by angle cleats riveted to the sides of the rings. The buekets containing the exeavateel material were hoisteel by means of a -f-in. diameter Steel bond passing through a stuffing box in the top plate of the lock, and passing round the drum of an orelinary windlass placed on the top of the lock. On reaching the bottom of the lock the bueket was swunp- into the o entrance chamber, and, after the air had been exhausted, was lifteel out by means of a second windlass also placecl on the top of the lock. The actual staging was slightly different to that shown on account of the presence of the olcl viaduct during the construction, and of existing fendering, to which the guide piles were bracecl. The bridge is a swing- one carryinø- a single line and