Compressed Air Work And Diving 1909

C O NIV A Y BRIDGE. 55 the cutting edge was of wrought iron—extencling right through it and half way through the length above. This was remedied by lining the fractured segments with wrought-iron plates, and filling the space behind with cement grout. Cast iron is not a suitable material for cylinder work, as not only are cylinders made of it liable to become fractured cluring- sinking, but this often happens after they have been standing for some years, and they are frequently seen bound on the outside with wroug-ht-iron bands. The Conway cylinders were sunk in order to shorten the span of the Conway tubular bridge, and thereby decrease the stress in the tube, which had become too great on account of the increase in the rolling load since the construction of the bridge. These cylinders were constructed (Fig. 6) of plates of mild Steel i-| in. thick, and were sent out from the yard in 5-ft. lengths. These were bolted together, as adclecl on site, by i-in. diameter turneel bolts, 8-in. pitch, and passing through two 4 by 4 by f in. angle bars on the inside. The joint between these was made by flat rubber and red lead. During the sinking these angle bars were used to support a ring of blue brick packed in sand, which considerably reducecl the amount of kentledge required to be piled on the top of the lock. The air-lock was fixed on a circular plate bolted on to the top length of the cylinder and stood above it. The two ends were semicircular, and one was divided off from the rest of the lock and formed the entrance chamber for the men. The lower part of the other end was cliviclecl into two hoppers with horizontal cloors opening upwards. Into these the excavated material, which had been hoisted by an electrically-driven winch placed inside the lock, was emptied. In the side of the locks were hinged cloors