Compressed Air Work And Diving 1909

62 COMPRESSED AIR WORK. when resting at both encls on rock or other hard <rrouncl and unsupported in the miclclle. Above 26 ft. 6 in. the caisson was a shell only, and therefore had to be strutted with timbers varying from 15 by 15 in. to 12 by 12 in. Access to the working chamber was obtained by three shafts. The shafts were of novel design, being, in faet, two shafts run into one (see Figs. 10 and 11) and separated by an iron ladder constructed of 2-in. wide flåts riveted to the sides of the shaft by angle bars running the whole length of the shaft on one side, and by short cleats on the other. By this lacider the men clescendecl inside the small shaft, which was 2 ft. in diameter. The other portion, 4 ft. in diameter, was for material. An angle bar ran the length of the lackler riveted to the centre of the flats, and acted as a protection to the fingers and feet of the men, should they happen to be in the shaft at the same time as a bueket. The lock (see Fig. 11) was circular, 8 ft. 6 in. in diameter by 6 ft. high. The entrance chamber was D-shaped, and boltecl on to the outsicle of the lock, the joint between the two being made with reel leacl. The air pressure was raised and lowered from the outsicle by levers, and from the inside with keys by persons authorised to use tb em. The special feature of the lock was the bueket chamber, which was 3 ft. in diameter and 5 ft. 6 in. high. This chamber had a cloor which opened downwards, and which was closecl after a bueket had entered by a wire bonel and hook, which was fasteneel to a lug on the cloor by hanel each time the cloor was closecl. The bond passed round a clrum which was fixed 011 a shaft driven by a motor placed 011 the outsicle of the lock and put into gear by a friction clutch. The bonel on which the bueket was hung- was 1 in. diameter, and passed through a stuffing box in the lid of chamber. This i 00