Compressed Air Work And Diving 1909

ERST RIVER TUNNELS. 95 the shield then moved forward, the floors all the time remaining stationary, and supporting the rock face. These floors were also very useful in 2'iving- stanclino- room for the rock drills, and allowing them to be set up in the most favourable position. I here were two hyclraulic erectors of the ordinary type at the back of the shield, worked by a rack and pinion. The shields were fittecl with air pipes so that air could be admitted separately to each compartment, but for most of the time it was not found necessary to clo this, and the end of the inlet air main was kept about 30 ft. behind the shield. I here were three boiler-shaped locks in each bulk- head, the emergency lock at the top, and two others below, which could be used for either men or material. These bulkheads were built of concrete. A travelling platform, similar to the one at the Blackwall Tunnel (see Plate III.), was used for tighten- ing up the bolts from, grouting, and caulking. Eight medical locks were provicled, four each side the river, for treatment of clecompression symptoms (Fig. I5B)- Each contained two bunks for the patients, and one end was divided off to form an entrance chamber, so that a doctor could enter at any moment to attend a patient without lowering the pressure. A fresh patient could also be introcluced at any time during the treatment of another. The locks were warmed with electric heaters, and a telephone was fittecl so that the patient could com- municate with persons outside. In this connection it is interesting to note that medical locks were first used for the treatment of clecompression cases by Mr Moir during the driving of the first tunnel in New York under the IIudson River.