get out. Through the pipes cement was pumped until finally it was not possible to shoot any more into the crevice under very heavy pressure. This was allowed to set for approximately three months. When the bulkhead door was opened it was found that the inflow had practically stopped. The bags of clay were completely cemented together and a detour was cut at this point to approximately , to get round the crevice, and when the men had passed it they worked back to the original line of excavation. The section of the tunnel that had been sealed up was cut through, the detour filled in, and the original straight line of excavation restored. After going about past the crevice, they struck another small fissure, which was apparently a section of the original one, and water suddenly flowed in at the rate of about an hour. This was not sufficient to stop the progress of the work, but pumps were installed to cope with the inflow. Soon after the men began to work on the up-grade, and here great care had to be exercised to prevent the material falling back on them. The material was cut out by channelling machines, which allowed it to be removed without difficulty. Eventually the work broke through and the opening at the Long Nose Point side was in sight. Their calculations had been made with remarkable accuracy. The centre line, when the tunnel was connected, was only 1/8th of an inch out, while the levels were absolutely correct. Despite careful lining leaks kept occurring. The tunnel was flooded about 1930, whether intentionally to avoid continual pumping or as the result of a sudden inrush of water, is not clear. In 1952 the Electricity Commission of New South Wales was formed to take over the generation of all electric power in NSW. The power stations in White Bay and Ultimo were taken over, but the tunnel and its cables remained the property of the State Rail Authority. During the construction of the Sydney Harbour Bridge the railway communication cables were re-routed via the Bridge. The electricity cables in the flooded tunnel were completed sheathed and remained in use until 1969, but are no longer used due to ample supplies of electricity now available on the north side of the harbour from electricity substations. Description The tunnel is lined with concrete in some areas, cast iron