Progress of the work—1881. alternately, with a considerable heap of clay in bags laid over the top for the sake of weight. When this was completed, the pumps were started again, and the clay was found to have effectually stopped the water.
At each end of the lengths of brickwork, where the water had broken in, a 6-ft. length of tunnel was immediately commenced, 4 feet thick; the ordinary work being only 2 feet 3 inches. These lengths were taken out as rapidly as possible, and brickwork in cement built in them, thus forming, in the chases which had been cut, a ring of brickwork nearly double the ordinary thickness to stop the water from travelling along the back of the work. This proved entirely successful, and though we had once or twice to repair the clay puddle on the top and replace the bags, we had no further trouble with the Salmon Pool.
Later on in the work we had a similar experience with a small lake, known as ‘The English Lake,’ but there we never had the same volume of water rushing into the tunnel, and had no necessity for stopping the pumps.
It was a most fortunate thing that this bursting in of the water from the Salmon Pool occurred before the long heading was completed; for had we broken through from the long heading on the west side of the river into the heading on the east side, it would have been impossible to stop the pumps and let the water rise in the tunnel till such time as