Page:Walker (1888) The Severn Tunnel.djvu/56

Rh to the bottom, 10 feet being lined with brickwork below the tubbing.

This brickwork carried four wrought-iron girders, on which the pole-cases of the 26-inch plunger-pumps were fixed. There was a small iron door 2 feet square in the iron tubbing of the shaft opening outwards, through which access could be obtained to a cross-heading leading to the main heading from the bottom of the Old Pit, and in the brickwork between two of the wrought-iron girders was fixed a sluice by closing which water could be excluded from the pit, or admitted by opening it.

The girders when fixed proved too weak for the work they had to do, and an ordinary cast-iron pipe 15 inches in diameter was placed under one of the girders as a column. This pipe had, of course, a large flange at the top which afterwards proved a serious obstacle in the way of fixing other pumps. The valve, by which the quantity of water to be admitted to the pit was regulated, instead of being actuated by long rods brought up above the highest level of the water, was fitted with an ingenious (?) apparatus by which it was intended to shut or open it by turning on the pressure of water obtained from a spring behind the iron tubbing about 100 feet above the valve. When the shaft was full of water the action of this arrangement was most uncertain, and was the cause of much of the difficulty encountered in clearing the tunnel of water.

In the manner above described the work was