Page:Walker (1888) The Severn Tunnel.djvu/263

158 and opened the sluice gradually as the pumps were able to take the water. The sluice was opened on 21st December, and the pressure was rapidly reduced from 57¼ lbs. on the square inch to 30 lbs.

Sir John Hawkshaw then determined that it was necessary to provide pumping-plant to pump the whole of the water from the spring, and not to subject the brickwork of the tunnel to the enormous pressure it would have to sustain to exclude this water.

Arrangements were made with me to sink a large shaft at the side of the tunnel, 29 feet in internal diameter. In this shaft were to be fixed six large pumps with six 70-inch Cornish beam-engines fixed in a house which entirely covered the shaft. It was also determined to fix two 65-inch engines with two new pumps in the pumping shaft at 5 miles 4 chains, and two 41-inch beam-engines with 29-inch pumps in the shaft at Sea- Wall.

A Guibal Fan, 40 feet in diameter and 12 feet wide, was ordered by the Company, and the designs made for the necessary buildings comprising fan-house, engine-house, and boiler-house. Two Lancashire boilers, each 26 feet in length by 7 feet in diameter, were provided for the fan, and a space provided for a third boiler, which was afterwards added. Twelve Lancashire boilers 28 feet in length, and 7 feet in diameter, were provided for the pumping engines at Sudbrook, and a new engine and boiler-house were built at 5 miles 4 chains, in which