Page:Walker (1888) The Severn Tunnel.djvu/74

Rh On obtaining, however, full particulars of the manner in which the headings had been worked from the Old Pit, especially the heading running westwards into which the Great Spring had burst, I thought that it would be quite possible to stop the mouth of the heading and the flow of water from the Great Spring by lowering into the shaft two shields made to fit, as nearly as possible, to the interior of the shaft, and strutted across the shaft in a secure manner. The difficulty was that the mouth of the heading was then 140 feet below the surface of the water; but, having obtained the sanction of Sir John Hawkshaw to make the attempt, my plans were made, and as early as the 6th January, eighteen days after the contract was signed, operations were commenced.

According to the best information we were able to obtain from those who had been in charge of the works, the quantity of water running into the heading under the river was not more than 2,000 gallons per minute, and to deal with this we had, in the Iron Pit, two 26-inch plunger-pumps, each capable of lifting 2,500 gallons per minute, and in the Old Pit an 18-inch plunger-pump capable of lifting 1,200 gallons per minute; so that if we could by any means succeed in stopping back the Great Spring, we had ample power to clear the rest of the works of water.

The construction of the shield and the method of securing it in the shaft are shown upon the accompanying plate.