Page:Walker (1888) The Severn Tunnel.djvu/182

Rh lengths averaging 20 feet were taken out in the Pennant rock, and the arch pushed on rapidly. Although the rock was good at this point, and rapid progress was made, no length was allowed to be executed without timbering.

The arch was completed from 5 miles 4 chains pit to within 30 feet of the point where the Great Spring had broken in, in 1879. The heading was pushed forward westward from 5 miles 4 chains, and a break-up commenced in the conglomerate rock.

Every yard of ground that was opened at this pit gave additional quantities of water; and I found it necessary, in addition to the two 28-inch pumps which were working there, to put down two 18-inch plunger-pumps, worked by a large horizontal engine.

The Marsh Pit was lowered to the new gradient, and the two 15-inch plunger-pumps were refixed there. We had recommenced to drive the headings east and west, and a length of about 60 yards of tunnel was completed adjoining the pit. The old heading was lowered to the new gradient for a distance of about 200 yards westward from the pit, and a break-up had been commenced about 100 yards west of the pit.

The Hill Shaft had also been lowered to the altered levels, and two 15-inch plunger-pumps had been fixed in that shaft, with a new pumping-engine; and the heading had also been lowered for a distance of about 150 yards west of the pit, and a break-up started about 100 yards from the pit.