Page:Walker (1888) The Severn Tunnel.djvu/267

162 the alteration of the South Wales Union Railway is completed.

The permanent way consists for about 4 miles 29 chains in the tunnel of a longitudinal sleeper road, with a bridge-rail that weighs 68 lbs. per lineal yard; and the remainder of the Great Western standard pattern sleeper road, with an 86-lb. bull-headed rail and 43-lb. chair.

The rails are made of steel; the railway is well ballasted and well fenced.

The only stations are at Pilning and at Severn Tunnel Junction.

The works consist of three bridges under the railway, which have wrought-iron girders on brick abutments; three brick bridges and one wooden bridge over the railway; eight culverts; and the tunnel under the Severn, which is 7,664 yards long.

The tunnel is lined with vitrified brick in cement.

The sides, which rise about 7 feet above the rail-level, carry a semicircular arch of 26 feet diameter, which varies in thickness from 27 inches to 36 inches; and there is a brick invert, 18 inches to 3 feet thick, throughout the tunnel, which has a brick semicircular drain about 3 feet 6 inches wide over the centre, and a brick barrel-drain 5 feet in diameter under the invert. This latter carries the surface-water to a shaft at the north end of the tunnel, and drains the cuttings at both sides of the railway.

In addition to these there is an old heading 12 feet wide at the north end of the tunnel, which has been utilized for drainage purposes.

There are ventilating shafts at each side of the