Of the many engineering wonders of the Home railways, few exceed in interest the Severn Tunnel, the jubilee of the opening of which has just been celebrated by the Great Western Company. This is the longest subaqueous tunnel in the world. It is 4 miles, 624 yards long, and 2¼ miles of the tunnel actually lie beneath the River Severn estuary, in which neighbourhood the tides are the highest in Europe. The tunnel carries the Great Western main-line between London and South Wales, and also handles a heavy traffic between northern points and the West Country. The work of construction was begun in 1873, and completed in December, 1886. The total cost was nearly two million pounds. At its greatest width, the tunnel measures 26 ft., and its height to roof at centre is 20 ft. In the work of construction there were employed 3,628 men, and approximately 76½ million bricks were put into the structure. The engineers were Sir John Hawkshaw and Charles Richardson, and the contractor Thomas A. Walker. A large and expensive pumping plant is constantly at work keeping the tunnel dry, from ten to thirty million gallons of percolating water being raised daily. The maintenance of the tunnel lining is effected by forcing, from time to time, liquid cement, under pressure, behind the brickwork. Replacing an old steam ferry service, the Severn Tunnel shortened the journey between Bristol and Cardiff by 1½ hours.