The Tower Subway
Today is the anniversary of the official opening of the Tower Subway in 1870. This deep tunnel, which took ten months to build and cost £16,000, was the world's first underground tube railway. The tunnel was lined with cast iron tubes in 18-inch sections 7/8th of an inch thick. It took passengers underneath the River Thames from Tower Hill on the north bank to the south side. The tunnel was designed and built by the English civil engineer and bridge builder, Peter William Barlow, in conjunction with the engineer, James Henry Greathead. Greathead developed Barlow's new method of digging deep tunnels, originally based on an earlier design by Marc Isambard Brunel, (the father of Isambard Kingdom Brunel), using an extremely efficient circular drilling shield. His improved design later became known as the 'Greathead Shield' [see this page on the history of Tunnelling]. Before this invention, all tunnels had been built by the 'cut and cover' method. The expertise Greathead gained in building the Tower Subway was invaluable when later tube lines were built.
Unfortunately, the Tower Subway only operated as a tube railway for about three months as it didn't make enough money and the company went bankrupt. The problem was that it was a narrow single bore tunnel (7-ft in diameter) using one small cable car, which ran on a 2-ft 6 track. The railway was powered by a 4 horse power stationary steam engine on the south side of the tunnel which pulled the cable car along on an endless cable. The conditions were cramped and the car, which only carried twelve passengers at a time, had to shuttle back and forth along the 1,430-foot long track - each journey taking about 70 seconds.
The tunnel was immediately converted to a pedestrian walkway, with the cables ripped out and gas lights installed, and it re-opened in November 1870. It became a very popular way to cross the river averaging some 20,000 customers a week each paying one halfpenny for the privilege. This was in spite of the fact that there was little headroom and the conditions were said to be 'creepy'! However, the subway eventually closed to the public shortly after the newly constructed Tower Bridge was opened in 1894.
In the 1920's, the tunnel was re-used as a route for water mains and hydraulic tubes, a major source of power in London at the time. Surviving damage during the bombing of World War II, the tunnel still carries water mains today and telecommunication cables instead of the hydraulic tubes which became obsolete in 1975.