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The Tower Subway
under the River Thames, Tower Hill to Vine Street, London, UK
associated engineer
Peter William Barlow
James Henry Greathead
date  February 1869 - 7th April 1870
era  Victorian  |  category  Tunnel  |  reference  TQ333806
ICE reference number  HEW 233
The world's first sub-aqueous tunnel, Thames Tunnel, was completed in 1843, and despite the severe difficulties encountered in constructing it, the use of tunnelling shields as a construction method was proven. The second tunnel under the Thames, The Tower Subway, used this technology too, in an improved form. The Tower Subway is the first cast iron-lined tunnel in Britain and it paved the way for the development of the London Underground.
The Tower Subway runs under the Thames from Tower Hill in the City of London to what was Vine Street, a short street that once ran from the river's south bank to Tooley Street on the site now occupied by London City Hall. The subway was constructed under an Act of Parliament of 1868, which established The Tower Subway Company with three directors and capital of 12,000.
Its engineers were Peter William Barlow (1809-85) and his assistant James Henry Greathead, with Peter Barlow junior as resident engineer. Greathead had joined Barlow's staff in 1864.
Barlow was born in Woolwich in London and in his early career he worked with Henry Robinson Palmer on extensions to the London Docks. He also worked on the Liverpool & Birmingham Canal and later worked on railways under Sir William Cubitt. He became interested in the design of long span bridges and it was while working on the original Lambeth suspension bridge (1862, demolished) that he conceived an idea for tunnel construction.
The piers for the bridge were constructed using cast iron cylinders driven into the riverbed. Barlow had the idea of using such cylinders horizontally in order to tunnel underneath the river. He took out a patent in 1864 for a tunnelling shield design that consisted of a wrought iron or steel cylinder with cutting plates at one end. The shield was designed to be jacked forward and the tunnel lined with cement-jointed cast iron linings. In 1868, he added a diaphragm that enabled compressed air to be used to help keep the tunnel sides stable during digging.
The Tower Subway was the first use of Barlow's shield. Greathead helped design the shield and supervised its construction. The horizontal tunnelled section of the subway is 900ft long and 7ft in diameter. The whole system, including the two end vertical shafts is 1320ft long. It took only14 weeks to complete the tunnelling, demonstrating the feasilibity of speedy tunnel constructing and paving the way for London's Underground system (the Tube) to come. Greathead would play a leading part in the construction of the Tube.
The shaft contractor, Thomas Tilley, began sinking the Tower Hill shaft in February 1869. The access shafts are 10ft 2in in diameter and 60ft deep. The only visible sign above ground left to us now is a cylindrical brick kiosk outside the gates of the Tower of London, which was the original toll booth on the north side of the river.
The shield dug a tunnel slightly larger than the internal diameter of the iron lining ring pieces, which came in 18in lengths. These were bolted into place behind the shield and liquid cement forced into holes in iron rings so as to bond them to the London clay of the walls. At its greatest depth, the tunnel is 48ft below the high water mark.
The Tower Subway was designed to accommodate 12-seater iron carriages for ferrying passengers through its length. A standing 4hp steam engine was installed, which operated the lift in the Tower Hill shaft and the 2ft 6in guage train using a cable haulage system connected to it. The journey time was around 3 minutes and cost tuppence for first class and a penny for second class. This is the first 'tube' railway in the world.
However, passengers were few, as people could cross the river using London Bridge for free. After only a few months, the railway was abandoned and the tunnel used as a foot passage. The last train ran on 7th December 1870. Around a million people a year paid the toll and used it on foot, up until the building of Tower Bridge (1894) close by another free crossing. At that point the subway was closed.
In 1897, another Act of Parliament enabled the subway to be sold to the London Hydraulic Power Company for 3,000. It is still in use as a cable duct tunnel, serving the communications industry.
Resident engineer: Peter Barlow jnr
Shaft contractor: Thomas Tilley
Research: JJ
"Underground to Everywhere" by Stephen Halliday
Sutton Publishing, Stroud, 2004
reference sources   CEH LondBDCE2

The Tower Subway