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In 1869 a 410 m circular tunnel was dug through the London clay using a cast iron shield, an idea that had been patented in 1864 by Peter W. Barlow but never built.
A 762 mm narrow gauge railway was laid in the tunnel and from August 1870 a cable-hauled wooden carriage conveyed passengers from one end to the other. This was uneconomic and the company went bankrupt by the end of the year. The tunnel was converted to pedestrian use and one million people a year crossed under the river, paying a toll of a ha'penny.
The opening of the toll-free Tower Bridge nearby in 1894 caused a drop in income and the tunnel closed in 1898, after being sold to the London Hydraulic Power Company.
Today the tunnel is used for water mains.
The same shield method of construction was used in 1890 to dig the tunnels of the City and South London Railway, the first of London's electrified Tube railways and the first underground electrified railway in the world.
In 1864, Peter Barlow patented a method of tunnelling using a circular cast iron shield and to fill the gap between the tunnel lining and wall with lime or cement to prevent settling of the surrounding ground.
Unfortunately, Barlow failed to explain how he intended to fill such gaps between shield and tunnel wall with grout. He published a pamphlet in 1867 suggesting a network of tunnels with cars carrying up to twelve people.
More information: Historic UK
In 1868 authority was obtained for a tunnel under the Thames between Great Tower Hill and Pickle Herring Stairs near Vine Street (now Vine Lane), but there was a delay finding a contractor due to recent experiences with the Thames Tunnel until his former pupil James Henry Greathead tendered for £9,400.
Whilst Barlow patented his idea in 1864 for a tunnelling shield, he never constructed it: Greathead was accredited with the first shield construction for what is now known as the Tower Gateway complex in 1869. According to William Copperthwaite, who once worked under Greathead, both Greathead in England and Alfred Ely Beach in New York invented and constructed their own versions of tunnelling shields simultaneously and independently of each other.
Work began in February 1869 with the boring of entrance shafts, 18 m deep on the north bank and 15 m deep on the south bank. The tunnelling itself started in April using the circular Greathead shield.
Whilst many argue that the shield used was a Barlow-Greathead shield, William Copperthwaite says ... in 1868 [Barlow] provisionally patented a shield having near the cutting edge a transverse partition or diaphragm. Neither of these designs took practical form, and in 1869 Greathead in England and Beach in New York actually built and used shields having many features in common with Barlow's patents but differing from each other in details... Beach's shield resembled Barlow's patent of 1864, and Greathead's the provisional patent of 1868.
Copperthwaite puts to bed all arguments over origins of tunnelling shields as being the patented but unimplemented idea of Barlow's in 1864 but the actual construction of a different patented device by Greathead was built and first used on the Tower Subway and simultaneously in New York, Beach created and made his own shield independently of Barlow's and Greathead's designs.
More information: SciHi
Barlow lost out on credit because he never actually constructed one, only patenting the idea. Copperthwaite also reveals that Greathead was unaware of the 1868 provisional patent of Barlow's until 1895, a fact discussed in an 1895 Institution of Civil Engineers paper on the City and South London Railway acknowledged by Barlow.
A tunnel 410 m long was dug with a diameter of 2.026 m, a maximum of 20 m below the high-water level. This was bored through a stable layer of the London clay that lay 6.7 m below the river bed, below the soft alluvial deposits that had plagued the construction by Brunel of the earlier Thames Tunnel. This, combined with the simpler nature of the project -the excavation face was only one twentieth that of the Thames Tunnel- enabled faster progress.
Screw jacks drove the shield forward at a rate of 11.38 m each week. The under-river section was dug in fourteen weeks and the tunnel completed in December 1869.
While it is no longer used for hydraulic tubes, the tunnel still carries water mains. The hydraulic tubes, once a major source of power in the centre of London, have since been replaced by fibre optic telecommunications links.
A small round entrance building survives at Tower Hill near the Tower of London's ticket office, a short distance to the west of the main entrance to the Tower. This is not the original entrance but was built in 1926 by the London Hydraulic Power Company, with a ring of lettering giving the original date of construction and naming the LHPC. The entrance on the south bank of the Thames was demolished in the 1990s, and a new one has been built in its place. It is located just behind the Unicorn Theatre on Tooley Street, but there is no plaque to mark the site.
More information: Londonist
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