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Tower Bridge, London

It took 8 years, 5 major contractors and the labour of 432 construction workers to build Tower Bridge and was completed in 1894. Two massive piers were sunk into the river bed to support the construction and over 11,000 tons of steel provided the framework for the Towers and Walkways. This framework was clad in Cornish granite and Portland stone to protect the underlying steelwork and to give the Bridge a more pleasing appearance. When it was built, Tower Bridge was the largest and most sophisticated bascule bridge ever completed ("bascule" comes from the French for "see-saw"). These bascules were operated by hydraulics using steam to power the enormous pumping engines. The energy created was stored in six massive accumulators and these fed the driving engines which drove the bascules up and down. Despite the complexity of the system, the bascules only took about a minute to raise to their maximum angle of 86 degrees. Today, the bascules are still operated by hydraulic power, but since 1976 they have been driven by oil and electricity rather than steam. London January 2011

  

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Taken on January 10, 2011