History of rail transport
James Watt, a Scottish inventor and mechanical engineer, greatly improved the steam engine of Thomas Newcomen, hitherto used to pump water out of mines. Watt developed a reciprocating engine in 1769, capable of powering a wheel. Although the Watt engine powered cotton mills and a variety of machinery, it was a large stationary engine. It could not be otherwise: the state of boiler technology necessitated the use of low pressure steam acting upon a vacuum in the cylinder; this required a separate condenser and an air pump. Nevertheless, as the construction of boilers improved, Watt investigated the use of high-pressure steam acting directly upon a piston. This raised the possibility of a smaller engine, that might be used to power a vehicle and he patented a design for a steam locomotive in 1784. His employee William Murdoch produced a working model of a self-propelled steam carriage in that year.
The first full-scale working railway steam locomotive was built in the United Kingdom in 1804 by Richard Trevithick, a British engineer born in Cornwall. This used high-pressure steam to drive the engine by one power stroke. The transmission system employed a large flywheel to even out the action of the piston rod. On 21 February 1804, the world's first steam-powered railway journey took place when Trevithick's unnamed steam locomotive hauled a train along the tramway of the Penydarren ironworks, near Merthyr Tydfil in South Wales. Trevithick later demonstrated a locomotive operating upon a piece of circular rail track in Bloomsbury, London, the "Catch Me Who Can", but never got beyond the experimental stage with railway locomotives, not least because his engines were too heavy for the cast-iron plateway track then in use.
The first commercially successful steam locomotive was Matthew Murray's rack locomotive "Salamanca" built for the Middleton Railway in Leeds in 1812. This twin-cylinder locomotive was not heavy enough to break the edge-rails track and solved the problem of adhesion by a cog-wheel using teeth cast on the side of one of the rails. Thus it was also the first rack railway.
London Underground
The idea of an underground railway linking the City of London with the urban centre was proposed in the 1830s, and the Metropolitan Railway was granted permission to build such a line in 1854. To prepare construction, a short test tunnel was built in 1855 in Kibblesworth, a small town with geological properties similar to London. This test tunnel was used for two years in the development of the first underground train, and was later, in 1861, filled up. The world's first underground railway, it opened in January 1863 between Paddington and Farringdon using gas-lit wooden carriages hauled by steam locomotives. It was hailed as a success, carrying 38,000 passengers on the opening day, and borrowing trains from other railways to supplement the service. The Metropolitan District Railway (commonly known as the District Railway) opened in December 1868 from South Kensington to Westminster as part of a plan for an underground "inner circle" connecting London's main-line stations. The Metropolitan and District railways completed the Circle line in 1884, built using the cut and cover method. Both railways expanded, the District building five branches to the west reaching Ealing, Hounslow, Uxbridge, Richmond and Wimbledon and the Metropolitan eventually extended as far as in Buckinghamshire, more than from Baker Street and the centre of London.