Iron Bridge Gorge

The Iron Bridge across England's longest river,the severn,is the world first iron bridge.At one time,the surrounding area was a remarkable concentration of industrial activity.Today the area under the bridge and on both sides known as the Ironbridge Gorge,is a world heritage site,in recognition of its outstanding importance in the early development of industrialisation.The Iron Bridge was built in 1779 and was opened on New Year's day in 1781.It is a testimony of the first large-scale use of iron for structural purposes in the world and a remarkable demonstration of the utility and versatility of iron for construction.With a span of 30 metres,the graceful semi-circular arch reached across the gorge of the Severn at its narrowest point.The Iron Bridge was not only a singular example of new engineering but also a tremendous success.Its symbolic significance was great,not only in Britain but throughout Europe and the United States.
Proper international fame and recognition came with the designation of the Gorge and the bridge as a world Heritage Site in 1986.It is the first industrial area to be listed as a World Heritage Site.

London Underground

An underground is an electrically operated underground railroad.Its first construction was first stimulated in the 19th century.The world first underground was the brainchild of Charles Person,solicitor of the cityof London.The first phase between Farrington to Paddington was begun in 1860 and completed in 1863.The construction was done in the cut-and-cover method.An areached brick structure was first constructed in an open trench and then earth was backfilled over it.The lo9comotive power for the train being supplied by steam,the underground then had a sulphurous atmosphere.In spite of that,the subway attracted about 10 million pessengers in its first year of operation.Its primary success encoureged additional construction in 1886.Instead of the old cut-and-cover method,this time a new construction device was used.James Henry Greathead developed a steel made cylindrical tube which could be forced forward into the ground by means of hydraulic jacks.This method made it possible to dig tunnels deep enough not to disturb surface buildings and traffic.The depth of the tunnels then necessitated the installation of lifts at the stations.Electrification of the lines made it possible.Later on.lift were replaced by escalators.With the use of electricity,great expansion took place and by the early 1970s London had 102 miles of underground lines,the second largest in the world.The largest underground (or subway as it is called there)is now in New York.The increasing automobile congestion in metropolitan cities has spurred the building of new underground or subway systems in other cities too.