A road or way of parallel iron or steel rails on which the wheels of carriages, run, and supported on a bed or structure. Railway is the usual word in England, but railroad is common in the United States. The modern railroad is an adaptation of the old horse tram-roads, with cast-iron flange rails, used for hauling coals early in the century. The Stockton and Darlington Railway, the first line with locomotives, was opened in October, 1825. The first passenger line in the United States was the Baltimore and Ohio, opened in 1830. There are now over 190,000 miles of railroad in the United States, 160,000 in Europe, and about 450,000 in the world. Rails are now usually laid to the standard width or gauge of 4 feet 81/2 inches. The iron rail, formerly wholly in use, has been widely replaced by steel. The steam locomotive known as the Rocket, invented by Robert Stephenson in 1829, weighed 8 or 9 tons; locomotive engines now weigh from 35 to 50 tons, and draw a train averaging from 400 to 500 tons. In 1838, on the London and Birmingham line, a speed of 20 miles an hour was obtained. Now a speed of 50 miles an hour, including stoppages, is maintained on one of the New York Central trains between New York and Chicago for a distance of nearly 1,000 miles, and 60 miles an hour is made on some roads for shorter distances. A straight and horizontal surface being the standard of perfection for railroad-making, sharp curves and steep gradients are regarded as evils. Routes are therefore shortened by embankments, cuttings, tunnels, and bridges. Among the remark-able railway tunnels are the St. Gothard and Mont Cenis in Switzerland, and the Hoosac Tunnel in Massachusetts. Of railway bridges the most wonderful are the Forth Bridge, Victoria Bridge (Montreal), Britannia (Menai Strait); also those at St. Louis, Rock Island, Louisville, and Niagara. Cars such as Pullman cars, with entrance at each end, are common in the United States and Switzerland; those entering at the sides are usual in Britain and other parts of Europe.