Since the partial opening of the Greenwich Railway in 1836, a large extent of railways has been constructed in and about the metropolis, and convenient stations have been established almost in the heart of the city. Sixteen of these stations are within a circle of half a mile radius from the Mansion House, and above three hundred stations are in actual use or in course of construction within about five miles of Charing Cross. The most important lines recently opened for the accommodation of the London local traffic have been the London, Chatham and Dover Metropolitan Extensions (1861), the Metropolitan (1863), the North London Extension to Liverpool Street (1865), the Charing Cross and Cannon-street Extensions of the Southeastern Railway (1864-6), and the South London Extension of the Brighton Railway (1866). Of these railways, the London, Chatham and Dover carried 5,228,418 passengers in 1867; the Metropolitan, 23,405,282; the North London, 17,535,502; the Southeastern, 17,473,934; and the Brighton, 12,686,417. The total number carried into and out of London, as well as from station to station in London, in the same year, was 104 millions of passengers. To accommodate this vast traffic, not fewer than 3600 local trains are run in and out daily, besides 340 trains which depart to and arrive from distant places, north, south, east, and west. In the morning hours, between 8 30 and 10 30, when business men are proceeding inward to their offices and counting-houses, and in the afternoon between four and six, when they are returning outward to their homes, as many as two thousand stoppages are made in the hour, within the metropolitan district, for the purpose of taking up and setting down passengers, while about two miles of railway are covered by the running trains. One of the remarkable effects of railways has been to extend the residential area of all large towns and cities. This is especially notable in the case of London. Before the introduction of railways, the residential area of the metropolis was limited by the time occupied by business men in making the journey outward and inward daily; and it was for the most part bounded by Bow on the east, by Hampstead and Highgate on the north, by Paddington and Kensington on the west, and by Clapham and Brixton on the south. But now that stations have been established near the centre of the city, and places so distant as Waltham, Barnet, Watford, Hanwell, Richmond, Epsom, Croydon, Reigate, and Erith can be more quickly reached by rail than the old suburban quarters were by omnibus, the metropolis has become extended in all directions along its railway lines, and the population of London, instead of living in the city or its immediate vicinity as formerly, have come to occupy a residential area of not less than six hundred square miles!