The construction of the subway was begun at the Public Gardens, where an incline, a hundred yards long, carries the surface lines into the tunnel, passing under the edge of Boston Common to Tremont Street. It is joined by a branch subway from Pleasant Street, where another incline leads to the surface. From this junction the subway proceeds beneath the Tremont Street side of the Common to Park Street, which is the central point of the system. Thence it is carried directly beneath Tremont Street to Scollay Square, and by means of a bifurcation under Hanover Street on the one hand and Cornhill on the other to a junction under Washington Street. The tunnel continues under Washington Street to Haymarket Square, and immediately rises by an incline to Causeway Street, where it connects with both the surface and the elevated lines. Wherever possible, the subway was carried out by open excavations, and, as in the Paris Métropolitain, by the old-fashioned “cut and cover” method. The roof of the tunnel is generally about three feet below the surface, though in some places considerably lower. At and near the stations the subway sides are lined with white glazed bricks, whitewash being used elsewhere. There are five stations in the Boston shallow underground, viz. at Boylston Street, Park Street, Adams Square, Scollay Square, and Haymarket Square. These are approached by short stairways, protected from the weather by neat clock-surmounted kiosks, or small iron structures, in shape resembling our cab shelters, and placed at convenient points, either on the sidewalks or--where there is sufficient width--in the centre of the [Illustration: FIG. 23. BOSTON SUBWAY, SHOWING ENTRANCE AT THE PUBLIC GARDENS _By permission of the_ _London County Council_] roadway. Passengers can thus, by about twenty-five steps, go to and from the platforms in a few seconds. The ticket-offices are at the bottom of the stairways. The passenger returns at Park Street (the busiest station) are among the largest in the world, being 28,000,000 per annum. The Boston surface street cars adopt the overhead trolley principle of electric traction, and the elevated railway-cars the third rail system, both these systems being continued throughout the subway. The subway is illuminated electrically, but a considerable amount of natural light is also obtained, especially at the stations; and Captain Piper, deputy of the New York Police, when on a visit to London last February, discussing the question of ventilation in tube railways, gave it as his opinion that the freshest air he had “struck” in an underground railway was at Boston. “The air,” he said, “is excellent.”