The side fronting upon the street is usually handsomely embellished, for it is this side which the public sees as it approaches, and all railroads know that to make a good impression is to do good advertising. So with the main waiting-room, which always lies directly behind the street doors. Here marble, mosaic and gilding are always in evidence and no opportunity is lost to impress the travelling public with the wealth and magnificence of the road which it is using. On either side of the main waiting-room are smaller waiting- and retiring-rooms, there is a row of ticket-booths, a news-stand, telephone booths, baggage-rooms, a dining- and lunch-room and, of course, inevitably, the long rows of seats, back to back, where the waiting public spends so many weary minutes. In the stories overhead are the executive offices of the various roads—as many of them as there is room for—but to these the general public seldom penetrates. Beyond the swinging doors along the side of the waiting-room opposite the entrance is the main platform or concourse, and from it, stretching down between the tracks like long fingers, are the narrow cement platforms upon which the passengers alight or from which they mount to their trains. The tracks are laid in pairs, and a platform extends between every pair, each platform thus serving two tracks, one on either side. Overhead is the great echoing vault of the train-shed with its mighty ribs of steel, stretching in one enormous arc across the tracks beneath—a marvel of engineering skill, if not of architectural beauty. This is what is known as the head-house plan, and is the ideal one for the passenger, since it permits him to go to and from his train without crossing any tracks or climbing to any overhead bridges. It is, however, expensive for the railroads since, of course, all through trains must be backed out and switched around until they are headed on their way again—a process which requires no little expenditure of time and energy, as well as money. However, in a great city, a right of way which would enable the through trains to continue straight onward toward their destination is frequently so expensive that it is cheaper to back them out the way they came in, and send them by a detour around the city.