This keeper of the city gate represents the survival of the fittest, the very cream of his profession. The chances are that he began his railroading off in some lonely way station on a branch line, developed qualities that brought him to the quick and favorable attention of his chiefs, then advanced steadily along the rapid lines of promotion that railroading holds for some men. He is one of three men, who, for certain hours, hold the keeping of the complicated city gate within their own well-drilled minds. The tower is the mind, the brain centre, the ganglion, of that city gate; but the tower is only wondrously mechanical, after all; the mind of the careful towerman is the mind that controls all the mechanism. To the average traveller, the city gate is a thing that impresses itself upon his mind by its exterior and interior beauty, or its convenience of arrangement. He notes the broad concourses, the ample entrances and exits, the compelling magnificence of the public rooms, the great sweep of the train-shed roof, but beyond that train-shed roof is a tangle of tracks and signals about which he does not worry his busy head. Those tracks and signals represent more truly the station than the mere architectural magnificence of its outer shell. They are a tangle and a maze, apparently, but a tangle and maze that must represent skill and ease in their tremendous operation. They are neither tangle nor maze to the shirt-sleeved men in the tower. They must know each track, each switch-point, each signal as intimately and familiarly as they know the fingers of their hands. Every mechanical device is employed to simplify the tangle for the comfort of the busy minds that must constantly employ themselves in solving it. In the big watch-tower--the "control" of the terminal--there is a map that is more than map. It depicts in miniature all the tracks and switches and signals that lie without and roundabout the tower; but this map shows switches and signals changing as the switches and signals of the train-yard change. It brings the distant corners of the terminal in closer touch with the towermen. In fog or blinding storm, this track model is invaluable--a veritable compass set within the brain of the terminal.