The masonry for the side walls is obtained either from the tunnel itself or from a neighboring quarry, and varies in character according to the pressure; but the face of the arch is always of cut or artificial stones, the latter being 7 to 1 cement concrete. Where the alinement heading, or the “gallery of direction,” joins the curving portion of tunnel No. 1, the section is very much greater, and necessitates special timbering. =Transport (Italian Side).=--A small line of railway, 2 ft. 7¹⁄₂ ins. gauge, with 40-lb. rails, enters all three portals; but since the construction of a wooden bridge over the Diveria, the route through the “gallery of direction,” across heading No. 2, to tunnel No. 1, is used exclusively; this railway leads to the face in both headings, and, where convenient, from one heading to the other by the cross-galleries. Different types of wagons are in use; but in general they are four-wheeled, non-tipping box wagons, supplied with brakes and holding 2 cu. yds. of débris. A special type of locomotive is used, designed to pass round curves of 50 ft. radius, and supplied with a specially large boiler to avoid firing in the tunnel. [Illustration: FIG. 57.--General Details of the Brandt Rotary Drills Employed at the Simplon Tunnel.] =Method of Working.=--The drilling-machines employed are of the Brandt type, Fig. 57, and are mounted in the following manner: A small four-wheeled carriage supports at its center a beam, the shorter arm of which carries the boring mechanism and the longer a counterpoise; near its center is the distributor. In the short arm is a clamp holding the rack-bar or butting column, which is a wrought-iron cylinder with a plunger constituting a ram, and is jammed by hydraulic pressure between the walls of the heading, thus forming a rigid support for the boring-machine, and an efficient abutment against the reaction of the drill. This rack-bar can be rotated on its clamp in a plane parallel to the axis of the beam. Three or four separate boring-machines can be mounted on the rack-bar, and can be adjusted in any reasonable position.