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The Adhesion Principle.

The method of traction on mountain railways of other countries is mostly by some system of rack-rail. Herein the Rimutaka Incline differs, in that traffic is operated solely by adhesion. In between the usual parallel rails, at a height of some 6½ inches, is the centre rail. This is a double headed rail mounted on its side, on heavy longitudinal timbers; which, in turn, are securely fastened to brackets bolted to the ordinary transverse sleepers. The centre rail commences at the top end of the Cross Creek yard and has its termination some distance inside the south portal of the Summit tunnel. To assist the drivers in locating the latter end of the rail a gong is placed on the tunnel wall, twenty feet from the end of the centre rail. This gong is operated through treadle motion, by the wheels of passing vehicles.