sixteen wagons, each having a double equilibrium tipping box containing
11 cubic feet, and all accessories, represents a weight of 20 tons--a
very light weight, if it is considered that all the materials are
entirely of metal. Its net cost price per mile is 450_l_., the wagons
included.

Large contracts for earthwork with horse haulage are carried on to the
greatest advantage with the railway of 20 in. gauge and 14 lb. rails.
The length of 16 ft. 5 in. of this railway weighs 170 lb., and so can
easily be carried by two men, one placing himself at each end. The
wagons most in use for these works are those with double equilibrium
tipping boxes, holding 18 cubic feet. These are at present employed in
one of the greatest undertakings of the age, namely, the cutting of the
Panama Canal, where there are used upward of 2,700 such wagons, and more
than 35 miles of track.

A mile of these rails of 20 in. gauge with 14 lb. rails, together with
sixteen wagons of 18 cubic feet capacity, with appurtenances, costs
about 660_1_., and represents a total weight of 33 tons.

This description of material is used for all contracts exceeding 20,000
cubic yards.

A very curious and interesting use of the narrow-gauge line, and the
wagons with double equilibrium tipping-box, was made by the Societe des
Chemins de Fer Sous-Marins on the proposed tunnel between France and
England. The line used is that of 16 in. gauge, with 9 lb. rails.

The first level of the tunnel, which was constructed by means of a
special machine by Colonel Beaumont, had only a diameter of 2.13 m. (7