suitable radius, and can only need turning end for end to form a curve
in the direction required. The rails weigh 9 lb., 14 lb., 19 lb., and 24
lb. per running yard, and are very similar to the rails used on the main
railways of France, except that their base has a proportionally greater
width. As to the strength of the rail, it is much greater in proportion
to the load than would at first sight be thought; all narrow-gauge
railways being formed on the principle of distributing the load over a
large number of axles, and so reducing the amount on each wheel. For
instance, the 9 lb. rail used for the portable railway easily bears a
weight of half a ton for each pair of wheels.

The distance between the rails differs according to the purpose for
which they are intended. The most usual gauges are 16in., 20 in., and
24in. The line of 16 in. gauge, with 9 lb. rails, although extremely
light, is used very successfully in farming, and in the interior of
workshops.

[Illustration: Fig. 3. Fig. 4. Fig. 5.]

A length of 16 ft. 5 in. of 9 lb. steel rail, to 16 in. gauge, with
sleepers, etc., scarcely weighs more than 1 cwt., and may therefore be
readily carried by a man placing himself in the middle and taking a rail
in each hand.

Those members of the Institution who recently visited the new port of
Antwerp will recollect having seen there the portable railway which
Messrs. Couvreux and Hersetit had in use; and as it was these works at
the port of Antwerp that gave rise to the idea of this paper, it will be
well to begin with a description of this style of contractor's plant.