a fixed cast-iron switch, and to let the workmen who drive the wagon
push it in the direction required. Planed switch tongues are also used,
having the shape of those employed on the normal tracks, especially for
the passage of small engines; the switches are, in this case, completed
by the application of a hand lever.

The portable turntable consists of two faced plates laid over the other,
one of thick sheet iron, and the other of cast iron. The sheet-iron
plate is fitted with a pivot, around which the cast iron one is made to
revolve; these plates may either be smooth, or grooved for the wheels.
The former are used chiefly when it is required to turn wagons or trucks
of light burden, or, in the case of earthworks, for trucks of moderate
weight. These plates are quite portable; their weight for the 16 in.
gauge does not exceed 200 lb. For engineering works a turntable plate
with variable width of track has been designed, admitting of different
tracks being used over the same turntable.

When turntables are required for permanent lines, and to sustain heavy
burdens, turntables with a cast iron box are required, constructed on
the principle of the turntables of ordinary railways. The heaviest
wagons may be placed on these box turntables, without any portion
suffering damage or disturbing the level of the ground. In the case of
coal mines, paper mills, cow houses with permanent lines, etc., fixed
plates are employed. Such plates need only be applied where the line is
always wet, or in workshops where the use of turntables is not of
frequent occurrence. This fixed plate is most useful in farmers'
stables, as it does not present any projection which might hurt the feet
of the cattle, and is easy to clean.

The only accident that can happen to the track is the breaking of a