shaft, which
passes down the center of the post, and by means of a cross shaft is
geared to the front axle, from which four of the ground wheels are
driven.

The post is octagonal, built up of plates 3/4 in. thick; at the bottom
end it is secured to the girders of the truck, and at the top is
shrunk on to a large gudgeon 12 in. in diameter, which enters a
casting fixed in the back end of the jib; on the top of the gudgeon
are two steel disks on which an adjustable cap rests; by means of this
and the ties to the tail and the lower end of the strut a proportion
of the weight can be brought on to the post so as to relieve the
roller path to any desired extent, and enable the crane to be revolved
easily.

The truck is 24 ft. long and 16 ft. 41/2 in. wide; it is constructed of
longitudinal and transverse box girders 2 ft. 8 in. deep, and rests on
two axles 6 in. in diameter; round these axles swivel the cast-iron
bogie frames which carry the ground wheels. This arrangement was
adopted because the crane has to travel up a gradient of 1 in 30, and
the bogies enable it to take the incline better; they also distribute
the weight more evenly on the wheels. The gauge of the rails is 15 ft,
the wheels are 2 ft. 6 in. in diameter, and have heavy steel tires.
The weight on each of the front wheels when running with the ballast,
but no load, is about 16 tons. A powerful brake is applied to the
wheels when descending the incline.

All the clutch levers, break treadle, and handles are brought
together, so that one man has the crane under his entire control. An
iron house, of which the framing only is shown, extends from the
gearing right back to the boiler, forming a most spacious engine room
and stokehole. A separate donkey engine is provided for feeding the
boiler. The truck is furnished with legs under which packings can be
wedged so as to relieve the load on the wheels when block-setting. The
slings seen under the boiler are for hanging a concrete balance
weight; this will weigh about 20 tons. The weight of the crane itself
without load or ballast is about 80 tons. The crane was tested under
steam with a load of 19 tons with the most satisfactory results; the
whole machine appeared to be very rigid, an end often very difficult
to obtain with portable wrought-iron structures and live loads. The
result in the present case is probably greatly due to the careful
workmanship, and to the fact that the sides and ends of the plates are