To this elbow is attached a flexible pipe, E, 12 in. in diameter
and 25 ft. long, made of India-rubber, with a coil of iron inside
to help it to keep its shape. At the lower end of this pipe is an
elbow-shaped copper nozzle which rests on the bottom, and is fitted with
a grating to prevent stones getting into the pump and stopping the work.
The flexible tube is supported by chains that pass over the head of a
derrick, F, mounted at the stern of the dredger, and then round the
barrel of a steam winch. By this means the depth of the nozzle is
altered, as required to suit the depth of water.
A man stands at the winch, and lifts or lowers the pipe as is required,
judging by the character of the discharge from the pump. If the liquid
discharged is very dark and thick the nozzle is too deep in the sand
or gravel; if of a light color the pipe must be lowered. The best
proportion of water to sand is 5 to 1. When loose sand is the only
material to be dealt with, it can be easily sucked up, even if the
nozzle is deeply buried; but at other times stones interfere with the
work, and the man in charge of the flexible tube has to be very careful
as to the depth to which the nozzle may be buried in the sand.
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