wide and 11 ft. 6 in. deep, and is driven by twin screw
propellers. The gearing is arranged so that either pair of engines can
be employed for dredging. The speed under steam is 7 knots, and in
free-getting material 800 tons per hour can be dredged with ease. On
one occasion the dredger loaded 400 tons in 20 minutes. The speed of
the bucket chain is 83 lineal ft. per minute. The draught of the
dredger in working trim is 7 ft. forward and 9 ft. aft. The efficiency
of the machine, or the net work in raising materials compared with the
power exerted in the cylinders, is about 25%. The dredged material is
delivered into barges moored alongside. Contrasting favourably with
former experience, the "Melbourne" worked for the first six months
without a single breakage. She is fitted with very powerful mooring
winches, a detail which is of great importance to ensure efficiency in
working.

The "St Austell" (Plate I. fig. 3), a powerful barge-loading dredger
195 ft. long by 35 ft. 6 in. beam by 13 ft. deep, fitted with
twin-screw compound surface-condensing propelling engines of 1000
i.h.p., either set of engines being available for dredging, was
constructed for H.M. Dockyard, Devonport, by Messrs Wm. Simons & Co.
in 1896. This dredger loaded thirty-five 500-ton hopper barges in the
week ending April 2, 1898, dredging 17,500 tons of material in the
working time of 29 hours 5 minutes.

An instance of a still larger and more powerful dredger is the
"Develant," constructed by Messrs Wm. Simons & Co., for Nicolaiev,
South Russia. She is a bow-well, barge-loading, bucket ladder dredger,
with a length of 186 ft., a breadth, moulded, of 36 ft., and a depth,
moulded, of 13 ft. The bucket ladder is of sufficient length to dredge
36 ft. below the water level. The buckets are exceptionally large,
each having a capacity of 36 cub. ft., or fully two tons weight of
material, giving a lifting capacity of 1890 tons per hour. At the
dredging trials 2000 tons of spoil were lifted in one hour with an
expenditure of 250 i.h.p. The propelling power is supplied by one pair
of compound surface-condensing marine engines of 850 i.h.p., having
two cylindrical boilers constructed for a working pressure of 120 lb.
per sq. in. Each boiler is capable of supplying steam to either the
propelling or dredging machinery, thus allowing the vessel to always
have a boiler in reserve. On the tria