ls a speed of 8-1/2 knots was
obtained. The bucket ladder, which weighs over 100 tons, exclusive of
dredgings, is raised and lowered by a set of independent engines. For
manoeuvring, powerful winches driven by independent engines are placed
at the bow and stern. The vessel is fitted throughout with electric
light, arc lamps being provided above the deck to enable dredging to
be carried on at night. Steam steering gear, a repairing shop, a
three-ton crane, and all the latest appliances are installed on board.

The "Derocheuse" (Plate II. fig. 12), constructed by Messrs Lobnitz &
Co., is a good example of the dredger fitted with their patent rock
cutters, as used on the Suez Canal. These rock cutters consist of
stamps passing down through the bottom of the dredger, slightly in
advance of the bucket chain, and are employed for breaking up rock in
front of the bucket ladder so that it may be raised by buckets
afterwards. This system of subaqueous rock cutting plant, on Messrs
Lobnitz's patent system, was effectively employed in deepening the
Manchester Ship Canal, and removed a considerable length of rock,
increasing the depth of water from 26 ft. to 28 ft. at a cost of about
9d. per cub. yd. A full and illustrated description of this plant, and
of a similar plant supplied to the Argentine Government, was published
in _Engineering_ of August 17, 1906. An illustration of a bucket of 54
cub. ft. capacity constructed by Messrs Lobnitz & Co. is given (Plate
II fig. 11), from which some idea of the size of dredging machinery as
developed in recent practice may be obtained. In regard to the depth
of water that can be obtained by dredging, it is interesting to note
that the dredger "Diver," constructed by Messrs. Hunter & English for
Mr Samuel Williams of London, is capable of working in 60 ft. of
water. In this vessel an ingenious arrangement was devised by Mr
Williams, by which part of the weight of the dredger was balanced
while the ladder itself could be drawn up through the bucket well and
placed upon the deck, enabling a long ladder to be used for a
comparatively short vessel. The "Tilbury" dredger, also constructed by
Messrs Hunter & English, was able to dredge to a depth of 45 ft. below
the surface of the water.

_Hopper Barges._--To receive the materials excavated by barge-loading
dredgers, steam hopper barges are now generally employed, capable of
carryin