hine. The vessel was fitted with a steam engine and
boiler for working and manipulating the pumps and the heavy side
chains for the guidance of the dredger. The engine was 70 h.p., and
the total cost of one dredger was L8000. The number of hands required
for working this sand-pump dredger was one captain, one engineer, one
stoker and four sailors. Each machine was capable of raising about
1300 tons of material per day, the engines working at 60 and the pump
at 180 revolutions per minute. The sand was delivered into barges
alongside the dredger. The cost of raising the material and depositing
it in barges was about 1d. per ton when the sand pumps were working,
but upon the year's work the cost was 2.4d. per cub. yd. for working
expenses and repairs, and 1.24d. per cub. yd. for interest and
depreciation at 10% upon the cost of the plant, making a total cost
for dredging of 3.64d. per cub. yd. The cost for transport was 3.588d.
per cub. yd., making a total cost for dredging and transport of
7.234d. per cub. yd. Dredging and transport on the same works by an
ordinary bucket dredger and barges cost 8.328d. per cub. yd.

Two of the largest and most successful instances of sand-pump dredgers
are the "Brancker" and the "G. B. Crow," belonging to the Mersey
Docks and Harbour Board. Mr A. G. Lyster gave particulars of the work
done by these dredgers in a paper read before the Engineering Congress
in 1899. They are each 320 ft. long, 47 ft. wide and 20.5 ft. deep,
the draught loaded being 16 ft. They are fitted with two centrifugal
pumps, each 6 ft. in diameter, with 36 in. suction and delivery pipes,
united into a 45 in. diameter pipe, hung by a ball and socket joint in
a trunnion, so as to work safely in a seaway when the waves are 10 ft.
high. The suction pipe is 76 ft. long and will dredge in 53 ft. of
water. The eight hoppers hold 3000 tons, equivalent when solid to 2000
cub. yds.; they can be filled in three-quarters of an hour and
discharged in five minutes. Mr Lyster stated that up to May 1899, the
quantity removed from bar and main-channel shoals amounted to
41,240,360 tons, giving a width of channel of 1500 ft. through the
bar, with a minimum depth of 27 ft. The cost of dredging on the bar by
the "G. B. Crow" during 1898, when 4,309,350 tons of material were
removed, was 0.61d. per ton for wages, supplies and repairs. These
figures include all direct wo