f the pump,
suitable arrangements being made for regulating the delivery. The pump
was 3-1/2 ft. in diameter, and made about 230 revolutions per minute.
The water was drawn up on the bottom side and mixed with the
descending mud on the top side, and the two were discharged into a
pipe 15 in. in diameter. The discharge pipe was a special feature, and
consisted of a series of wooden pipes jointed together with leather
hinges and floated on buoys from the dredger to the bank. In some
cases this pipe was 300 yds. long, and discharged the material 8 ft.
above the water level. Each dredger and pump was capable of
discharging an average of 1500 cub. yds. per day of 12 hours.
Schmidt's sand pump is claimed to be an improvement on the Burt &
Freeman pump. It consists of a revolving wheel 6 ft. in diameter, with
cutters revolving under a hood which just allows the water to pass
underneath. To the top side of the hood a 20 in. suction pipe from an
ordinary centrifugal pump is attached. The pump is driven by two 16
in. by 20 in. cylinders, at 134 revolutions per minute, the boiler
pressure being 95 lb. per sq. in. This apparatus is capable of
excavating sticky blue clayey mud, and will deliver the material at
500 to 650 yds. distance. The best results are obtained when the
mixture of mud and water is as 1 to 6.5. The average quantity
excavated per diem by the apparatus is 1300 cub. yds., the maximum
quantity being 2500 cub. yds.

Kennard's sand pump is entirely different from the pumps already
described, and is a direct application of the ordinary lift pump. A
wrought iron box has a suction pipe fitted at the bottom, rising about
half way up the inside of the box; on the top of the box is fitted the
actual pump and the flap valves. The apparatus is lowered by chains,
and the pump lowered from above. As soon as the box is filled with
sand it is raised, the catches holding up the bottom released, and the
contents discharged into a punt.

Sand-pump dredgers, designed and arranged by Mr Darnton Hutton, were
extensively used on the Amsterdam Ship Canal. A centrifugal pump with
a fan 4 ft. in diameter was employed, the suction and delivery pipes,
each 18 in. in diameter, being attached to an open wrought-iron
framework. The machine was suspended between guides fixed to the end
of the vessel, which was fitted with tackle for raising, lowering and
adjusting the mac