with a dip, and when the hopper was full the water ran
over in a steady stream on either side. The proportion of sand
delivered into the hopper was about 20% of the total capacity of the
pump. The dredger was constructed by Messrs Smit of Kinderdijk, near
Rotterdam. In the same discussion Mr A. A. Langley, then engineer to
the Great Eastern railway, gave particulars of a sand pump upon the
Bazin system, which had been used successfully at Lowestoft. The boat
was 60 ft. long by 20 ft. wide, and the pump was 2 ft. in diameter,
with a two-bladed disk. The discharge pipe was 12 in. in diameter. The
pump raised 400 tons of sand, gravel and stones per hour as a maximum
quantity, the average quantity being about 200 tons per hour. The
depth dredged was from 7 ft. to 25 ft. The pump was driven by a
double-cylinder engine, having cylinders of 9 in. diameter by 10 in.
stroke, and making 120 revolutions per minute. An important
improvement was made by fitting the working faces of the pump with
india-rubber, which was very successful and largely reduced the wear
and tear. The cost of the dredging at Lowestoft was given by Mr
Langley at 2d. per ton, including delivery 2 m. out at sea. The
quantity dredged was about 200,000 tons per annum.

One of the earliest pumps to be applied to dredging purposes was the
Woodford, which consisted of a horizontal disk with two or more arms
working in a case somewhat similar to the ordinary centrifugal pump.
The disk was keyed to a vertical shaft which was driven from above by
means of belts or other gear coupled to an ordinary portable engine.
The pump within rested on the ground; the suction pipe was so arranged
that water was drawn in with the sand or mud, the proportions being
regulated to suit the quality of the material. The discharge pipe was
rectangular and carried a vertical shaft, the whole apparatus being
adjustable to suit different depths of water. This arrangement was
very effective, and has been used on many works. Burt & Freeman's sand
pump, a modification of the Woodford pump, was used in the
construction of the Amsterdam Ship Canal, for which it was designed.
The excavations from the canal had to be deposited on the banks some
distance away from the dredgers, and after being raised by the
ordinary bucket dredger, instead of being discharged into the barges,
they were led into a vertical chamber on the top side o