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 working costs and a proportion of the charge for actual superintendence, but no allowance for interest on capital cost or depreciation. On an average, 20% of the sand and mud that are raised escapes over the side of the vessel. Mr Lyster has, however, to a considerable extent overcome this difficulty by a special arrangement added to the hoppers (see _Proc. Inst. C.E._ vol. 188).