Up to the year 1877 dredgers were seldom made with buckets of a capacity exceeding 9 cub. ft., but since that time they have been gradually increased in capacity. In the dredger "Melbourne," constructed by Messrs William Simons & Co. to the design and specification of Messrs Coode, Son & Matthews, about the year 1886, the buckets had a capacity of 22 cub. ft., the dredger being capable of making 37 ft. of water. The driving power consists of two pairs of surface-condensing engines, each of 250 i.h.p., having cylinders 20 in. and 40 in. in diameter respectively, with a 30 in. stroke, the boiler pressure being 90 lb. per sq. in. The vessel is 200 ft. long by 36 ft. wide and 11 ft. 6 in. deep, and is driven by twin screw propellers. The gearing is arranged so that either pair of engines can be employed for dredging. The speed under steam is 7 knots, and in free-getting material 800 tons per hour can be dredged with ease. On one occasion the dredger loaded 400 tons in 20 minutes. The speed of the bucket chain is 83 lineal ft. per minute. The draught of the dredger in working trim is 7 ft. forward and 9 ft. aft. The efficiency of the machine, or the net work in raising materials compared with the power exerted in the cylinders, is about 25%. The dredged material is delivered into barges moored alongside. Contrasting favourably with former experience, the "Melbourne" worked for the first six months without a single breakage. She is fitted with very powerful mooring winches, a detail which is of great importance to ensure efficiency in working. The "St Austell" (Plate I. fig. 3), a powerful barge-loading dredger 195 ft. long by 35 ft. 6 in. beam by 13 ft. deep, fitted with twin-screw compound surface-condensing propelling engines of 1000 i.h.p., either set of engines being available for dredging, was constructed for H.M. Dockyard, Devonport, by Messrs Wm. Simons & Co. in 1896. This dredger loaded thirty-five 500-ton hopper barges in the week ending April 2, 1898, dredging 17,500 tons of material in the working time of 29 hours 5 minutes.