It will be noticed that since the rudder, if placed in its accustomed place in the centre line of the hull, would be in the way, it has been duplicated and placed on either side of the stern. After the dredger has taken aboard her full cargo of mud from the sea-bottom she proceeds to the deep sea, and there discharges her contents through doors placed in the bottom of the hull, though sometimes she may discharge the mud into barges brought alongside. It will be seen that the _Peluse_ has been very efficiently protected against any damage which might be inflicted by another vessel coming alongside her. These vessels are given very powerful machinery, which drives both the propellers and the dredging apparatus, an arrangement allowing the latter to be connected with the main engines. The most modern example of this type has triple-expansion engines and twin-screws, so that she is entitled to more respect than her unwelcome appearance might suggest. [Illustration: THE PADDLE-TUG “DROMEDARY.” _From the Model in the Victoria and Albert Museum._] [Illustration: THE BUCKET-DREDGER “PELUSE.” _From a Photograph. By permission of Messrs. Lobnitz & Co., Ltd._] The suction-dredger, on the other hand, as its name signifies, does not scoop up the sand, but sucks it up into her holds through pipes which reach down to the bed of the river or estuary. The largest of these is well-named, and is illustrated opposite page 242. This represents the _Leviathan_, which is owned by the Mersey Docks and Harbour Board, Liverpool, and it is through her work that the river is able to be maintained in a navigable condition. This voracious animal sucks up sand at the rate of 10,000 tons in less than an hour, by means of centrifugal pumps, and when loaded with this heavy cargo steams out to sea at a speed of ten knots, and then by means of doors discharges the sand through her bottom. The doors are worked by means of hydraulic machinery. She herself is propelled by four sets of triple-expansion engines, which also work the centrifugal pumps. We can get some idea of the size of this dredger when we remark that her enormous length of 500 feet makes her as long as the _Etruria_.