114 A TREATISE ON DREDGES AND DREDGING 



machinery, and all stoppages for repairs and other contingencies. 

 This cost would be greatly reduced in case the pump could work 

 continuously, discharging directly to the dumping ground through 

 either open troughs or pipes. 



The following description of the dredge "Thomas," used by the 

 Metropolitan Dredging Co. of New York, taken from Engineering 

 News, Vol. XLV, iUustrates a type of hydraulic dredge with two 

 rows of parallel hoppers and a single suction pipe located in a well 

 amidship. See Figs. 31 and 32. 



This dredge is of 7000 tons displacement, 300 ft. long, 52 ft. 

 6 in. beam, 25 ft. molded depth, and has a hopper capacity of 2800 

 cu.yds. of material and a speed of 10 knots. As will be seen from 

 the general plans, the hulls are of steel, and are provided with two 

 decks. For about 125 ft. amidships the hull space below the main 

 deck is taken up by a row of hoppers on each side, there being six 

 hoppers in each row, two being 22J ft. long by 18 ft. wide, and four 

 being 20 ft. long by 18 ft. wide. The forward portion of the space 

 between the two rows of hoppers is occupied by the well for the 

 suction pipe. Aft of the hoppers the hull space below the main 

 deck is given up to the main engine and boiler-room, propelling 

 machinery and steering gear, and forward the corresponding 

 space is devoted to the pump and pumping engines. The space 

 between the main and upper decks is devoted chiefly to the quarters 

 for the officers and men. The upper deck carries the derricks, 

 windlasses and usual above-deck structures of a sea-going vessel. 

 Taking up the description of the various parts named in more detail, 

 we have first to consider the dredging machinery and hoppers. 



The space forward of the hoppers, which is devoted to the dredging 

 machinery, extends the full width of the vessel and for 50 ft. fore 

 and aft. The main centrifugal pump is located in the center close 

 to the forward end of the suction pipe well. It is a 48-in. pump 

 built by the Morris Machine Works, of Baldwins ville, N. Y., and 

 has two side pipes to the suction pipe and two discharge openings 

 connected with separate discharge pipes leading to the two rows of 

 hoppers, as shown by the drawings. This pump is operated by 1 w<> 

 tandem, compound 17X30X36-in. stroke cylinder engines, exhaust- 

 ing into condensers. The pump has a guaranteed capacity of 75,000 

 gallons of water per minute, and will operate under a resistance 

 equal to about 40 ft. head of water. The centrifugal pumping 

 engines are placed forward of the pinup, and forward of them is a 



