STIRRING DREDGES 145 



power and hose for throwing powerful jets of water. The boiler 

 was 20 ft. long and 42 in. in diameter with two 14-in. flues and had a 

 nominal 25 H.P. The pump provided two jets thrown from 2-in. 

 nozzles, the water being conducted from the pumps to the desired 

 point through flexible 4J-in. 6-ply hose. By a special arrangement 

 the steam was guided by only one man. Although in this case the 

 excavator was used more properly for land work than for dredging, 

 yet the same device was applied one year later to stir up the material 

 at the bottom so as to easily enter the lower end of a suction tube 

 of a hydraulic dredge. 



For many years the liarbor of Swansea, whose bottom was com- 

 posed of fine sand and mud, was kept clean by means of the stirring 

 process. The machine employed was a powerful steam pump 

 mounted on a boat. At the beginning of the ebb tide the pump 

 was put in motion and the boat sailed along determined courses, 

 agitating the bottom, and the fine particles of the materials that 

 were very light floated in the water and were carried away by the 

 receding tide. The machine could work only a few hours a day 

 and by changing continuously the course of the boat, the harbor 

 was scoured in all directions and the bottom kept at a given level. 

 This method has now been abandoned and a powerful double ladder 

 dredge has been substituted, not only for cleaning the harbor, but 

 to deepen its bottom so as to accommodate vessels of larger capacity. 



Revolving Drums. Revolving drums or rollers have been used 

 to stir up the material and thus allow it to be carried away by the 

 velocity of water. One of these machines, called the "hedgehog/' 

 was used in Lincolnshire and is thus described by Mr. Ed. Cresy in 

 his Encyclopedia of Civil Engineering. 



The " hedgehog " in use for removing mud in rivers, or the accu- 

 mulation on the land side of sea-sluices; is cylindrical in its form, 

 like a garden roller. Around the outside are attached eight or more 

 longitudinal ribs, each of which is armed with as many spades 

 or hoes fixed in them firmly by bolts and screws. This cylinder 

 revolves on pivots in gudgeons in the side frame, which is made of 

 oak, and diagonally braced in front of the roller or the revolving 

 cylinder. The iron spades, 9 in. long and 4 in. wide, placed about 7 in. 

 apart at each end of the shaft, are attached to a strong chain, by 

 which it is moved. When used it is attached to the stern of a barge, 

 which in Lincolnshire is usually drawn by horses. Sometimes a 

 barge is moored at some distance from the mouth of the sluice to 



