156 A TREATISE ON DREDGES AND DREDGING 



large drum of a reversible hoisting engine. The line can be eiilu r 

 of chains or steel wire cables, the latter being preferred, owing to 

 the lighter weight and less friction, which means less wear. 



The various engines necessary for the operation of the dipper 

 dredge are the main hoisting engine, the swinging engine, the 

 engine for the spuds, and an engine for the dynamo. The main 

 hoisting engine is usually of the double-cylinder, double-drum, 

 reversible type and is located on the main deck forward. The swing- 

 ing engine also is located forward and of the double-cylinder, double- 

 drum reversible type. The spuds can be operated by a single or two 

 separate engines, the former is preferred, but in very large dredges 



FIG. 45. Dipper Dredge of 6 cu.yds. Capacity. 



the two forward spuds are operated by a double-drum reversible 

 engine, and the aft spuds by a single-drum reversible engine, or all 

 the three or four spuds by a 3- or 4-drum reversible engine. 

 An engine is also required for the dynamos, since the dredge is 

 lighted by electricity and arc lamps are provided on deck so as to 

 dredge even at night. Steam for the various engines is provided 

 by a marine boiler located near the stern. Boiler, water tanks, 

 coal bunkers and some of the engines are placed ;ift so as to counter- 

 act the weight of boom with the heavy bucket when the dredge is in 

 operation, notwithstanding it is firmly fixed to the ground by means 

 of spuds. 



All the various dredging operations are controlled by a man who 



