194 



A TREATISE ON DREDGES AND DREDGING 



and could not be entirely opened, thus preventing the discharge 

 of the load. To avoid this the doors are placed on both sides of 

 the scow and the hoppers are inclined outwardly to facilitate the 

 descent of the materials, once the doors are open. 



Dumping scows are tied one behind another by long lines, form- 

 ing a tow composed of 3, 4 or 5, and towed to the dumping place 



FIG. 62. Dumping Scows used at Suez. 



by a tugboat. But this method of hauling is not always possible, 

 especially when the sea is rough, as the rolling of the various scows 

 will disarrange the lines, causing loss of time and often injuring the 

 scows. To avoid this, dumping scows are built in the shape of 

 any ordinary sea-going vessel and are self-propelling. In the con- 

 struction of the Suez Canal, in transporting material from the Canal 



FIG. 63. Dumping Scow for Shallow Water. 



prism to the dump at the Bitter Lakes, some self-propelling dumping 

 scows were used. They were provided with bottom doors, were 

 108 ft. long, with 23 ft. beam, carrying 160 cu.yds. of spoil and 

 drawing 5 ft. of water. They were fitted with twin screws and a 

 pair of cylinders placed end to end. The engines worked at high 

 pressure without a condenser, with a tubular boiler at 120 Ibs. 

 pressure, using only fresh water. Whether loaded or light they 



