SCOURING AND SLUICING. 



277 



A further satisfactory effort was made by the same ship on 

 a material consisting of sand and gravel, with a nucleus of solid 

 cemented gravel. The cut was made apparently with no greater 

 difficulty than in the looser material, stones the size of cocoa- 

 nuts being washed out and driven down stream ; in this instance, 



about 10,000 cubic yards of 

 material were removed in 

 eight working days. 



The method of mooring 

 the ship is shown by Fig. 

 281. The vessel was backed 

 to the shoal, or bar, and 

 moored by the bow to an 

 anchor placed up stream, and 

 to anchors laid out on each 



DRAG CHAIN 

 FIG. 270. 



DRAG 

 FIG. 280. 



FIG. 281. 



quarter. The vessel having been trimmed by the stern to just 

 clear the bed of the river, the engines were started full speed 

 ahead. The generated current being driven away from the ship, 

 no injury could possibly occur from the stirred-up sand working 

 into the stern-tube or pumps ; and as the cut proceeded, the 

 vessel pivoting on the bow was slewed from side to side of the 

 intended channel by the rudder, and, as soon as a trench was 



