92 A TREATISE ON DREDGES AND DREDGING 



the forward end of the dredge is a slot, through which the lower 

 section of the ladder, 36 ft. long and 7 ft. wide, descends. An endless 

 chain of buckets travels up and down the ladder, cutting away 

 the bottom wherever directed, and delivering the material to the 

 discharger on top of the tower. The upper section of the ladder 

 for this purpose is carried up to the top on an incline. A joint is 

 provided between the sections, so that the lower portion can be 

 raised and lowered. The upper section is 73 ft. 10 in. long. The 

 buckets are of f-in. steel, and have a capacity of 1 cu.m. each. 

 The links of the chain are If in. x 1 in. steel, and are 3 ft. long. 

 The shaft at the top of the tower, around which the chain and buckets 

 travel, is 14 in. in diameter. 



The chain is driven by double-cylinder engines, 16x24 in., 

 with 10-ft. driving pulley with 38-in. face. The dredge is anchored 

 by wooden spuds or heavy vertical beams, 25 in. diameter, with 

 1800 Ib. iron shoes upon their lower ends. These ends are lowered 

 to the bottom, and sinking through the earth anchor the machine 

 securely. Besides the main engine, there are several auxiliary 

 engines for working the spuds, raising the ladder, etc. 



The material as dredged and raised to the top of the tower is 

 emptied into the bell of one of a pair of iron chutes. These are pipes 

 3 ft. in diameter and 185 ft. long, which run far out on both sides 

 of the tower. Water is pumped into them along with the solid 

 material. Great banks of sand are built up by its operations. 



When Mr. W. P. Williams, Sr., examined this dredge in the 

 Panama Canal in 1889 under the French Administration, it was 

 running nineteen to twenty-one buckets per minute, three-fourths 

 full, three buckets to the cu.m. The expansion of material in buckets 

 was 30 per cent, occupying more volume in the buckets than in 

 bank. He estimated in twenty-four hours' work it would accomplish 

 4800 cu.m. 



He gives the average efficiency of this machine as follows: 



Soft sticky clay buckets not fully emptying at 



upper tumbler 3000 to 4000 cu.yds. per day 



Hard clay 4000 



Sand 5000 



The machine is under the complete control of the captain, who 

 is stationed on the bow of the machine. A system of wheels at his 

 hand connects with the different engines, namely, raising and lower- 



