138 A TREATISE ON DREDGES AND DREDGING 



wide by 17 ft. 3 in. depth of hold. The hopper has a capacity of 

 1250 tons and is 50 ft. long by 33 ft. 10 in. wide at the top and 2:> it . 

 wide below. Fully laden, and carrying 50 tons of coal in the bunkers 

 and 5 tons of water in the boilers, the draft is 13.94 ft. The 

 mean speed attained on runs with and against the current was 

 8.2 knots. Installed in the hull are two compound engines placed 

 nearly amidship, which drives at will either the bucket chain, the 

 centrifugal pumps for the suction apparatus, or the two propelling 

 screws. The two engines together develop 1000 indicated horse- 

 power. They are supplied with steam by two ordinary return-tube 

 boilers, placed forward and built of steel under the Veritas rules for 

 a working pressure of 113.8 Ibs. per sq.in. The two together provide 

 a heating surface of 3444 sq.ft. The steam for the dynamo engine 

 and for the centrifugal circulating pump is also taken from these 

 boilers, which are fed by two Worthington pumps. There are also 

 eight steam winches which are used in maneuvering the craft. 

 The framing carrying the upper pinion for the dredging chain is 

 removable above the deck level. The forward legs are secured 

 to the sides of the well, while the rear legs rest on deck, which is 

 stiffened below by a strong beam running across the hull. The total 

 distance from the bottom of the hull to the top of the pinion framing 

 is 53.31 ft. 



The ladder frame is a built beam 88.58 ft. long and allows dredging 

 to be done in depths of 13.12 ft. to 32.81 ft. of water without shifting 

 the upper support of the ladder. The upper pinion is of square 

 section, and was cast in a single piece out of white iron. The lower 

 pinion is hexagonal, and is a steel casting. The buckets, of which 

 there are 32, have a capacity of 28 cu.ft. and have the back sides 

 and lips of cast steel, while the body is of steel plate. The links 

 are alternately steel castings of double T sections and steel plates. 

 They are provided with renewable bushing of manganese steel, 

 which can be readily replaced after wear. The bolts are also of 

 manganese steel, and have square heads. The bucket speed is 

 such as to bring 16 over the top pinion every minute. 



The transmission gear fitted to the main engines allows either 

 of them to be used for driving the chain, or each for running a 

 centrifugal suction pump. It is also possible to use one engine for 

 driving both screws, while the other runs one of the centrifugal 

 pumps. In the latter case one of the screws is driven by means of 

 gearing. The centrifugals are driven from the engine, but the dredg- 



