DREDGING FOR METALS 229 



the hull being especially trussed along the well-hole line with an 

 overhead structure. The bow gantry, supporting the digging ladder 

 and buckets, is of the most improved design, being constructed 

 to minimize working of the low pontoons. 



" The buckets, each of 5 cu.ft. capacity, are close connected, and 

 are provided with heavy manganese steel lips. Altogether there 

 are 82 buckets. 



"There are two winches on the boat, both located forward; 

 one on the port side, by means of which the digging ladder is raised 

 and lowered; the other on the starboard side, carrying the auxiliary 

 lines used in swinging the dredge from side to side. The digging 

 ladder is held up hard and fast to the face of the cut by means of 

 a steel spud 24 by 36 in. and 50 ft. long. A wooden spud is also 

 provided, of the same dimensions as the steel spud, and is chiefly 

 used to move the dredge forward after the bed rock has been cleaned 

 and a new cut is necessary. In this process, both spuds are alter- 

 nately raised and lowered, until the dredge has stepped ahead to 

 the position. 



"This machine is operated entirely by electricity. Electric 

 power is delivered at the dredge at approximately 4000 volts, being 

 carried aboard by armored cable at that voltage and stepped 

 down with transformers from 4000 volts to 400. The following 

 motor equipment is used: The digging motor is a 100 H.P. type F, 

 variable speed, operating, as all motors do, at 400 volts, and having 

 a speed of 600 R.P.M. It is connected by belt to the port winch, 

 which drives the bucket line, and lowers or raises the ladder. 



"The motor connected with the starboard winch by a belt 

 is of 20 H.P., type F, variable speed, having a speed of 900 R.P.M. 

 By means of this motor and winch, the wooden and steel spuds are 

 hoisted, the stacker raised and lowered, and the side and head lines 

 in handling the dredge controlled. 



"The 8-in. centrifugal pump is direct connected to a 50 H.P., 

 motor, type CCL, constant speed, having a speed of 850 R.P.M. 

 A 15 H.P. motor of the same type with a speed of 1120 R.P.M. is 

 direct connected to the 4-iii. centrifugal pump. 



"The revolving screen with a speed of approximately 8 R.P.M. 

 is operated by a belt from a 20 H.P., type CCL, constant speed 

 motor, having a speed of 1120 R.P.M., and connected by belt to 

 the drive of the conveyor. As stated, this is of the Robbins type, 

 equipped with a 30-in. special Diamond Dredge belt, the entire con- 



