The wooden cogs are said to run about six months before renewal. Power is supplied by a compound marine engine, with surface-condenser, 22 by 42 in. The runner-bearing has a water-sleeve to keep the sand out, supplied by a small force-pump worked at 60-lb. suction, discharges at the bottom, and is driven at 225 rev. The centrifugal pump, made by the Morris Machine Co., Baldwinsville, N. The essential features of this dredge are as follows: J., on gravel, much of which carried stones as large as a man’s head. I am informed that this dredge worked continuously for nine months at Harrison, N. The chrome-steel liners are said to have lasted from six to nine months. The cutter and liners were the only parts liable to damage, and these were easily replaced with brief interruption of work. This was done with no bad breaks and few shut-downs. of discharge-pipe, gravel containing boulders up to 200 lb. worked for nearly four years at League Island, Philadelphia, where it sucked up, passed through the pump, and forced through 3,700 ft. The large dredge of the Henry Steers Contracting Co. In harbor-operations, much larger stones are handled by suction-dredges. in diameter are not frequently encountered. whereas there are few profitable gold-fields which can be considered dredgeable, in which stones more than 12 in. In suction gold-dredges, this diameter has not usually exceeded 10 or 12 in. In my opinion, all three causes of trouble may be remedied: the first, by making stronger the parts most liable to wear and breakage the second, by means for loosening the gravel at the intake and the third, by sufficiently increasing the diameter of the suction-pipe. The suction hydraulic gold dredges have failed from three special causes: excessive wear and frequent breakage of pump-shell, runners and liners inability to dredge compact gravel which would not readily move towards the intake and, most important of all, closing of the suction-pipe by stones too large to enter it. Repeated failures in attempts to work gold-bearing gravels by means of suction dredges have created the impression that this method is impracticable.
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