C—3

46

Boilers. —The boilers are each 30ft. long, 7ft. in diameter, made of Siemens-Martin steel-plates ■fin. thick. Each boiler is to have two flues, 2ft. 9in. internal diameter, except the last two rings of plates at the back, the last plate to be 2ft. 3in. in diameter, the second plate from end to taper from 2ft. 3in. to 2ft. 9in. The plates for the flues to be of steel, |in. thick, welded longitudinally and flanged outwards at the ends. The end-plates of the boiler to be of steel, of same description as the shell, and to be in one plate J~|in. in thickness, and well stayed. The boilers are to carry a daily working-pressure of 1201b. to the square inch, and are to be fitted with Howl's patent hot-blast forced-draught furnace in each flue, having a grate Bft. long, and a secondary bridge 13ft. from the front plate, and to be fitted complete with all cocks, pipes, ha. Pumping-engines. —Consist of a pair of horizontal compound condensing engines, the cylinder of the high-pressure engine being 31in. internal diameter, and the low-pressure cylinder 59in. diameter, the stroke of the piston being sft. Steam-chests are to be fitted at each end of both highland low-pressure cylinders, and fitted with variable expansion-valves worked direct from crankshaft, variable by hand, the range of cut-off being from nothing to five-eighths stroke. The piston-rods are to be of forged steel and not less than sin. in diameter, and are to project through both ends of cylinders ; to be secured to front and hind cross-heads by steel cotters, having a solid collar forged on for attachment to piston, and to be screwed. The crank-shaft is to be of the best hammered steel turned and grooved where necessary; the bearings are to be 13-|in. in diameter and 20in. long. The shaft is to be swelled in the centre to 16in. diameter to receive fly-wheel and spur-pinion for driving pump gearing. The second motion shaft is to be fitted at the end of engine-bed for driving the mine pumps. It is to be of the best hammered steel, with bearings 20in. in diameter and 30in. long, three in number. The centre of the shaft is to be swelled to 22in. diameter to receive the spurwheel, which is to have seventy-six teeth, Bin. pitch, 21in. wide, and shrouded to pitch-line. The spur-pinion is to have nineteen teeth of same pitch and width, also shrouded to pitch-line. So that the speed of the pistons of the engines when the pumps are making eight strokes will be 320 ft. per minute. There are to be two cranks on the second motion shaft of the best hammered steel, 3ft. from centre to centre. The cranks are to be forged on the shaft and afterwards keyed with two keys not less than 3}in. wide and 2in. deep. The crank-pin"is also to be of hammered steel, with a bearing of 17in. in diameter and 22in. long. A shaft with two bearings, each 20in. in diameter and 30in. long, is to be fitted to the outer crank. This shaft is to be removed when the additional pumping-engine is added. .- Mine Pumps. —The pumps, rising-main, tanks, and spear-rods are to be suitable for raising 2,ooogals. of water per minute from a depth of 2,000 ft.; but at the present time one pair of pumping-engines are to be erected, and these will lift this quantity of water from a depth of I,oooft. It is proposed to raise the water from a depth of I,oooft. in three lifts, each of about 327 ft. vertical height, with two sets of pumps each, consisting of two plunger-pumps and one draw-lift, the plungers and buckets to be 25in. in diameter. The pumping-cranks to be so fixed that the pumps can be worked at either a 3ft., 4ft. 6in., or 6ft. stroke, as may be deemed necessary. The risingmain for the bucket-pump to be 26in. in diameter. "There is to be only one rising-main of 26in. internal diameter for the two plunger lifts, and, according to the specifications sent out from England, the mains are proposed to be constructed of steel lap-welded in lengths of 14ft. All necessary branches, bends, and connections to be of the same material. The joints in the mains are to have flanges riveted on to the pipes, and they are to be bolted together with steel bolts. The pipes are to be manufactured by Thomas Piggott and Co., of Birmingham, 'to be coated with Dr. Angus Smith's preparation, and to withstand a, hydraulic test pressure of 2501b. to the square inch without showing any signs of leakage. Stamp Mill to be driven by Electricity. —lt is proposed to drive a 40-head stamp-battery by electricity. The dynamo is to develop 55,000 volts at a speed of 700 revolutions per minute. The electro-motive force of the dynamo to be from 300 to 500 volts, according to the distance through which the power has to be transmitted to the stamp-mill. The motor to be similar in all respects to the dynamo, with the exception that there is to be no loose pulley and striking gear; and it is to give 68 brake horse-power at the motor shaft, with 55,000 volts at the terminals, at a speed of 650 revolutions per minute. All cables to be of suitable strength for carrying the current at not more than 1,000 amperes per square inch density. The dynamos are to be driven by the pumpingengines when these are working below their power. Electric Light Installation. —A steam-engine is provided capable of developing 10 brake horsepower when working at 1001b. per square inch. The dynamo is compound wound, of sufficient capacity for two 2,000-candle power arc lamps and seventy-five 16-candle power incandescent lamps, to run at about 1,250 to 1,350 revolutions per minute, having all necessary fittings and cable. Winding-engines. —The winding-engines are very small, and could hardly be termed adequate for winding a large quantity of material from even the depth of I,oooft. They have double cylinders, giving about 16-horse power, capable of winding a load of 30ewt., it is stated, at the rate of 333 ft. per minute. The winding-drums are sft. in diameter, having flanges 6ft. 3in. in diameter, the rope face of the drums being from 14in. to 15in. each, and they are to be worked by clutch in opposite directions. Each of them is fitted with complete brake of extra power, lined with wood. The steam for these engines is to be taken from the set of boilers already referred to. ■ . Air-compressor and Bock-drills. —The air-compressor is of the coupled compound type, the aircylinders being also compound. The air is compressed to a certain extent in one cylinder, thence passed through a cooler and reduced there to its original temperature, when it is further compressed in the other air-compressing cylinder to its final pressure; thence stored in the receiver. Engines. —The steam-engines for working the compressor are compound condensing, having cylinders of 16in: and 31in. in diameter respectively, the stroke of the piston being 3ft. The highpressure cylinder is to have an expansion-valve, with Meyer's or other suitable gear for working by hand, the range of cut-off being from nothing to five-eighths stroke; the working-pressure to be 1201b. per square inch, steam being taken from the range of boilers already referred to. The aircompressing cylinders are to be 19Jin. and 31in. in diameter, the stroke being 3ft., and are to be driven by back-rods from the engine cylinders.