I. — Pumping Plant.

The pumping plant comprises a compound steam-engine, a continuous-current generator, two electric motors and two high-lift ram-pumps.

(a) Engine. — The horizontal compound Robey engine has high-pressure and low-pressure cylinders, 18 inches and 30 inches in diameter respectively by 40 inches stroke and it develops 440 indicated horsepower, at 90 revolutions per minute and a steam-pressure of 100 pounds per square inch. The engine, with automatic trip expansion-gear to both cylinders, is fitted with a flywheel, 16 feet in diameter, grooved for 14 driving-ropes, each 1½l inches in diameter.

(b) Dynamo. — The Scott-and-Mountain six-pole generator is constructed for an output of 220,000 watts, or 400 amperes by 550 volts at the terminals, at an approximate speed of 400 revolutions per minute. The generator is fitted with a pulley, grooved for 14 driving-ropes, each 1½ inches in diameter.

(c) Main Switchboard. — The main switchboard consists of a marble panel fitted with the following instruments and switches — A double-pole quick-break lever-switch for a current of 500 amperes ; an automatic overload circuit-breaker suitable for a current of 500 amperes ; an ammeter to read to 500 amperes ; a volt-meter to read to 600 volts ; and a shunt-regulating switch and resistance.

(d) Cables. — The main cables, for conveying current from the generator-terminals to the main switchboard, and from the main switchboard at the Harry pit to the pump switchboard at the John Henry pit, a distance of 2,550 feet, consist of 4 overhead conductors of bare copper wile, each conductor being composed of 19 wires of No. 11 standard wire-gauge, and supported on poles with cross-arms, and earthenware insulators. Two cables, each 450 feet long, for conveying the current down the shaft to the pumps, are composed of 61 wires of No. 13 standard wire-gauge. having a sectional area of 4 square inches. These cables are insulated with vulcanised bitumen, served with jute and compound, protected by a double armouring of galvanized-steel wires, and finally covered with jute and compound.

(e) Main Pumps. — There are two main shaft-pumps, with rams 11 inches in diameter by 18 inches stroke, each capable of delivering 500 gallons per minute to a height of 400 feet, at an approximate speed of 28 revolutions per minute. The pumps are rope-driven by the motors.

(f) Electric Motors. — The Scott-and-Mountain multi-polar motors for driving the pumps are each constructed for an output of 120 effective horsepower, at 450 revolutions per minute by a current of 450 volts at the terminals. Each motor is fitted with 10 cotton driving-ropes, for transmitting the power to the pumps.

(g) Motor-room Switchboards. — Two switchboards are provided, one for each pump, each board consisting of a marble panel carrying the following instruments and switches — A double-pole main switch for a current of 200 amperes ; an automatic overload and no voltage circuit-breaker ; an ampere-meter to read to 200 amperes ; a volt-meter to read to 600 volts ; and a shunt-regulating switch and resistance, for varying the speed of the motors.

Two Scott-and-Mountain single-pole liquid-starting switches are provided for starting and stopping the electric motors.

II. — Coal-Cutting Plant.

The coal-cutting plant consists of 3 Goolden dynamos with an output of 36,000 watts each at 350 volts. These are driven by the Robey compound engine recently erected for driving the electric pumping plant.

At present, 5 coal-cutting machines of the Goolden bar-type are at work — 3 in the Harvey and 2 in the Hutton seam. One machine in each seam is driven by a 25 horsepower four-pole enclosed motor, and the others by 18 horsepower two-pole enclosed motors.

This plant was erected by the Electrical Coal-cutting Contract Corporation, and the cutting was done by that company at a fixed price per ton, but the plant was afterwards bought by the South Durham Coal Company.

In addition to the coal-cutting plant, the generating plant is also driving a three-throw pump, with 6 inches rams pumping about 100 gallons per minute from dip-workings against a head of 120 feet ; and a 4 inches Gwynne centrifugal pump is delivering about 130 gallons per minute against a head of 60 feet.