MOUNT KEMBLA COLLIERY. 235- 



take, and allowing the return air from the workings to pass 

 into the upcast shaft through a dumb drift or airway that 

 commences at a point inbye from the furnace ; it then inclines 

 towards the shaft, which it enters at a, point sufficiently high 

 above the furnace to prevent the ignition of the firedamp. The 

 amount of ventilation produced by a furnace varies as the 

 square root of the difference in temperature of the intake and 

 upcast. It is a mistake to think that coal costs nothing be- 

 cause it is won in the mine that uses it ; for the coal could be 

 sold if not used ; therefore, it should be debited to the cost 

 of ventilation at the current market price. 



The Mount Kembla colliery owns an area of 8,700 acres r 

 of which about 1200 acres have been worked out. The output 

 is about 1100 tons per diem; but fell off during 1907. To- 

 wards the south, where the seam is thin, about 2ft. lOiii., the 

 coal is worked by the long wall system ; but where the seam 

 becomes thicker, the bord and pillar method is used. Rolls 

 occur in the seam, but are not so high as at some other col- 

 lieries in the district, so do not interfere to the same extent 

 in the direction of the roads, or with the shape and size of the 

 pillars. 



Oil from shale was first produced here in 1865, but oper- 

 ations ceased within about a year. In 1874 the property was 

 sold to the Mt. Kembla Coal and Oil Company, who worked 

 the shale for some ten years, and then left oft' owing to unre- 

 munerative returns. According to official figures, approxi- 

 mately 8711 tons of shale have been won from the Mount 

 Kembla deposits. 



The large coal is shipped from Port Konibla, seven miles 

 distant from the mine. Some smalls go to Sydney for use 

 at the Power House, and some coal is used locally for coking 

 purposes. Since the disaster they have had to work more of 

 the thinner portion of the seam. The coal won produces more 

 ash per ton than that obtained from the thicker portion ; also 

 the coal contains less bituminous matter, so requires greater 

 heat to coke it. 



Two types of coal-getting machines are employed at this 

 colliery, both driven by electricity. The Goodman chain 

 breast machine is used in the bords ; while Hurd's pick-quick 

 machine is employed for longwall work. The Goodman 

 variety of machine is that known as the "low vein," and is 

 only nineteen inches in extreme height; it is capable of giving 

 6ft. depth of undercut for a width of 3ft. 9in. It is prac 

 tically the "standard machine" modified for work in low 

 seams. The machine shown in Fig. 149 differs slightly from 

 that at work in the Mount Kembla mine, for the latter has 

 rollers on either side at the motor end, so that the machine 

 can be^ more readily shifted sideways for a fresh cut. The 

 motor is enclosed in a perfectly flame-proof cast-iron casing. 



