292 COALFIELDS AND COLLIERIES OF AUSTRALIA. 



of the seuin, and adjacent rocks, causes the overlying strata. 

 to bear more heavily on the pillars that are left. When rock 

 is broken up to, say, the size of road metal, it occupies about 

 one-third more space than it did before it became broken up. 

 At first one might think that it would be a simple matter to 

 calculate at what height a crush of a certain amplitude would 

 cease to aftect the overlying strata. But those accustomed to 

 mining operations are aware that though some of the roof 

 may break up into slabs, and comparatively small pieces, the 

 rock overhead comes down in large bodies, consequently the 

 effect of a crush may be far-reaching. 



The main and tail rope system of haulage is used in the 

 mine, a set of skips travelling at the rate of 8 miles an hour. 

 The driving engine is one of Tangye's duplex engines, with 

 Cornish valves, 32in. diameter cylinders, 4ft. stroke, and the 

 drums are 6ft. in diameter. To guide the rope on to the 

 drum, there is a lever, with a sheave at one end ; while at the 

 other is a cord manipulated by the driver. 



At the bottom of the shaft are four double SJin. cylinder 

 Worthiiigton pumps, and a Tangye pump with a 12in. work- 

 ing barrel and a 4ft. stroke, worked by steam conveyed from 

 the surface; the exhaust escapes up the fan shaft. 



The fan is a 13Jft. Schiele, with blades 4ft. wide, which 

 revolves 120 tim.es per minute; it is belt driven from a 

 Walker's engine, of which there is a spare duplicate. The 

 overcasts are made of wood, the joints are cemented over, and 

 the whole covered with a layer of Sin. of sand as a protection, 

 in case of fire. 



There are two ambulance cabins below, which contain 

 stretchers and a box of first-aid appliances. 



The men and liorses enter the mine down a slope cut in 

 the rock at an angle of one in six. 



The winding engine is on the first motion, and was built 

 by the Grange Iron Co., Durham, England. The cylinders 

 are 26in. diameter, the stroke 4ft., and the drums 8ft. Sin. 

 in diameter. The valves are of the Cornish type. Band 

 brakes are arranged on the outside edge of the drum, but 

 there are also steam brakes. There is a white mark on the- 

 top of the cage, and also on the side of the shaft frame, so 

 that drivers can see when the cage is in the proper position at 

 the surface. Side rail guides are fixed in the shaft. They 

 have a butt joint, and are kept in position by a stretcher 

 plate bolted to the Imntons, and clips 1o hold the rails are 

 bolted to the stretcher plate and bunton. A Walker's safety 

 hook, for a load of 4 tons, is used in case of over-winding. 

 This hook differs from most other safety hooks in principle, 

 inasmuch as with the Walker hook the 'load tends the whole 

 time to cause detachment, but is prevented from doing so by 



