THE METROPOLITAN COLLIERY. 149 



30 to 35 years' supply of coal opened up. Though still de- 

 veloping, it is not necessary to do so at the same rate as for- 

 merly, for every foot of headings driven represents a larger 

 spread of coftl. 



The two shafts are each 1100ft. deep, are circular in cross- 

 section, and are lined with brickwork where necessary. The 

 downcast shaft is 16ft. in diameter, and the upcast shaft 15ft. 

 in diameter. Although the shafts are 1100ft. deep, some of 

 the workings, partly owing to ridges on the surface, and partly 

 owing to dip workings, have 1500ft. of cover. These are the 

 deepest colliery Avorkings in New, South Wales if we except 

 the Sydney Harbour Colliery, which is scarcely in the produc- 

 ing stage yet. 



The Bulli seam in this colliery is about lift, thick. Only 

 some 6ft. Gin. of the upper coal which is free from partings is 

 worked, though the lower coal is taken up in the headings. 

 This is good steam coal; though jointy, it is closer in grain, 

 harder, and higher in fixed carbon than that from the same 

 seam with less cover worked further down the coast. On 

 account of the jointy nature of the coal, it is so easily won 

 that less men are required for the same output than at most 

 other coal mines. 



All the hoisting and travelling is done in the downcast 

 shaft, where the winding engine lifts a total load of seVen 

 tons, including cages, chains, load and rope from cage at 

 bottom to pulleys, 1100ft. in 28 seconds ; another 7 to 8 seconds 

 being required to discharge loaded skips and replace with 

 empties. The engine is capable of raising 1600 tons of coal in 

 eight hours, but the actual work accomplished has been 1500 

 tons during that period. The winding engine has 34in. dia- 

 meter cylinders, and 5ft. 6in. stroke. It has double beat Cor- 

 nish valves and trip gear. The drums, which are placed 

 parallel, are 15ft. in diameter. The cages carry two skips each, 

 which are placed tandem ways, and held on the cages by stops; 

 when the latter are depressed, the on-coming skips are made to 

 push out those already in the cage, and take their places. The 

 guides are made of ropes consisting of six fin. iron rods twisted 

 together, so that the whole is IJin. in diamefer. There are 

 three of these guides for each cage, two placed on the side 

 nearest the wall of the shaft, the other near the 

 middle of the opposite side, but not exactly opposite 

 the corresponding rope of the other cage (Fig. 85). 

 They are fixed at the top by passing the end of 

 each rope through a hole in a girder, doubling it over, and 

 clamping with three clamps (Fig. 83). At the bottom, the 

 guides are doubled through eye-bolts that hang loose in the 

 shaft, and are clamped in a similar manner as on the pit-head 



