,84 



COALFIELDS AND COLLIERIES OF AUSTRALIA. 



The General Electric Company have supplied a continuous 

 current generator of 240 amp. and 250 volts, driven by a com- 

 pound engine, and intended for haulage, but at present it is 

 used for lighting purposes and for driving a centrifugal pump. 



Newcastle A. and B. Pits. 



This colliery belongs to The Newcastle Coal Mining Com- 

 pi.ny Limited. Mr. J. Croft was manager for 19 years, but has 

 been succeeded by Mr. H. J. Thomas. 



The seam is from 3 to 10ft. thick. This is one of the only 

 two mines in the Newcastle district, where the longwall method 

 is worked ; but the pillar and bord method is also used where 

 the seam is thicker than, say, 5ft. In the longwall workings, the 

 roof settles gradually without cracking or bumping. It 

 settles down as a whole, first bending about 20ft. from the 



.Po.ce. ol- 



Fig. 184. Long Wall System. 



face, and finally settling about 50ft. from it. There are two 

 longwalls, one about 250yds., the other about 300yds., the 

 lengths being limited by local conditions. The main gate- 

 way is at right angles to the straght longwall face (Fig. 184) ; 

 cross gateways branch oif from either side of the main gate- 

 way at an angle of 45deg. towards the face, those on the same 

 side being 50yds. apart, but they junction with the main gate- 

 way alternately with those on the other side. Branching off 

 from the cross gateways on the coal side, and running parallel 

 with the main gateway, are gob roads placed 30yds. apart, 

 which help to shorten the distance the coal has to travel to 

 the shaft. Packwalls are built on either side of the gate- 

 ways, and are made 4ft. thick : chocks are built in every 

 4yds. These get squeezed together as they take up the 

 weight of the roof, so that a roof originally 5ft. Gin. high 



