OSBORNE-WALLSEND COLLIERY. 



225 



switched on to the brancli horse track as required from one 

 end of a flat, while the full returns pass an automatic switch 

 on to the main track at the other end of the flat. 



At the surface the coal is lowered down the mountain side 

 to the screens a mile away, along two series of self-acting in- 

 clines, worked with circulating endless ropes. From the 

 screens, the coal is conveyed by locomotive along a private 



Fig. 143. 



railway line for 1 miles, to the South Coast line, and a mile 

 further on to the Woollongong basin, from which most of the 

 coal is shipped. The locomotive can only take up 12 empty 

 waggons at a time, as the up grade is too steep for it to draw- 

 more. On the self-acting incline, certain safety provisions have 

 been made in case of a break-away. On the up line, bobbins 

 are placed between the rails to catch the axle of a skip should 

 it go down hill instead of up. This bobbin consists of a bar of 



Fig. 144 Bobbin. 



iron through which a pin passses in such a manner that one 

 end is heavier than the other (Fig. 144). The consequence is 

 that the shorter end is raised up. The higher end, which has 

 a recess cut out to engage with the axle of the skip, is placed 

 pointing up hill. As the bar is free to move, the up-coming 

 skip simply depresses it when passing over, but the bar im- 

 mediately rights itself, and is ready for action as soon as the 



