238 



COALFIELDS AND COLLIERIES OF AUSTRALIA. 



ployed, especially when the face is long, and two or more 

 machines follow each other. AVhere the roof is strong there 

 is a temptation to increase the length of the face, so as to 

 reduce the cost of flitting per ton of output ; where the depth 

 of cut and thickness of seam yield a large output, the cost per 

 ton for flitting is very insignificant. When working the 

 machine to and fro, it has to wait before starting again till 

 the coal is cleared away. 



Three endless ropes pass into the main tunnel, one 

 in the middle and one on either side for two districts. Near 

 where the rails branch off, the side ropes pass through forks 

 which work the switches when struck by the clip attached to 

 the skips. The mechanism of this automatic arrangement 

 may be seen by referring to Fig. 152. A wrought-iron plate 



o 



TOT 



Fig. 1 52 Automatic Switch. 



(A) is bolted through the holes (B) to sleepers between the 

 rails. On this rest two bars (C), each having a triangular- 

 shaped head; the lateral motion of these bars is limited by the 

 staples (D) arranged near their ends. The two bars (C) 

 are connected by means of the lever (E), which is secured to 

 the plate (A) by the stud (E). on which it can turn. Studs 

 (Gr) are screwed into the bars (C), which fit into slots cut in 

 the lever (E). The fork (H) when struck by the clip, 

 pushes (C) forward and drops out of the way of the skip into 

 the rectangular hole (J) cut in the plate (A). The bar switch 

 {K) has two angle irons (L) secured to it for adjusting the 

 travel of the switch. The clippers-on, by attaching an 

 empty skip to the rope of the district for which it is in- 

 tended, are able to feed whichever district they desire from 

 the entrance of the tunnel, without further trouble; for when 



