300 COALFIELDS AND COLLIERIES OF AUSTRALIA. 



The Guibal fan is 30ft. in diameter, and 10ft. wide. It 

 is given 50 revolutions per minute. This is driven by an 

 -engine, built by J. S. Rodgers, of Newcastle, N.S.AV., which 

 has a 20in. diameter cylinder. 



Tallow is burnt in the small lamps used in the working 

 places. 



For testing the thickness of the rock overhead, between 

 the seam and the ocean, they use a Diamond Drill Co.'s 

 double-handed machine (Fig. 194), but instead of a bit set 

 with diamonds, they either use an auger or a serrated steel bit, 

 "which gives a core. The core bit is only used for hard ground, 



Fig. 194. Rock Drill. 



;and for the last few feet of boring: the gear, regulating the 

 feed, can be changed as desired. A hand-pump is used to 

 pump the necessary water up through the drill. This machine 

 can be easily taken to pieces for convenient handling in con- 

 fined places. Originally this make of drill had the rods 

 coupled direct to the lower end of the spindle ; now they are 

 jnade with the spindle or screw shaft of such a diameter as to 



