38 COALFIELDS AND COLLIERIES OF AUSTRALIA. 



lieries the distance apart is greater. It is cleaner than fork- 

 filled coal, as the slack has a better opportunity of being 

 separated. Lump coal is better for transport, for although it 

 breaks up to a certain extent during handling, still the pro- 

 portion of fine coal is not excessive. Lump coal has to be 

 broken up before being used, and in so doing a certain amount 

 of small coal is produced, so some users prefer unscreened, as 

 not only being cheaper, but saving time and trouble in break- 

 ing up the lumps. Slack, small, or fine coal are synonymous 

 terms for coal that passes through the screens. Nuts is a 

 name given to coal that passes between screen bars fin. apart, 

 and oven screens with 3-16in. mesh; it is chiefly made for 

 mechanical stokers. "Duff" is the coal that is left after the 

 separation of the large coal and nuts; it is largely used at 

 some collieries for converting into coke. Bunker coal may be 

 unscreened, but more often it is small. 



