14G COALFIELDS AND COLLIERIES OF AUSTRALIA. 



The main valve regulates the point of admission, release and 

 compression, while the expansion valve is a variable one, since 

 the point of cut-oft' can be varied, and this can be done while the 

 engine is running. The two blocks, E and F, are on a spindle 

 cut with both right and left hand threads, and by turning 

 this, the lap is altered by either bringing the blocks together 

 or separating them. If the blocks are brought closer to- 

 gether the cut-oft' will be later; if they are separated, then 

 the cut-off will be earlier. When E and F are close together 

 they are out of gear, and the cut-off is given by the main valve. 

 The two valves moving in opposite directions give a quicker 

 cut-off ; this decreases wire drawing. The spindle is turned 

 by means of the hand w T heel Gr, which has a square hole in its 

 boss for the spindle. The boss is encircled by a screw carry- 

 ing a pointer H, the movement of which represents the altered 

 expansion to the eye. 



Fig. 81. Meyer's Variable Expansion Gear 



According to Professor David, the top coal seam at Cre- 

 morne is 2850ft. below sea level. Assuming that the seam con- 

 tinues at the same angle, i.e., 110ft. per mile, then allowing for 

 soundings, if the seam outcrops below the ocean, it should 

 be met with about 18 miles east of Port Jackson heads. "It is 

 improbable, however, that the outcrop is nearer than ten miles, 

 or further than fifteen miles from the coast." The seam which 

 was split up at Balmain improves at they drive east. About 

 half-a-mile east of the shaft, the top coal is 2ft. Sin. thick, slate 

 1ft. lOin., and then the bottom coal 1ft. 4in. Now, at the end 

 of the winning, the seam is from 5ft. Gin. to 5ft. 9in. thick, the 

 coal getting thicker while the band is thinning out. At 1450 

 yards east, off Ballast Point, they have started to open out 

 on the longwall system, where the coal is 5ft. thick, with one 

 band. The two winnings are 8ft. wide, and 7ft. high. Until 

 work is sufficiently advanced for the endless rope system, all 

 haulage is done by horses. 



This colliery is being equipped for an eventual output of 

 2000 tons per diem. The skips, on reaching the surface, will 

 first be weighed, so as to ascertain the weight of roal for which 



