COAL-MINING IN NEW SOUTH WALES. 1013 
The Greta or lowest group laps around an anticlinal dome of 
intrusive rock that occurs 27 miles north by west of Newcastle, 
and on its western side the Greta seam has been worked for many 
years. ‘This seam at its best has been found 18 feet thick, and 
yields a clean, hard, flaming, non-caking coal, unsurpassed for 
household use and somewhat singular in its characteristics. In 
one small part of Greta colliery this seam contained a shale parti- 
cularly rich in hydrocarbons. To the south and east of the anti- 
cline this seam has been opened up and, in places, found of great 
thickness and of excellent quality. Northwards its extension is 
unknown. 
The Rathluba series, separated from the Greta group by some 
800 to 1,000 feet of strata, and itself from 700 to 1,000 feet thick, 
contains various thin seains of coal which, although of a quality 
inferior to the Greta and the ‘ Borehole” seam of Newcastle, are 
worked toa limited extent in the neighbourhood of East Maitland. 
The Newcastle series overlies the Rathluba, with 1,000 feet of 
intervening strata, and is found cropping up in a line running 
north-west from the town of Newcastle for a distance of 16 miles, 
while to the south beyond the limits of the existing collieries its 
extension is ill-defined. 
Tn this series are found some eight or nine seams of coal, some 
of little present or prospective value, while others not now worked 
will become valuable in time to come. 
The lowest workable seam is the well-known “ Borehole” seam, 
which for purity and general usefulness occupies the premier 
position among Australian seams. The coal is strong, bright, and 
bituminous, excellent for household and gas-making purposes, and 
of good quality for steam-raising. Jt contains 36 per cent. of 
fixed carbon, 57 per cent. of volatile hydrocarbons, and 43 per 
cent. of fixed ash. In and around Newcastle this seam occurs 
under most favourable conditions for working, is from 5 to 15 feet 
thick, has a good roof and floor, and is free from explosive gas. 
To the south of Newcastle, on the shores of Lake Macquarie, 
the Pacific Colliery is working one of the upper seams, which, being 
‘thick and easily won, is able to compete at a lower price with the 
“Borehole” seam. Further south, and 16 miles from Newcastle, 
at Catherine Hill Bay, the Wallarah Company is working one of 
the thick upper coals whose identity is scarcely determined. 
THE SOUTHERN COALFIELD. 
Many years subsequent to the establishment of the Northern 
coal industry, the “ Bulli” seam was opened out at Mount Keira, 
on the side of the mountain range overlooking Wollongong, and 
at later periods one colliery after another was established in the 
district till now ten fully equipped collieries are in more or less 
active operation. 
