320 COALFIELDS AND COLLIERIES OE AUSTRALIA. 



ing. There are two seains worked in the Greta coal mea- 

 sures. The top seam is split in places. The East Greta col- 

 liery works the bottom Greta seam. The Heddoii Greta col- 

 liery works the top or main Greta seam. At Stanford Merthyr 

 they work the lower split of the top seam, which splits up 

 again deeper down. The Pelaw Main colliery works the 

 middle and the bottom of the top seam. At Hebburii they 

 work both the upper and lower split of the top seam. Aber- 

 main works the whole of the top seam. Aberdare and Aber- 

 dare Extended also work the top seam. 



The Greta coal yields from 40 to 42 per cent, of volatile 

 hydrocarbons, being the highest proportion of volatile hydro- 

 carbons that any of that class of coal contains in New South 

 Wales. 



The following quotation from Prof. T. W. E. David* will 

 be of interest : 



"At a spot about one and a half mile further to the east- 

 north-east, known as the 'Pinch/ there is a natural outcrop of 

 the Greta coal measures 011 the north-west side of the Wol- 

 lombi to Maitland road. In this neighbourhood, traces of a 

 vast pre-historic fire in the Greta Coal Measures are to be 

 noticed at intervals. It has extended beyond the 'Pinch* in a 

 westerly direction, and in a north-easterly direction it has 

 spread through Cessiiock along the outcrop to Pelaw Main and 

 Stanford Merthyr. It originated probably not far from Cess- 

 nock, in the 'brassy top.' Then it spread south-westerly and 

 north-easterly along the main seam. Between Abermain and 

 Hebburn, where the seam splits, it followed the lower, that is, 

 the main or middle seam, and kept along it to Pelaw Main and 

 Stanford Merthyr, near which the fire seems to have died out. 

 The fact that these splendid seams have been 011 fire in pre- 

 historic time, on a very large scale, is one which I should like 

 to impress very strongly on the proprietors and managers of 

 the collieries in this important coalfield. There can be little 

 doubt, in my opinion, that the fire, which has extended over a 

 total distance of fully fifteen miles, along the outcrop, resulted 

 from spontaneous combustion. So intense has been the heat of 

 this great fire that, as already mentioned in an earlier des- 

 cription of the sections in this locality, large areas of sand- 

 stone and shale have been actually smelted by the great heat, 

 and a rock has resulted closely resembling a volcanic lava, 

 such, as andesite or basalt; in fact, it was originally mapped 

 by me as volcanic ash and scoriae. . . . But the evidence 

 is of much wider significance, as a warning to colliery niana- 



*The Geology of the Hunter River Coal Measures, New 

 South Wales. By authority, 1907, p. 144, et seq. 



