322 COALFIELDS AND COLLIERIES OF AUSTRALIA. 



(3) The practice of building stopping's with small coal, 

 or other carbonaceous material, and timber is one which should 

 be discontinued entirely. These stoppings are usually put in 

 several feet thick, and this is conducive to heating. Such 

 a condition may eventiially give rise to a fire, the result of 

 spontaneous combustion. 



(4) Arrangements, where practicable, for an adequate sup- 

 ply of water, under pressure, in order to deal with an outbreak 

 of fire. 



(5) The necessity of regarding all the seams in the Greta 

 Measures of the South Maitland Coalfields as being liable to 

 spontaneous combustion. 



(6) The necessity of inspecting old workings. 



Mr. Y. D. Lewes determined the ignition points of various 

 kinds of coal as follows: Cannel coal, 370 degrees C. ; Hart- 

 leport coal, 408 degrees C. ; Lignite, 450 degrees C. ; Welsh 

 steam coal, 477 degrees C. Prof. David, commenting on this 

 writes : * 



" Now, as the Greta coal is essentially in places of a can- 

 iielly nature, passing here and there into true cannel, its low 

 ignition point would in itself render it liable to spontaneous 

 combustion. In the second place, comment has already been 

 made on the fact that the Greta seams, of all the coal seams 

 of New South Wales, are the most liable to 'perishing' towards 

 the outcrop. This is so marked that a thirty-foot thick Greta 

 seam is usually so perished at its actual outcrop as to show a 

 thickness of only an inch or two of earthy carbonaceous mate- 

 rial to represent the whole seam. The remainder has 

 been removed by weathering that is, by oxidation. 

 Neither the Tomago nor the Newcastle coal seams perish to- 

 wards their outcrops to the same extent as do the Greta 

 seams. The Greta seams are specially liable to oxidation, and 

 even in cases where the 'brassy tops' are not present, every pre- 

 caution against risks from spontaneous combustion should be 

 taken by mine managers." 



Greta Colliery. 



This colliery is famous for its numerous fires. It is now 

 abandoned, and the machinery taken away. The downcast 

 shaft and tunnel are sealed, grass is growing on the stopping 

 of the former, and the observation pipes are plugged with 

 wood. The waste heaps, mostly composed of material filled 

 out during the various fires, are still burning, and it is not 

 safe to walk en them for fear of sinking down into the hot 



*Op. Cit., p. 148. 



