326 COALFIELDS AND COLLIERIES OF AUSTRALIA. 



diameter, was carried for six feet below and through the seal- 

 ings to the surface, for observation purposes. 



The opening at the tunnel was sealed with two brick stop- 

 pings nine inches thick, between which eight feet of sand, 

 was placed and well rammed in. The roof, side and floor were 

 cut to a solid foundation, to allow a tight joint to be made 

 with the brickwork. There was no door in the tunnel stop- 

 ping. The stopping was not built too strong, as it was to b& 

 pulled down again at a later stage. 



After some months, the sealings were removed, and the 

 heated material filled out, but it had to be cooled first with 

 water. The sides of the pillars were found to be incandes- 

 cent to a depth of four feet, so an iron bar was driven into the 

 pillars for this depth, and the nozzle of a hose inserted. This 

 method of cooling proved very effective. Where large pieces of 

 "brassy tops" hud been under water for weeks, and the water 

 subsequently drawn oft', it immediately commenced to heat y 

 some of it actually breaking into flame. This proves that a tem- 

 porary flooding of the mine was no good. If unsealed too soon, 

 though the flame may have been suppressed, and the external 

 portion of the heated matter cooled down, the internal parts 

 of the mass still remain heated, and only await the necessary 

 supply of oxygen for active combustion to develop again. The 

 process of cooling is very slow under non-conductive material 

 such as sandstone and conglomerate. The occurrence of large 

 falls of roof brought about a state of affairs favourable to spon- 

 taneous fires, as these falls covered up the brassy tops and 

 placed them outside the action of ventilation currents, while 

 at the same time there is sufficient oxygen present to cause 

 oxidation of the pyrites. Since the conglomerate falls in large 

 pieces, it adds to the trouble of filling out the "brassy tops,"" 

 for it has to be broken up smaller before it can be handled, 

 Mr. Jeffries further remarks* that, "Careful observation points- 

 to the fact that when the 'brassy tops' remain uncovered by 

 falls of stone or by the fine sand already referred to, no trouble 

 is experienced; but in cases where blanketing or covering oc- 

 curs with substances of low conductivity, trouble will almost 

 certainly occur." 



Jeffries recommends working the seam in panels, forming 

 the pillars where permissible to the rise and dip of the seam. 

 Also to work the pillars and brassy tops together ; and when 

 once the pillars are attacked, to extract them as quickly as 

 possible. 



Irregular work due to labour trouble would be liable to 

 cause great loss in working such a seam, not only to the col- 



. Cit., p. 532. 



