GRETA COLLIERY. 325 



advisability of using every endeavour to overcome them by 

 -direct attack, and the removal of the heated material to the 

 surface ; for, unless the stoppings are limited in number, small 

 in sectional area, and the pillars crushed, absolute extinction 

 of the heated material cannot reasonably be expected." 



A fire broke out on 5th December, 1900, resulting in the 

 loss of five lives. The district north and west of the down- 

 cast shaft had been largely worked, and were practically aban- 

 doned ; also a large area east and south of the main south level 

 had been worked. Of previous fires, six had occurred south of 

 the big jig, and one on the north side of the downcast shaft ; 

 the last, being due to a workman's carelessness,, was not a 

 true gob fire. The pit Avas sealed down on the 10th December, 

 19UO, and re-opened in April, 1901, but after eleven days -the 

 fresh air caused another outbreak. The fire caused heavy falls 

 of the roof. The action of the flames could be traced 011 the 

 coal over the same area as the falls, i.e., over a distance of 



The best way to attack an underground fire, when pos- 

 sible, is to fill it out. Sealing oft' is unsatisfactory, partly on 

 account of the slowness with which heat is conducted away 

 through the strata above and below;, and partly on account of 

 the difficulty in shutting off the air." Experiments carried out 

 by Dr. J. S/Haldane and Mr. Meachan* showed that air might 

 be so bad as to extinguish a lamp, and yet be nearly as effec- 

 tive as pure air in producing heat by slow oxidation. Air con- 

 taining IT per cent, of of oxygen will extinguish a lamp, but 

 the oxygen would have to be reduced to less than one per cent. 

 in order to really check heating. 



The sealing of the Greta colliery was carried out as fol- 

 lows : 



Bunion holes were cut in the solid rock of the shaft, 19ft. 

 from the surface. Hardwood buiitons, 12in. deep by 5in. wide, 

 were put in, across which hardwood planks 2in. thick were 

 laid. These planks were cut to the circle of the shaft, and 

 covered with several layers of brattice cloth. Above this was 

 placed 4ft. in depth of plastic clay, and the whole was covered 

 with water for a depth of two feet. In the centre of the scaf- 

 fold was a rectangular door with an eye bolt at each corner, 

 to which chains were attached. A wire rope connected the 

 chains to a windlass, which was used for lowering and rais- 

 ing the door. The sealings were completed as far as possible, 

 with the exception of the doors, and these were lowered into 

 position simultaneously. A wrought iron pipe, one inch in 



*Trans. Inst. Min. Eng., 1898, XYL., 457. 



