24 Messrs. Faraday and Lyell on 



of the basin, it suddenly opens a passage into the mine for a 

 great quantity of air and gas, which before, by its relative 

 levity to the air, was retained in the goaf basin. Thus, as- 

 suming a goaf of 13 acres in a coal seam inclined 1 in 24?, and 

 that a fall of 6 feet in extent takes place in the roof at the 

 highest edge of the goaf, it would heighten the edge at that 

 spot 3 inches ; and if the goaf were full to the edge, either 

 with fire-damp or explosive mixture, these would flow out 

 more or less rapidly into the workings of the mine, until a ho- 

 rizontal stratum of 3 inches in thickness had thus escaped. 

 Even if the roof of the goaf rose very slowly, making an ex- 

 ceedingly flat dome, this stratum would extend to four-fifths 

 or more of the horizontal area of the goaf: and assuming that 

 the greater part of this space is occupied, not by gas, but by 

 the solid materials of the goaf, and that only a band round the 

 goaf could be considered as air space — still from what we saw 

 of the goafs at the Haswell Little Pit, this would be from 4 to 

 6 feet in horizontal extent, so that a mass of explosive atmo- 

 sphere or fire-damp might escape equal to a band about 3000 

 feet long, by 5 feet wide, and 3 inches deep, making about 

 3750 cubic feet. It is not likely that this would escape all at 

 once ; but the tenth, the twentieth, or the fiftieth part, or even 

 the hundredth part, would be enough to take fire at an injured 

 lamp, and to communicate fire to the whole, though the whole 

 condition between safety and danger up to that moment may 

 have depended upon 3 inches of the roof. 



The above is no hypothetical case, but must occasionally, 

 and as to the evolution of gas, frequently occur. If there be 

 gas in the mine, it is expected at the goaf: gas does come from 

 the goaf. All working at the goaf, except with safety lamps, 

 is forbidden : the seams in mines are usually more or less in- 

 clined ; and this mine at Haswell, where gas has come from the 

 goaf, is very free from gas, and well-ventilated, as compared 

 with other pits. 



There is one other point connected with what may be called 

 the action of the goaf, and the occasional sudden and tempo- 

 rary discharge of gas from it. One of the witnesses on the 

 inquest, Mr. G. Hunter, pointed out the effect he had ob- 

 served in the mine on a change in the barometer : — that as the 

 barometer tell, fire-damp would tend to appear, and that it 

 did this the more suddenly and abundantly, if the barometer, 

 having continued high for some time, fell suddenly : and Mr. 

 Buddie has already strongly stated his opinion that accidents 

 from fire-damp always occur with a low barometer. This is 

 very natural; for during a high barometer, the fire-damp, 

 tending to escape from the coal and strata, would be in some 



