140 



JVA TURE 



[Dec. 10, 1885 



air due to the presence of different proportions of fire-damp 

 have been made the basis of other gas-indicating apparatus ; a 

 test-lamp has been constructed to furnish a flame when burning 

 alcohol, which is much more sensitive than I he oil flame of an 

 ordinary safety lamp ; and an eJectro-photometric test apparatus 

 has been devised by Mr. E. H. Liveing, which appears to have 

 been the most thoroughly practical form of gas-indicator shown 

 at the recent Exhibition. 



The importance of being able to recognise very small 

 proportions of fire-damp in air has become specially evident, 

 since the fact has become thoroughly established, by recent 

 careful and comprehensive investigation, that when fire-damp 

 is present in the atmosphere of a mine, in proportions greatly 

 below those necessary to produce a feebly explosive, or even 

 barely inflammable mixture, it may yet constitute a most 

 formidable souice of danger, by its co-operation with the dust 

 which exists, in more or less abundance, in every mine-working. 



The fact that coal-dust adds considerably to the disastrous 

 effects of fire-damp explosions, was noticed already more than 

 80 years ago ; but Faraday and Lyell were the first to 

 demonstrate, forty years ago, how important a part might be 

 played by coal-dust, in aggravating and extending the destructive 

 effects of fire-damp explosions. When investigating a serious 

 explosion which occurred in the Haswell Colliery in 1844, they 

 observed many signs of the coal-dust being partly burned, and 

 partly subjected to a charring or coking action, by the fire-damp 

 explosion. Their lucid published account of the evidence that 

 coal-dust may play an important part in the effects produced by 

 mine-explosions covers much of the ground gone over by recent 

 workers and writers on the subject, and affords a curious illus- 

 tration of the ease with which the work of the most illustrious 

 men may be overlooked or forgotten, even by tho^e who should 

 be specially interested in informing themselves of the existing 

 state of knowledge on the subject. Thus, several well-known 

 French mining engineers published, many years after Faraday 

 and Lyell's work, observations, as new, which were simply 

 confirmatory of those philosophers' original statements and 

 conclusions. 



Messrs. Galloway and Friere Marreco, but especially the 

 former, have added importantly to our knowledge of the pro- 

 bable behaviour of dust in mines on the occasion of explosions. 

 Mr. Galloway, who performed experiments upon a considerably 

 larger scale than had previously been the case, was certainly the 

 first to enunciate the conclusion that a small proportion of fire- 

 damp is essential to impart to a mixture of air and coal-dust the 

 power of propagating flame, though he afterwards concluded 

 that fire-damp is altogether unnecessary for the conveyance of 

 flame, with explosive effects, by a mixture of dry coal-dust 

 and air. 



The more recent results of other workers in this direction 

 have, however, conclusively demonstrated that while some very 

 highly inflammable coal-dusts may, when raised and mixed with 

 the air by the force of a blown-out shot, become inflamed, and 

 carry flame to considerable distances, with a rapidity and 

 violence of action similar to that of a fire-damp explosion, the 

 extent to which flame is propagated, by most descriptions of coal- 

 dust, in the complete absence of fire-damp, is very limited. 



In a series of experiments which, after the calamitous accident 

 in Seaham Colliery in the autumn of 1880, I was requested by 

 the present Home Secretary to carry out with coal-dusts, it was 

 conclusively established that the proportion of fire-damp re- 

 quired to be present in the air of a mine, to bring dust readily 

 into operation as an explosive agent, when thickly suspended in 

 the air, may be even decidedly below the smallest amount which 

 a practised eye can detect by means of a Davy lamp. Various 

 other points of interest were established by this series of 

 experiments. 



The more extensive experiments subsequently made by the 

 Commission, in large mine galleries, demonstrated that with a 

 very highly inflammable dust suspended in the air in which no 

 trace of hydrocarbon gas was present, a blown-out shot could 

 produce ignitions which would extend as far as the mixture of 

 air with suflicient dust to maintain flame extended. 



Important experiments upon a very large scale, which have 

 recently been carried out by the Prussian Fire-damp Commis- 

 sion, at Neunkirchen, in the -Saarbrucken district (see Natuke, 

 vol. xxxi. p. 12, and vol. x.Kxii. p. 55), have thoroughly con- 

 firmed and also considerably extended these results. 



It appears now to be well established that the considerable 

 volume of flame and rush of gas produced by a blown-out shot is 



indispensable to the attainment with certainty of any of the 

 dangerous effects of coal-dust. Inasmuch, however, as blown- 

 out shot are of very common occurrence in blasting operations, 

 it is evident that in dusty mines there is a frequent liability to 

 the production of a more or less extensive ignition or explosion 

 of coal-dust, at any rate when even only very small proportions 

 of fire-damp exist in the air of the mine. It will be seen, there- 

 fore, that it needs not a sudden outburst or accidental liberation 

 of fire-damp in considerable quantities to cause the flame which 

 may be projected into the air by the firing of a powder-shot to 

 bring about extensive explosions, or ignitions, spreading over 

 large areas, and possibly communicating to distant accumula- 

 tions of explosive mixtures of gas and air in old workings. 



These most serious dangers, arising chiefly from the use of 

 powder in coal mines, have received the anxious attention of the 

 Commissioners, who have, in the first place, considered how far 

 it might be practicable to prescribe effectual means for removing 

 or counteracting the elements of danger presented by the exist- 

 ence of dust accumulations in mines where it may be impossible 

 to guard against the distribution of small proportions of fire- 

 damp through the air. 



The possible substitution for gunpowder of other explosive 

 agents which may be applicable to the kind of work per- 

 formed by it in coal-mines, has naturally also received much 

 attention. A reduction in the volume of flame produced by 

 gunpowder when used as a blasting agent has been effected 

 by modifications in its compoition, but the best result at- 

 tained until recently in this direction had not materially re- 

 duced the danger of using powder in the ordinary manner. Some 

 promising results are, however, said to have been quite lately 

 attained in Germany with a special powder produced by the 

 original maker of the now celebrated cocoa powder, the pub- 

 lication of which is looked for with much interest. 



Special forms of gun-cotton were prepared for use in coal in 

 the early days of the improvements made in its preparation ; 

 but the large proportion of the inflammable and poisonous gas, 

 carbonic oxide, which its explosion furnishes, prohibits its em- 

 ployment in this direction, even in the form of preparations 

 coming under the head of nitrated gun-colton, which yields com- 

 paratively small proportions of carbonic oxide. 



Nitro-glycerine contains actually more oxygen than required 

 for the complete burning of its constituents, carbon and hydro- 

 gen, and hence its detonation in the open air is attended only by 

 the appearance of a lightning-like flash of light. When diluted 

 with an inert non-combustible material, as in dynamite, its de- 

 tonation raises to a high red heat the particles of mineral matter 

 with which it is mi.sed, many of which are, therefore, projected 

 in a glowing state, like a shower of sparks, if the dynamite be 

 fired in a strong shot-hole. Even with Nobel's blasting gelatine, 

 the latest and most powerful explosive, a blown-out shot may be 

 attended by the projection of some glowing particles, either of 

 the tamping or detached from the blast-hole. 



The Commissioners have satisfied themselves by many ex- 

 periments that an explosive mixture of gas and air may be 

 exploded by the projection into it of such sparks, and that they 

 may even occasionally produce ignition, when projected into air 

 containing only a small proportion of fire-damp, but in which 

 coal-dust is thickly suspended. 



The outline which I have given you of the dangers attending 

 the use of explosives in coal mines, and of the apparently unsur- 

 mountable difficulties attending any attempts to approach 

 immunity from the two great elements of danger naturally exist- 

 ing in a very large proportion of coal mines, namely, fire-damp 

 and dust, will probably lead you to the conclusion that there is 

 but one effectual method of dealing with the serious question of 

 accidents due to explosions in coal mines, namely, that of en- 

 forcing the exclusion of the use of explosives in coal mines. 



In the House of Commons debate of June, 1878, Mr. 

 MacDonald, while acknowledging that the provisions of the Coal 

 Mines Regulation Act of 1S72, for prevention of accidents 

 through the use of gunpowder in fiery mines, had been pro- 

 ductive of great good, insisted that these regulations were 

 insufficient to guard against fire-damp explosions, and referred, 

 in illustration, to the fact that the firing of the shot itself might 

 liberate a large quantity of gas, which no previous inspection 

 would discover. He urged in the strongest terms that, until 

 blasting in any fiery mine were absolutely prohibited, there 

 must be a continual recurrence of terrible disasters ; and, in the 

 debate whicli followed, there was a general consensus of opinion 

 among the speakers most competent, from personal experience, 



