May 4. 1882] 



NA TURE 



in it, warranted the concision that coal-dust also might, under 

 certain conditions, originate an > l11 as carry ii on 



to some considerable extent. The results obtained by the corre- 

 sponding experiments of the Chesterfield Committee appear to 

 support 'this vieiv, and Mr. Galloway has also, by his later 

 experimental results, been led to the same conclusion, and con- 

 siders that the results of hi- examination into the effects pro- 

 duced by some of the most serious of recent coal-mine explosions 

 (at Penygraig, Risca, and Seaham) demonstrate that those 

 e\] 1 1 1 ms were chiefly, if not entirely attributable to coal-dust. 



Notwithstanding the considerable light tl at was thrown on 

 this subject so far back as 1845 by Faraday and Lyell, and 

 the accumulation of experimental and other observations re- 

 the action and effect of coal-dust in colliery explo- 

 sions, the e have not until quite recently received the attention 

 which they merit at the hands of mine owners, and many of 

 those in authority connected with coal-mines. Evidence collected 

 by the Royal Commission on Accidents in Mines, from mine 

 inspectors and leading mining eng neers (and published with the 

 preliminary Report of the Commission), show the preponderance 

 of opinion to be against the view that explosions could originate, 

 or be to any great extent propagated, by coal-dust, in the 

 absence of fire-damp, though the belief is entertained by many 

 that the coal-dust may be credited with an extension or aggrava- 

 tion of explosions caused by fire-damp. On the other hand, 

 there is a great tendency exhibited always to ascribe explosions 

 which do not admit of satisfactory explanation, by an accidental 

 failure of ventilation or other evident causes, to a sudden disen- 

 gagement, or outburst, of fire-damp, such as is of no uncommon 

 :• in fiery mines, and is sometimes very serii us in its 

 magnitude and duration. That such outbursts, following upon 

 falls of roof and the firing of blast holes, have been the cause of 

 many disastrous explosions, there can be no doubt, but, in some 

 instances, the conclusion that an explosion had been due to this 

 cause, is based upon assumptions and upon very doubtful 

 evidence. Under any circumstances, it is extremely difficult to 

 realise how sufficient gas to produce an explosive atmosphere, 

 can be conveyed, even by the most powerful currents, from the 

 seat of such a sudden outburst to far distant portions of the 

 mine, to which the burning effects of an explosion have been 

 found to extend, within the period believed to have elapsed 

 between the first outburst of gas and the ignition of an explosive 

 atmosphere formed in its vicinity. On the other hand, the 

 evidence of severe burning, after an explosion, such as could not 

 be produced by the rapid explosion of a gas-mixture alone, and 

 thedeposition of partially burned coal-dust in distinct parts of a 

 mine, distant from each other and from the point to which the 

 origin of the explosion has been traced, seem to leave no doubt 

 that coal-dust has played an important part in many of the 

 explosions which have of late been subjected to rigorous 

 investigation. 



The strong impression entertained by many, during the inquiry 

 into the great explosion at Seaham Collieries, in September, 

 1880, that coal-dust might have had much to do with the acci- 

 dent, and that the explosion was possibly even entirely due to 

 the ignition of coal-dust by a blown-cut shot, in the absence of 

 any fire-damp, led to Mr. Abel's being requested by the Home 

 Secretary to make experiments with samples of dust collected in 

 the mine, and to an extension of these experiments to dust col- 

 lected from collieries in different 1 arts of the kingdom where 

 explo.-ions had occurred. 



The results of experiments conducted with great care and on 

 an extensive scale at a colliery in Lancashire, where a constant 

 supply of fire-damp was brought to the pit's mouth from a so- 

 called blower, confirmed ihe fact demonstrated by M. Vital and 

 Mr. Galloway, that the propagation of fire by coal-dust, when 

 thickly suspended in air, is established or greatly promoted by 

 the existence, in the air, of a proportion of firedamp, which 

 may be so small as to escape detection by the means ordiaarily 

 employed (such for example as exists in the return-air of a well 

 ventilated mine). 



It was also established that a mixture of fire-damp and air 

 approaching in proportion those required to be explosive, would 

 be ignited by a flame if only a small proportion of dust were 

 floating in it. Further, it was demonstrated that, although 

 those dusts which were richest in inflammable matter, and most 

 finely divided, were the most prone to inflame and to carry on 

 flame, in the presence of small quantities of fire-damp, some 

 "usts which contain coal only in comparatively small proportions 



ere as sensitive as others much richer in inflammable matter, 



and that even certain perfectly non-combustible dusts possessed 

 the property of establishing the ignition of air- and gas-mixtures 

 which, in the absence of dust, were not ignited by a naked 

 flame. This action of non-combustible dusts appeared to be due 

 to physical peculiarities of the finely-divided matter, and to be 

 perhaps analogous to the contact-action well known to be pos- 

 sessed by platinum and son e other bodies, whereby these bring 

 about the rapid oxidation of gases which, in their absence, may 

 exist intact in admixture with oxygen or air. 



Many experiments were tried with sensitive coal-dust from 

 Seaham and other collieries, for the purpose of ascertaining 

 whether results could be obtained supporting the view that coal- 

 dust, in the complete absence of fire-damp, is susceptible of 

 originating explosions and of carrying them on indefinitely, as 

 suggested by some observers, but, although decided evidence 

 was obtained that coal-dust, when thickly suspended in air, will 

 be inflamed in the immediate vicinity of a large body of flame 

 projected into it, ana will sometimes cany on the flame to some 

 small extent, no experimental results furnished by these experi- 

 ments warranted the conclusion that a coal-mine explosion could 

 be originated and carried on to any considerable distance in the 

 compute absence of fire-damp. Some experiments made in a large 

 military gallery at Chatham showed that the flame of a blow n-out 

 shot of 14 lb. or 2 lb. of powder might extend to a maximum 

 distance of 20 feet, while in a very narrow gallery, similar to a 

 drift-way in a mine, the flame from corresponding charges 

 extended to a maximum distance of 35 feet. These distances 

 are considerably inferior to those which flame from blou n-out 

 shots has been known to extend, with destructive results, in coal- 

 mines, and there appears no doubt that, in the latter cases, of 

 which the lecturer gave examples, the flame was enlarged and 

 prolonged by the dust raised by the concussion of the explosion. 

 But, in these examples (with charges of I lb. of powder), the 

 flame did not extend much beyond a distance of 100 feet, and 

 therefore the power of the dust to carry an explosion or flame in 

 these cases was limited. It was found, in experiments with the 

 large Chatham gallery, in which the flame from a blown-out shot 

 reached, in the absence of dust, to a maximum distance of 20 

 feet, that, when the atmosphere was thickly laden with a highly 

 inflammable coal-dust, from Seaham Collieries, the flame was 

 carried on to nearly double, and in one case a little more than 

 double, the distance. 



Although it may be very doubtful whether coal-dust, in the 

 compute absence of fire-damp, can be credited with the production 

 of extensive explosions, as has been recently maintained by some, 

 there can be no question that, in the presence of only very small 

 quantities of fire-damp, it may establish and propagate violent 

 explosions ; and that, in the case of a fire-damp explosion, the 

 dust not only, in most instances, greatly aggravates the burning 

 action and increases the amount of after-damp, but that it may 

 also, by being raised and swept along by the blast of an explo- 

 sion, carry the fire into workings where no fire-damp exi-ts, and 

 thus add considerably to the magnitude of the disaster. The 

 supposition that extensive coal-mine explosions may be produced 

 by coal-dust alone, in the complete absence of gas, necessitates 

 the fulfilment of conditions which cannot but be at any rate very 

 exceptional, but its acceptance is unnecessary to add to the for- 

 midable character of coal-dust as a source of danger and an 

 agent of destruction in mines. The possibility of dealing with 

 the dangerous dust in mines should therefore be as much an 

 object of earnest work as has been the improvement of venti- 

 lating arrangements in mines. 



The actual removal of dust-accumulations being in most 

 instances impracticable, the laying of the dust by an efficient 

 system of watering the mine ways, is a matter deserving serious 

 atttntion. Although in some instances such a measure is not 

 readily applicable, without injury to the workings, it has been 

 already proved in some districts to be unobjectionable and sus- 

 ceptible of very beneficial application. The employment of 

 deliquescent substances (calcium chloride, sea-salt, &c), in con- 

 junction with watering, has also been advocated and tried to 

 some extent with success. 



The elaboration of really safe and sufficient methods of getting 

 coal where blasting by powder is now resorted to, and of re- 

 moving the harder rock in the working of drifts, &c, where 

 fire-damp may exist, must most importantly contribute towards 

 the diminution of danger arising from the accumulation of dust 

 in mines, both by avoiding the projection of flame into the air, 

 and by avoiding powerful concussions, whereby dust is raised ; 

 and the lecturer referred in conclusion to the various plans, in 



