482 



NATURE 



[March 23, 1893 



Vital, one of the Ingdnieurs des Mines, with the object of 

 ascertaining the likelihood or otherwise of this hypothesis, 

 but no definite conclusions were arrived at. 



In December, 1 875, the present writer examined into all 

 the circumstances attending a colliery explosion in South 

 Wales,andgaveaminutedescriptionofitbeforeacoroner's 

 jury. He insisted that coal-dust had been the principal 

 agent in that explosion, and that firedamp had only played 

 a subordinate part. At the same time he referred to the 

 results of experiments he had made which showed con- 

 clusively that when fine dry coal-dust is added to a 

 mixture of air and firedamp, in which the firedamp is 

 present in so small a proportion as to escape detection 

 by the means employed for this purpose in mines, the 

 mixture is inflammable at ordinary pressure and tem- 

 perature, and when ignited burns like a jet of inflammable 

 gas. In March, 1876, he read a paper before the Royal 

 Society, in which he described these experiments, as 

 well as the apparatus with which they had been carried 

 out. In this paper, also, he claimed that when an explo- 

 sion is once begun in a dry and dusty mine it becomes 

 self-propagating, and, provided the continuity of the 

 deposit of coal-dust is unbroken, it extends to the utmost 

 limits of the workings. This became known afterwards 

 as the '' Coal-dust Theory of Great Colliery Explosions." 

 In May, 1876, Mr. Hall, one of the Inspectors of 

 Mines, read his first paper on the subject before a meet- 

 ing of the North of England Institute of Mining and 

 Mechanical Engineers held in London. 



During the year 1878 the present writer published a 

 series of papers on " Coal-dust Explosions" in " Iron " ; 

 and while they were appearing Messrs. Marrecco and 

 Morrison read their first paper on the subject. 



Numerous societies of mining men, and individuals 

 more or less connected with mining, now began to take 

 an interest in the subject, and to make experiments with 

 coal-dust. About this time, also, Commissions were 

 appointed by the Governments of England (Royal Com- 

 mission on Accidents in Mines 1879), France (Commis- 

 sion du Grisou), Prussia and Austria, to inquire into the 

 causes of mining accidents, and amongst other things to 

 investigate the probable influence of coal-dust in colliery 

 explosions. 



This sudden activity was no doubt quickened by the 

 events of the ten years ending with 1880, during which 

 the loss of life from explosions was twice as great as it 

 had been during any previous decade. Taking into 

 account only those explosions in which ten lives and 

 upwards were lost, we find that there were thirty-five 

 explosions, involving the lives of 2014 persons, of which 

 141 1 were attributable to the second half of the decade. 



In 1880 Prof, (now Sir Frederick) Abel, one of the 

 English Commissioners, was instructed by the Home 

 Secretary to investigate and make a special report upon the 

 Seaham colliery explosion (September 8, 1880). During 

 the course of these investigations Abel repeated our 

 experiments of 1875-76 with a similar apparatus with 

 practically the same results as far as coal-dust is 

 concerned ; but he claimed in addition to have dis- 

 covered that any very finely divided incombustible dust 

 would render a mixture of air with 3 or 4 per cent, of fire- 

 damp inflammable. His apparatus was not, however, 

 provided with any special means of mixing the gas and 

 NO. 122 I, VOL. 47] 



air such as had been used in our own apparatus, of which 

 it was otherwise a copy. 



The German Commissioners erected and made ex- 

 periments with an apparatus similar to one that we had 

 described to the Royal Society in 1881, but on a some- 

 what larger scale, and they obtained similar results. 

 Unfortunately, however, they passed away from the 

 main question, viz. whether an explosion that has taken 

 place in a dry and dusty mine under the circumstances 

 that would have been formerly described as mysterious, 

 can be attributed to the influence of the coal-dust in the 

 supposed absence of firedamp ? 



The French Commissioners arrived at conclusions ad- 

 verse to the coal-dust theory. They made no special 

 experiments with coal-dust on an important scale and they 

 did not, so far as can be gathered from their reports, 

 examine the workings of any mine immediately after an 

 explosion. 



The Austrian Commissioners arrived at the conclu- 

 sion which we had previously stated in this country, 

 namely, that the relative fineness of a dust has far more 

 to do with its relative inflammability than its chemical 

 composition. 



The English Commissioners expressed an oracular 

 opinion. They denied on the ona hand that coal-dust 

 could be the principal agent in great colliery explosions, 

 for, "If that were the case," said they, "an explosion 

 would happen every day, nay every hour." But, on the 

 other hand, they endeavoured to point out that coal-dust 

 may be an element of the gravest danger under certain 

 circumstances which they proceeded to define in a very 

 precise manner. The Act of 1887 embodies their 

 recommendations regarding safety lamps, explosives, and 

 coal-dust. 



From the end of 1875 onwards attention had been- 

 more and more directed to the coal-dust question. It 

 had been observed that a great explosion never by any 

 chance took place in a damp or wet mine, that when 

 such an explosion took place in a dry and dusty mine, its 

 progress was always arrested by dampness or wetness or 

 by the absence of coal-dust, that it always passed through 

 the dry intake airways, which contain pure air, and 

 comparatively clean coal-dust, that it frequently avoided 

 the return airways, which contain all the firedamp pro- 

 duced in the workings, but impure coal-dust or only 

 stone-dust, and, lastly, that it spread into all the districts 

 of the workings ventilated by separate and distinct intake 

 and return airways, quite irrespective of the force or 

 direction of the ventilating currents, and dependent only 

 upon the one simple but indispensable condition that the 

 train of dry coal-dust continued unbroken, or was inter- 

 rupted only for short distances here and there. These 

 facts were proved to demonstration by the researches of 

 anumber of independent observers in the mines themselves, 

 immediately after the occurrence of explosions. In vain 

 have the opponents of the coal-dust theory, who were at 

 one time very numerous, urged that the intake airways 

 might have contained firedamp, that the coal-dust cloud 

 raised and ignited by a local disturbance, such as the 

 firing of a blasting shot, probably acted as a connecting 

 link which carried the flame from one accumulation of 

 firedamp to an ither, that if coal-dust was as dangerous 

 as it was represented to be, an explosion would take place 



