224 



NATURE 



[April 13, 191 1 



recrudesrence havinf! set in later, it became apparent to 

 those who wfTf! walchinjj the course of events that complete 

 immunity could not be attained until measures were adopted 

 Inr <i. :ilinfj with the coal dust in the haulaf^e roads, as well 

 .1 1; ilx! points at which blastinf^ shots were about to be 

 lirttl. It was equally apparent that no far-reaching legis- 

 lative action such as this could be taken unless the mining 

 community, which had hilherto regarded the dangers of 

 coal dust as more or less hypothetical, could be convinced 

 of their reality, by ocular demonstration on a large and 

 imposing scale. Accordingly, when called upon to give 

 evidence before the Royal Commission on Mines some 

 years ago, the present writer and others recommended the 

 construction at Government expense, at an estimated cost 

 of 10,000/., of a large apparatus to be used for this purpose. 

 It is, perhaps, needless to remark that the Treasury 

 declined to find the money, just as they had, some twenty- 

 nine years ago, declined to find 5000/. for the construction 

 of a similar gallery, 500 feet long by 6 feet in diameter, 

 intended to be used for the same educative purpose, when 

 asked to do so by the Royal Commission on Accidents in 

 Mines, for one of' the menibers of which (Sir W. Thomas 

 Lewis) the present writer had obtained tenders. 



The suicidal blindness of this kind of policy from a 

 national point of view must surely be becoming apparent. It 

 was at this juncture that the Mining Association of Great 

 Britain stepped in and erected the experimental gallery at 

 Altofts Colliery, which has been already described in a 

 previous review (Nature, February 0, vol. Ix.xxv., p. 487). 



When it was recognised in France that the explosion at 

 Courri^res Collieries, which claimed more than 1100 

 victims in 1906, was due to coal dust alone, the opposition 

 which the Commission du Grisou had, up to that time, main- 

 tained against the coal-dust theory was effectually crushed, 

 and it became necessary for those resf>onsible for the safety 

 of French mines either to accept the data regarding the 

 behaviour oi, and means of dealing with, coal dust already 

 accumulated in other countries, or to accumulate quasi- 

 original data of their own. The opportunity of adopting 

 the latter alternative presented itself when the Comitd 

 Central des Houill^rcs de France aprreed to find a capital 

 sum of i4,oooI. wherewith to provide experimental appli- 

 ances, and an annual income of 3000Z. a year for current 

 expenses as long as the experiments are continued. 



The appliances which have been set up at Li^vin Collieries 

 in France are similar to, and intended to serve the same 

 purposes as, those at Altofts and other experimental 

 stations. 



The experiments are being conducted by M. TafTanel, a 

 member of the Corps des Mines, who has issued consecu- 

 tively a number of very clear and able reports, describing 

 the appliances, the methods of using them, and the results 

 obtained with them. 



In attempting, in his first report, to justify the attitude 

 of antagonism to the coal-dust theory which his colleagues 

 had just abandoned, he essays to throw a dart at the 

 work of the present writer, but the weapon, having 

 the form of a boomerang, naturally descends upon the 

 unhappy heads of those he is trying to protect. 

 It could not well be otherwise, for his subsequent 

 voluminous descriptions of the mode of occurrence of a 

 coal-dust explosion, the functions of the condensed and 

 expanded waves and the position of the flame in the 

 former, the influence of the weight of dust in a given 

 volume of air, its fineness, the proportion of volatile matter 

 contained in it, and the presence of more or less inert 

 matter and moisture, had all been anticipated in the work 

 in question ; so that his own contributions to the subject, 

 when divested of a vast amount of prolixity and a great 

 arrav of numerical data, much of which is of doubtful, 

 and most of only hypothetical value, largely partake of the 

 nature of plagiarism. 



Numerical data obtained by means of experiments of this 

 kind are of no practical value except in so far as they can 

 assist us in devising' means for putting an end to great 

 explosions. Thus, as it is known that the flame of an 

 explosion in a mine can ascend to the top of a damp or 

 wet shafi 900 or 1000 feet deep, it is not of the least 

 importance to know whether an explosion in an experi- 

 mental gallery can or cannot leap across a dustless zone a 

 few hundred feet in width, and raise and ig^nite coal dust 

 lying at its farther side. It is equally unimportant to 



NO. 2163, VOL. 86] 



know with what velocity the flame traveK i 



particular pressure is exerted by, an explosion ui duM f 



greater or less fineness, or containing more or !^<i vo!-- :<• 



matter, nince we are absolutely powerless to 



one of these conditions in a dusty mine, and 



explosion, once begun in it, will spread as fu. us im:' , 



coal dust to maintain it. 



In further attempting to cover the retreat of his cf, ti- 

 rades, M. TafTanel pleads that they had no previa 15 

 experience of coal-dust explosions in France before the <.:.e 

 at Courri^res Collieries. But the present writer has a 

 lively recollection of reading the accounts of two great 

 explosions at th? Jabin pits in France, which occurred one 

 after the other within a short period of time, some thirty 

 or more years ago, and of making a mental note at the 

 time that, judging by the phenomena as dcscril)ed, they 

 were both due to coal dust and not to firedamp, as was 

 then announced. Again, surely M. TafTanel does not now 

 seriously contend that the four great explosions, Chatdus^ 

 1887, Verpilleux, 1889, Pefissier, 1890, and Manufao* 

 ture, 189 1, were attributable to any other agent than coal 

 dust. 



We frankly agree with M. TafTanel that his countrymea 

 are, as a rule, in the van of progress ; that although they 

 did not originate the method of measuring the proportion of 

 firedamp in the air by means of the firedamp cap {for this 

 see Proc. Roy. Soc., vol. xxiv., pp. 361 to 367), they have 

 produced an excellent lamp for the purpose ; and that their 

 appliances and regulations for dealing with firedamp, and 

 for blasting, are amongst the most perfect in existence, and 

 we heartily congratulate him and them upon the results of 

 these measures. But qui s'excuse s'accuse : and the mere 

 fact that they have been able to perfect their methods of 

 dealing with firedamp makes it all the more regrettable 

 that they so resolutely refused to believe in the dantjers of 

 coal dust, since it is practically certain that had they lent 

 their powerful aid to the solution of that question from the 

 beginning, it would have been settled long ago, and at least 

 two Royal Commissions which examined the subject succes- 

 sively in this country would ha%-e been saved the ignominy 

 of making halting and half-hearted suggestions for 

 grappling wiTh it. 



The first series of M. Taffanel's experiments was made 

 with an auxiliary apparatus consisting of two pieces of sheet- 

 iron pipe, each 25 feet long by 2 feet in diameter, placed side 

 by side and connected to each other at each end by short 

 pipes of the same diameter. The air was made to circulate 

 through this system by means of a fan working at the 

 middle point of one of the longer pipes with sufficient 

 rapidity to keep fine dust suspended in it, and shots were 

 fired from a cannon into the dust-laden air from one end 

 or the other of the second long pipe. By this means it was 

 ascertained that dust containing 11-3 per cent, of volatile 

 matter (ash and moisture deducted) could not be ignited by 

 the explosion of a half cartridge of gelatine dynamite fired 

 electrically from the cannon without tamping, but that dust 

 containing 154 per cent, and up to 53-2 per cent, could be 

 invariably ignited when the air contained a minimum 

 weight of 138 grammes per cubic metre of that with 15-4 

 per cent, and 40 grammes per cubic metre of that with 

 i;3-2 per cent., and similarly an intermediate weight for an 

 intermediate proportion of volatile matter. 



The second series of experiments was made with the 

 same apparatus (the shots being fired in the direction of 

 the air current), one set to ascertain the effect of varying 

 the weight of the explosive, the other to determine the 

 effect of mixing the coal dust with slate dust. The coal dust 

 employed 5'as prepared with Li^vin coal containing 29 to 

 30 per cent, of volatile matter and 3 to 5 per cent, of 

 ash, and of such a degree of fineness that only s per cent. 

 of it was unable to pass through the sieve with 5625 meshes 

 per square centimetre. 



By these experiments it was ascertained, first, that a 

 certain minimum weight of explosive was sufficient to 

 produce ignition, and that in'-'easing that weight made 

 little or no dilTerence in the length of the resulting coal-dust 

 flame ; and, secondly, that the addition of slate dust to the 

 coal dust reduced the velocity of propagation of the flame, 

 although inflammable clouds were obtained with as much 

 as 62 per cent, of slate dust, and it seemed doubtful whether 

 under certain conditions propagation would not take place 

 with as much as 78 per cent. 



