NA rURE 



[Jan. 6, \\ 



England her letters were restored to her, and in the 

 present volume she has arranged them in chronological 

 order, with extracts from her journal. The book contains 

 a mass of petty details in which few readers will find 

 much to interest them ; but there are also some very good 

 sketches of the scenery of Natal and of the rough, free- 

 and-easy life of the colonists. Mrs. Feilden was much 

 impressed by the fertility of the soil, and by the beauty of 

 the vegetation with which she was surrounded. " As for 

 fruits, vegetables, and flowers," she wrote, " you have only 

 to put the seeds and young plants in the ground and they 

 grow. There is no end of season in Natal." She remarked 

 that there were not many native fruits, but that all that 

 were imported seemed to suit the soil and climate. The 

 native flowers she considered " very exquisite." They 

 "grew in great variety and luxuriance, with the waxy look 

 of hot-house plants.'' As for birds and insects, the air 

 teemed with them. Of the Caffres Mrs. Feilden formed a 

 very poor opinion. '' The Caffre is indolent ; he lives only 

 like the beast, to eat and sleep, and pass through life with 

 ease ; but to do this he must have his land tilled, and to 

 purchase wives to till his land he must have cows to pay 

 for them. He sells his daughters to be drudges to other 

 Caffres, while the boys and young men go out to work for 

 the white man, till they can in turn buy cows and wives." 

 Even Caffres, however, have one good c|uality : " they 

 heartily share anything they have with each other, and eat 

 out of the same pot without the least feehng of who shall 

 have most." To Mrs. Feilden they seemed to be rather 

 like Jews, and she asks whether they may not be 

 descendants of Ishmael or an oftshoot from the lost 

 tribes — from whicli it may be inferred that in the list of 

 subjects she has tried to study ethnology has not yet been 

 included. 



LETTERS TO THE EDITOR 



[The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake to 

 return, or to correspond ivith the writers of, rejected manu- 

 scripts. No notice is taken of anonymous communications. 



[ The Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 that it is impossible othenvise to insure the appearance even 

 of communications containing interesting and novel facts. ] 



The Coal-Dust Theory 



Under the title of " A New Mining Danger," the Yorkshire 

 Post of the i6th ult. published its final report on the proceed- 

 ings at the inquest on the bodies of twenty-two men and boys 

 who perished in an explosion at Altofts Colliery, Normanton, 

 on the 2nd of October last. 



The inquest was commenced immediately after the explosion, 

 but was adjourned until the workings could be sufficiently re- 

 opened to admit of a careful examination being made into all 

 the circumstances. It was resumed and concluded on the 13th, 

 14th, and 15th of December. The witne-ses, including Mr. F. N. 

 Warden, Her Majesty's Inspector of Mines for the district, were 

 unanimously of opinion that the explosion was originated by the 

 firing of a shot in the stone or rock constituting the side of one 

 of the main thoroughfares of the colliery, which was also a main 

 intake airway ; and they w ere of opinion that it had expended 

 part of its energy in raising and igniting a cloud of coal-dust, 

 which formed the nucleus whence the explosion was propagated. 



The coroner in summing up agreed with this conclusion, 

 and the jury returned the following verdict : — 



" That the whole of the workmen killed, except Deakin and 

 Lomax, met their deaths from an explosion of coal-dust, which 

 originated in the west chain road, which explosion was cau-ed 

 by the firing of an unskilfully drilled shot by one of the men 

 engaged in widening the road ; and that Deakin and Lomax 

 were suffocated by the stoppage of ventilation consequent on the 

 explosion." 



The coal-dust theory, which is discussed at some length 

 in the Final Report of the Royal Commissioners on Accidents 



in Mines, postulates that coal-dust may not only serve to 

 originate an explosion, under certain given conditions, but may 

 continue to carry it on as far as the same condition-; extend. 

 The essentia! conditions appear to be : that the coal-dust be per- 

 fectly dry, in a ve y fine state of division, and fairly abundant in 

 quantity ; that the initial cause be a large flame expanding with 

 sufficient foice to propel the air rapidly in front of it, so as to 

 raise a cloud of coal-dust ; and, lastly, that the explosion take 

 place in a confined space, such as the workings of a mine. 



Frf^m the first this theory was intended to account for great 

 explosions in mines, or accomplished facts, which seemed to be 

 otherwise inexplicable. It has nothing to do with mines in 

 which explosions have not taken place, except to point out a 

 possible source of danger ; and arguments opposed to it 

 which are based upon the fact that all kinds of coal-dust are 

 not equally inflammable are therefore obviously inapplicable. 

 It wa-i adopted by the Prussian Commissioners as being 

 applicable to certain inflammable dusts in a minute state 

 of subdivision, but not to others of a somewhat different 

 chemical composition. In discussing the Camphausen explosion 

 in Nature (vol. xxxi. p. 13), I pointed out that the con- 

 clusions arrived at from a consideration of the experimental 

 results obtained with Camphausen dust by the Prussian Com- 

 missioners, fell far short of the actual occurrence in the colliery, 

 and that the same relation would probably obtain in the case of 

 all the other dusts experimented with, provided all were made 

 equally fine. 



MM. Mallard and Le Chatelier, whose conclusions were 

 accepted by the French Commission, of which they were mem- 

 bers, rejected the coal-dust theory, and endeavoured to reason 

 away all apparently confirmatory arguments drawn from the 

 consideration of actual explosions in mines. 



In this country it has been accepted by some of the 

 Inspectors of Mines, and more particularly by Messrs. W. N. 

 and J. B. Atkinson, who uphold it vigorously in their treatise 

 on "Explosions in Mines," which was recently reviewed in 

 Nature (Nov. 4, 1S86, p. i) by Prof Thorpe. It appears also 

 to have found favour with a number of mining-engineers and 

 colliery managers, both here and abroad. There seems, how- 

 ever, to be some doubt as to how far it was accepted by the 

 Royal Commissioners on Accidents in Mines, and I shall 

 dierefore quote their own words on the subject : — 



" In emphasising this claim (Proc. Roy. Soc, vol. x.xxvii. 

 p. 43), Mr. Galloway does not appear to have realised the fact 

 that, if dust were the principal agent in coal-mine explosions, 

 every blown-out shot occurring in a z'cry dusty and dry mine 

 .should actually be attended by a more or less disastrous ex- 

 plosion or conflagration, and that, looking therefore to the 

 enormous amount of powder expended in shot-firing in this and 

 other countries, and to the not inconsiderable proportion which 

 blown-out shots must constitute, in many localities, of the total 

 number of shots fired, disastrous coal-mine explosions should be 

 of more than daily occurrence, if his view were correct." 



I submit that the conclusion here stated is not deducible from 

 the premiss ; and in support of this position I adduce the fact 

 that coal-dust is admitted to have been the principal agent in 

 two of the most disastrous explosions of the present year, 

 namely, those of Mardy and Altofts collieries, in both of 

 which shots wee fired. Altofts Colliery alone is sufficient to 

 prove the case against the Commissioners, for it has been in 

 operation for twenty-one years, and shot-firing has been carried 

 on in it during the whole of that period. If, then, blown-out shots 

 constitute a " not inconsiderable proportion " of the whole, there 

 is a probability amounting to a certainty that such shots must 

 have been fired in Altofts Colliery many times without the results 

 here postulated having been attained until now. The argument 

 as made use of against my own views appears therefore not to 

 be in accordance with ascertained facts. 



It may be safely maintained, therefore, that every blown-out 

 shot doci not fulfil the whole of the conditions nece-sary for 

 creating an cplosion. For instance, the dust may not be 

 present in sufficient abundance within reach of the flame ; it 

 may not be fine enough to ignite at the point where the shot 

 explodes ; it may contain too much foreign matter, or be covered 

 with coarse rubbish, or be locally damp ; the .shot may be too 

 high, or too low, or p jinted in ai unfavourable direction; the 

 direction and velocity of the passing air-current may exercise 

 some influence on the result ; the creation of a nucleus of 

 explosion may in certain cases be facilitated by the previous 

 formation of a cloud of coal-dust to windward, raised ly another 



