490 



NATURE 



[February 9, 191 1 



N umber 



ofexpe- 1-2 2-3 3-4 4-5 Page 



riment 

 102 113-5 85-0 ... 1180 554-5 ... 191 



104 I3S-5 3205 ... 1600 450-5 ... 196 



105 632-0 52-9 ... 1250 143-5 ••• 200 

 Considered as a whole, these results are so discordant 



that it is impossible to draw any other conclusion from 

 them than that either the instruments are at fault or that 

 there is some disturbing element at work, due, most 

 probably to variableness in the quantity of dust suspended 

 in the air in different sections of the gallery when the 

 flame of an explosion is traversing it. 



Owing to the very nature of the experiment, it is 

 obviously impossible to provide that each section shall 

 always contain the same quantity of dust, mixed with the 

 same degree of uniformity in the air which occupies it, 

 at the instant an explosion is passing through it. It is 

 equally obvious that, unless that condition can always be 

 rigidly complied with, the results cannot be concordant as 

 between one section and another, although the sum of the 

 results may seem to be fairly uniform when one explosion 

 is compared with another. But the same absence of 

 uniformity must necessarily obtain in the workings of a 

 mine when an explosion is passing through it, and, there- 

 fore, if the aim of the committee is to reproduce that 

 phenomenon as nearly as possible in their artificial gallery, 

 the observed discordances show that they have already 

 succeeded in doing so. 



The haulage roads, along which the coal is conveyed 

 from the working places to the shaft, contain larger 

 quantities of very fine coal dust than any other parts of 

 a mine, and ever since the time when the coal-dust theory 

 of great explosions was first propounded,^ they have been 

 recognised as the routes along which explosions, com- 

 menced at any point in a mine, travel to every other part 

 of the workings, however remote. This was well 

 exemplified in the plan which accompanied the description 

 of Penygraig Colliery explosion ^ (1880), previously re- 

 ferred to. It has also been recognised, of course, that 

 if coal dust could be prevented from accumulating in the 

 roadways, or be rendered innocuous by water or other 

 means, the range and disastrous effects of explosions 

 would be greatly limited. To prevent accumulation in the 

 first place by the employment of mine-waggons with dust- 

 tight bodies, ^lled only to the brim and provided with 

 covers, is obviously the best possible expedient that could 

 be adopted, and would be infinitely preferable to the pre- 

 sent careless system of carrying the coal in all sorts of 

 leaky or over-loaded waggons, from which it dribbles or 

 falls upon the roads, and is then ground or trodden into 

 the very dust which constitutes the danger. 



Under existing conditions, as regards the mode of con- 

 struction of mine-waggons, the production of coal dust is 

 inevitable ; and although there is no legislative enactment 

 in this country compelling the mine-owners to do so, 

 many of them already water the dust in their haulage 

 roads once or twice a day in order to render it innocuous. 

 But in many other mines water cannot be used for this 

 purpose, as it causes the ground above or below the seam 

 to swell or fall to pieces, and consequently the dust is 

 allowed to remain dry. It has been proposed to give the 

 owners of the latter class of mines the alternative of 

 rendering the dust innocuous by covering it from time to 

 time with inert dust, or with a hygroscopic or other salt. 

 The committee have, accordingly, directed their attention 

 to the question of using inert dust for this purpose, and 

 made careful experiments, which are described in chapters 

 vi. and vii., to ascertain, first, the effect that dust of this 

 nature has in arresting the progress of an explosion, and, 

 secondly, the cost of applying it practically in Altofts 

 Colliery. 



The inert dust for both purposes has been prepared bv 

 grinding _ the roof-stone of one of the seams of Altofts 

 Colliery in a roller-mill at a cost of 2s. per ton. 



In the five following experiments a standard length of 

 275_ feet of the gallery was strewn with coal dust, the 

 Igniter was fired at the inner end of this zone, and the 

 space at its outer end, 150 feet in length, was treated as 

 follows : — 



^ Proc. Roy. Soc, vol. xxiv., p. 354 (1876). 

 2 Loc. cit. 



NO. 2154, VOL. 85] 



Number 

 of expe- 

 riment 



55 • 



57 • 



5« . 



62 . 



116 . 



Left dustleAS or strewn with 

 stone dust or coal dust 



Pressures recorded 

 by ihe manometers 



Du>tless 



150 



Stone dust Coal dust 

 ft. It. 



150 

 100 



50 

 50 

 50 



H 



lb. 

 40 

 40 

 31 



395 

 337 



A 

 lb. 

 100 



9 



17-5 

 84 



9-18 



In experiment 55 the flame passed just beyond the out' 1 

 end of the dustless zone; in 57 it penetrated 55 feet ini.; 

 the stone-dust zone ; in 58 it penetrated 54 feet into th^- 

 stone-dust zone ; in 62 it passed through the dustless and 

 coal-dust zones, and shot out 100 feet beyond the latter : 

 in 116 it penetrated 22 feet into the stone-dust zone. 



These experiments show that a zone of stone dust 

 more efficient in arresting an explosion than a dustli 

 zone, and thus help to answer, but do not complet- . 

 solve, one of the questions still being considered by tl 

 Royal Commission on Mines, as to whether it is desira! 

 to compel the owners of mines in which water cannot 1^ 

 employed for the purpose of laying the dust to surround 

 certain lengths of the main roadways with brickwork or 

 concrete, and keep these lengths continually wet. 



In chapter vii. it is shown that it costs 1-85^. per yard 

 in Altofts Colliery and 2d. per yard in New Moss Collier} , 

 which is under the same management, to " dress " th- 

 roadways with stone dust. The experience obtained in 

 Altofts Colliery, which is practically free from coal du- 

 in consequence of the fact that many of the mine-waggoi 

 are dust-tight, the remainder nearly so, that none are 

 filled above the level of the brim, and that the traffic is 

 very slow, is inapplicable to the case of most other mines 

 in which all, or nearly all, these conditions are exactly 

 the reverse, so that no conclusion as to the probable cost 

 in the latter can be drawn from it. At best it seems 

 rather a roundabout way of solving the question : first, 

 to allow coal dust to accumulate ; secondly, to cover it or 

 mix it with inert dust ; and, finally, to have to remove the 

 mixture when the accumulation ibecomes so great as to 

 commence to impede the traffic. 



The '' Microscopical Investigations " described in 

 chapter ix. refer to the microscopical examination of 

 grains and aggregations of coked coal dust, grains of other 

 matter, and fragments of fibrous substances that have 

 been subjected to a high temperature, and are accom- 

 panied by twenty full-page beautifully coloured illustra- 

 tions, which remind one more of a birds '-egg book than 

 of^ a serious treatise relating to a subject connected with 

 mining. It is not easy to see how these investigations 

 are likely to affect the question one way or another, but 

 possibly the committee may be able to extract some 

 information from them that does not appear on the 

 surface. 



Chapter i. of part ii., written by Dr. Wheeler, the 

 accomplished chemist and physicist attached to the testing 

 station, entitled " The Mode' of Propagation of Coal-dust 

 Explosions : Introduction," purports to " record the main 

 facts that have been established regarding the mode of 

 propagation of coal-dust explosions," but does not deal 

 with anything specially new or original. 



The second chapter of part ii.-, and the appendix on 

 " Experiments with Welsh, Scotch, and South African 

 Coals," have been already referred to so far as seems t 

 be necessary in the present place. 



The volume concludes with lists of the illustrations and 

 plates, and an index to the subjects, and is, as a whol'^ 

 most creditable to the publishers. W. Galloway. 



EXPLORATIONS IN NEW GUINEA. 



A T the meeting of the Royal Geographical Society on 

 January 30, Dr. H. A. Lorentz gave an account of 

 his latest journey in New Guinea, in the course of which 

 he succeeded in reaching the snow-covered peaks of the 

 main range. Much interest attaches to those regions in 

 the tropics where perpetual snow occurs, with their 

 transitions from the luxuriant vegetation of the equatorial 

 zone to the scanty flora of the snow-line, which on the 

 slopes of Wilhelmina Peak was reached at an altitude of 



