59t> 



NATURE 



[June 29, 191 1 



The apparatus employed is similar to thai at Aliofts 

 .ind Li^vin. It includes 'a cylindrical gallery 6 leet 4 imhes 

 in diameter by 100 feet long, closed by means of a block 

 of concrete at one end ; with a cannon embedded in the 

 concrete, from which shots can be fired for the purpose of 

 raising and igniting the dust ; with small glass windows 

 at intervals of 6 feet 8 inches apart on one side ; with 

 arrangements for fixing paper diaphragms so as to isolate 

 certain portions of its interior when experiments with fire- 

 damp are undertaken, and so on. 



The coal dust is prepared by grinding and screening coal 

 of the following composition : — 



f'er cent. 



Moisture 1-94 



\olatile combustible ... ... 3S'" 



Fixed carbon ... ... ... • 57-73 



.•\sh 5-22 



loooo 

 Sulphur ... ... ... 1-25 



The method of conducting the experiments, and the 

 records of their results, are both so similar to those that 

 have been described in two previous reviews,' that it 

 would 1" ^tipi'ierogatory to describe them in this place, 

 more i >j)' rially as they occupy very little space in the 

 volume before us, and are, as has been said, mostly of a 

 preliminary character. 



The remainder of the volume is devoted to a history of 

 the subject, in which our author has done ample justice 

 to the work of his predecessors ; to dissertations on " The 

 Humidity of Mine Air," "Remedies for Coal Dust," 

 " Tentative Conclusions on the Dust Problem," and 

 " Special P""eatures in Dust Explosions," written by the 

 author himself, and includes special chapters on " Labora- 

 tory Investigations of the Ignition of Coal Dust," by 

 J. C. W. Frazer ; "Coal Dust Investigations at European 

 Testing Stations," by Axel Larsen ; " Exhaust Steam as 

 a Preventive of Dust Explosions," by Frank Haas; and 

 " Use of Steam and Water Sprays at Oklahoma Mines," 

 by Carl Scholz. 



All these subjects have already been investigated and 

 commented upon by other earlier writers, and as there is 

 nothing specially new or original in the articles before us, 

 they need not further detain us in this place. The fact 

 that the " selected bibliography " occupies twelve and a 

 half pages, and that the titles of no fewer than two 

 hundred and four of the papers and articles mentioned in 

 it contain either the word " coaldust," or in some cases 

 simply "dust" and "dusty," as applied to mines, 

 I xplosions, and experiments, is an indication of the grow- 

 ing interest with which the subject is, and has for some 

 time past been, regarded. Finally, considering the source 

 from which the present report has emanated, it is perhaps 

 almost superfluous to add that it is furnished with a 

 complete index. 



The Austrian experiments are being carried out under 

 the auspices of the Vienna Permanent Firedamp Com- 

 mittee, which decided to resume them in 1908 after an 

 interval of several years, during which operations at the 

 experimental gallery at Babitz, near Segengottes, had been 

 suspended. The ostensible object of this new series is " to 

 ascertain the conditions under which coal dust — especially 

 that of the Rossitz district — can be caused to explode 

 even in the absence of firedamp, and to test the means 

 hitherto employed, or proposed, for minimising or pre- 

 venting coal-dust explosions, chief among them being 

 water curtains, wet and dustless zones, and dry stone-dust 

 zones." " Experiments with coal dust in conjunction with 

 explosive gases are also in contemplation." 



The Babitz gallery differs from the others previously 

 referred to, first, in being built partly in masonrv an^ 

 partly in brick work, with an arch of 'the same materials 

 overhead, and a level floor ; and, secondly, in being whollv 

 underground. Its depth under the surface is 2 metres at 

 one end and 21-6 metres at the other. The thickness of 

 cover increases at a fairly uniform rate from the shallower 

 end to a distance of rather more than two-thirds of the 

 whole length, where it attains 7 metres, and thereafter 

 more irregularly to the deeper end. Its length is 2937 m., 

 and its other dimensions are : — at its deeper end, 1-3 m. 

 1 Nature, February 9, igti. vol. Ixxxvi., p. 223. 



NO. 2174, VOL. 86] 



wide at the sole, 1-4 m. wide at the spring of the arch, 

 174 m. high, and its sectional area 22 square metres; and 

 at its shallower end, 24 m. high and 34 square metres 

 in sectional area. 



Travelling communication is established with its interior 

 by means of three shafts, one sloping downwards to a 

 point 1-7 metres distant from its deeper end, provided 

 with stairs and ladders, and with a strong door both at 

 its top and bottom ; a second, sloping downwards to a 

 })oint 82 metres distant from the bottom of the first, also 

 provided with stairs and ladders, and with a strong door 

 at its top and bottom ; and a third, at its shallower end, 

 provided with a ladder only, and with its top capable of 

 being closed by means of balks of timber. 



The space between the bottom of the deepest shaft and 

 the end of the gallery nearest it (called the explosion 

 chamber) is built of concrete, and is 1-7 m. long, measured 

 in the direction of the axis of the gallery, 1-3 m. wide, 

 and I 82 m. high. Its open side next the gallery can be 

 <:losed by means of a paper diaphragm pasted to a 

 wooden frame fixed on the periphery of the gallery, and 

 coal dust and firedamp can be admitted to its interior 

 through two pipes, one for firedamp the other for coal 

 dust, which extend iito it from the surface. At 



distances of 47-8 metres respectively from the 



explosion chamber, two oilier pairs of pipes constitute 

 similar links of communication between the surface and 

 the gallery. One pipe of each pair serves for the introduc- 

 tion of coal dust, the other as an open passage in which 

 a shaft with a circular disc fixed to its lower end, which 

 is in, and just below the roof of, the gallery, can be 

 made to revolve rapidly by means of hand mechanism at 

 the surface. The coal dust, introduced through the two 

 pipes just referred to. falls upon the two corresponding 

 revolving discs, and is disseminated in the surrounding air 

 by the centrifugal force imparted to it by the motion of 

 the discs ; that similarly introduced into the explosion 

 chamber passes immediately into the interior of a small 

 vertical fan, made to revolve by means of an electric 

 motor, and is thus disseminated through the air in the 

 chamber in a similar manner. 



The gallery is lighted by means of shielded incandescent 

 electric lamps standing in niches in the walls, and is 

 ventilated 'by means of an electric fan fixed in the shaft 

 farthest from the explosion chamber. The fan is capable 

 of exhausting 20 cubic metres of air per minute from the 

 interior of the gallery. 



The coal dust employed in the experiments is collected 

 in the screening sheds (?) and in the workings, and only 

 the most suitable kinds are taken. Amongst these, the 

 finest leaves a residue of 3-8 per cent, on a sieve with 

 3480 meshes, and the coarsest a residue of 19-5 per cent, 

 on a sieve with 1160 meshes per square centimetre. Its 

 composition is as follows : — 



Per cent. 



Moisture ... ... 058 to 4-5 



Volatile matter ... ... ... 19-20 to 228 



Ash 9-17 



When an experiment is about to be made, coal dust is 

 strewn about in the gallery, or placed on a series of seven 

 narrow shelves equally spaced above each other, sup>- 

 ported horizontalh- (and transversely as regards the 

 gallery) in rectangular wooden frames suspended at 

 intervals of 5 m. apart, or laid on slanting laths fastened 

 to the walls, or disseminated in the air by means of the 

 fan in the explosion chamber and the revolving discs 

 previously mentioned, or brought into the sphere of action 

 by any one or any combination of these means. 



The explosives employed for disturbing and igniting it 

 are cartridges of gelatine dynamite from 150 up to 300 

 grams, " for the most part hanging free." and fired 

 electrically with i-gram caps ; or 300 grams of black 

 powder placed loosely in a mortar with a bore of 450 mm. 

 long and 27 mm. in diameter, tamped with paper, and 

 fired with a fuse. In some cases the dynamite charges 

 are fired in the mortar. 



No account is given as to the position in which the 

 dynamite cartridges are hung, either as regards their 

 height above the floor or their horizontal distance from 

 the end of the gallery or chamber ; nor can we gather 

 where, or at what height, or at what angle from the hori- 



