430 



SCIEJSrCE. 



[Vol. IX , No. 222 



parts as well as on the floor. This fine dust is not 

 only found on horizontal surfaces, but it exhibits 

 the property of sticking to timber, stone, and coal, 

 something like soot hanging in a chimney, being 

 sometimes from one to two inches thick on ver- 

 tical and overhanging surfaces. In dusty mines 

 it is often necessary to remove the dust on the 

 floor of the roadvray to prevent the tracks from 

 becoming blocked ; but the upper dust is not in- 

 terfered with. Only one pound of dust to one 

 hundred and sixty cubic feet of air is necessary in 

 order to form an inflammable mixture, and this 

 proportion is often largely exceeded on dusty 

 roads. 



Coal-dust in mines is often referred to as con- 

 stantly present in the air. This is not so, except 

 to a limited extent. The velocity of the air is 

 rarely sufficient to carry dust any considerable 

 distance. When dust is largely present in the air, 

 it is due to some disturbing cause other than the 

 ordinary movement of the air. The rapid passage 

 of cars against the air-current raises a cloud of 

 dust from them ; the passage of men and horses 

 stirs up the bottom dust ; the hewer at the work- 

 ing face raises about him a thin cloud of dust ; 

 the concussion of a blast, or wave of air caused by 

 a heavy fall of stone, fills the air with dust ; but 

 in the absence of some such cause the dust is qui- 

 escent, and after its disturbance by any cause it 

 soon settles down again. The fine, soot-like, up- 

 per dust is, however, extremely inflammable, even 

 when not disturbed ; and after explosions the 

 greatest amount of violence is observed on those 

 roads likely, before the explosion, to contain the 

 most of this kind of dust. After explosions, the 

 dust thrown into the air and ignited is found to be 

 very generally coked. 



Not only has there been heretofore a general 

 misconception as to the nature of the explosive 

 substance, but also as to the actual cause of death 

 of the victims. This may occur fvova flame, force 

 of the explosion, falls of stone and timber, suffoca- 

 tion by dust, or after-damp ; but the evidence 

 goes to show that the immediate cause of death, 

 in almost all cases, is after-damp, i.e., the gases 

 resulting from the explosion. After-damp pro- 

 duced by the explosion of ordinary fire-damp 

 consists of carbonic-acid gas, nitrogen, and water 

 vapor ; and death results from slow suffocation, 

 due mainly to the exhaustion of the oxygen in the 

 air. 



But the after-damp from explosions of coal-dust 

 is much more rapidly fatal, and evidently con- 

 tains some more poisonous constituent. Analysis 

 shows that this is carbonic oxide. Miners fre- 

 quently work without serious inconvenience in air 

 containing so much carbonic acid as almost to ex- 



tinguish their lights ; but a proportion of carbonic 

 oxide so small as to have no appreciable effect on 

 his light will cause the death of the miner in a 

 few moments, sometimes almost instantly, his 

 light continuing to burn after his death until the 

 oil is exhausted. It has repeatedly happened that 

 miners who were outside of the roads traversed 

 by an explosion, and uninjured by the explosion 

 itself, have been cut off by the after damp, and 

 have perished in trying to force their way through 

 it to the shaft. In fact, the most serious features 

 of dust-explosions are, that, unlike gas explosions, 

 they occur absolutely without any warning, and 

 mainly near the shafts, thus preventing escape 

 from any part of the mine. 



Of six typical explosions occurring in the north 

 of England in the years 1880 to 1885, five occurred 

 in Durham, in dry dusty mines, and were un- 

 doubtedly dust-explosions. The total loss of life 

 was three hundred and thirty, or an average of 

 sixty-six for each explosion. The sixth explosion 

 occiirred in the Whitehaven colliery, which ex- 

 tends three miles under the sea, and is wet, and 

 free from dust. This was clearly and purely an 

 explosion of fire-damp, and the most extensive of 

 its kind within the experience of the Messrs. 

 Atkinson, and yet only four lives were lost. This 

 mine was not only free from dust, but the explo- 

 sion was limited to the most remote, deepest, and 

 most poorly ventilated portion of it. 



The following conclusions are warranted by the 

 study of these explosions : aU the explosions 

 were limited to one plane or level of the colliery, 

 in no case ascending or descending vertically so 

 as to continue the explosion on another plane. 

 The single gas explosion was remote from the 

 shafts, and so cut off from communication with 

 higher or lower workings ; while all the dust-ex- 

 plosions extended to or even crossed the down- 

 cast shafts, but could not follow the shafts up or 

 down because they are wet and free from dust ; 

 and, in general, the flame and violence of the 

 dust-explosions were confined to those roads on 

 which there was much coal-dust, their intensity 

 varied with the amount of dust, and they were 

 often arrested at places where the roads were wet 

 or damp. In no case were the return airways, 

 where gas is always most abundant, seriously 

 affected ; and the intake airways also escaped 

 where not used for handling coal. Since the dust 

 is naturally heavy and quiescent, it can only be 

 ignited when some disturbance throws a cloud of 

 it into the air in the presence of a flame. One of 

 the dust-explosions was probably initiated by a 

 small explosion of fire-damp ; but all the others 

 were simultaneous with the firing of shots of gun- 

 powder in stone ; and it is concluded that the con- 



