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THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



241 



GASES AND EXPLOSIONS IN COLLIERIES. 



Tlie following interestinj: document is the report of a commission ad- 

 dressed by L"rd Linroln to Sir H. De La Berlieanil Dr. Lyon I'iayfaii-, for 

 tlie purpose of obtaining information as lo llie best means of preveolius, or 

 niiiiRatins, tlie fatal eiiVcts wliicli are so frequently the reiult of the gene- 

 ration of noxious gases in coal mines : — 



My Lord, — Havinj, in conformity villi the instructions contained in t!ie 

 E«rl of Lincoln's letter of the 27ih of August, 1815, directed our attention 

 to the composilion of the gases evolved from coal beds, lo the mode of ven- 

 tilating collieries, and to the subject of explosions in them generally, we 

 have the honour to submit the following statement for consideration. 



With respect to the gases evolved from beds of coal, they may be viewed 

 as the result of the continued decomposition of the vegetable matter from 

 whicli coal is derived, a decomposition which may be regarded as still in 

 progress under favourable conditions. Omitting the mineral substances. 

 which, when burnt, are known as ashes, coal is essentially composed of 

 carbon, oxygen, h\drogen, and nitrogen; and the quality of the coal de 

 penfis upon the relative proportion of these ingredients. When the propor- 

 tion of the carbon to the oxygen and hydrogen does not exceed about 75 

 per cent, the coal, in common terms, is called "bituminous;" when the 

 carbon amounts to about 8) or 90 per cent, it is termed " anthracite," or 

 stone coal : or, in other words, the most advanced state of decomposition 

 of the original vegetable matter bears the latter name. 



During the decomposition a portion of the carbon is removed by its union 

 with oxygen, forming carbonic acid, and another portion by combining 

 with hydrogen, as carburetted hydrogen. Thus by continued decomposi- 

 tion the carbon gradually becomes a more important constituent in the re- 

 maining part of the original vegetable mass. The change from bituminous 

 coal to anthracite can be produced artificially, and in a manner to illustrate 

 the subject, considered geologically.* 



Though carbonic acid is, no doubt, found in many of our collieries in 

 such a manner as to show it to be derived not only from the lights, horses, 

 and workmen employed, but also to be partly the result of the progressive 

 decomposition of the coal, it is with the carburetted hydrogen, or firedamp, 

 as it is termed, that the collier has chiefly lo contend. This comes upon 

 liim in various ways. Some coals more readily emit it than others, and 

 hence they are locally termed fiery seams, beds, or veins. From some coals 

 it would appear to escape more generally from the mass of the bed than 

 from others, the gas gradually accumulating from the discharge over a 

 wide surface. Other beds, again, are more fiery in the softer than tlie 

 harder portions, and where joints or fissures are common. M'hen two or 

 more seams of coal, having different qualities, make up a workable bed, 

 one will sometimes be more fiery than the other. Again, much depends, 

 all other circumstances being equal, upon the kind of roof or covering rock 

 of a coal-bed. If this be sufficiently porous, as many sandstones are, the 

 conditions for the escape of the firedamp upwards through superincumbent 

 rocks are more favourable than where the roof is composed of clay or ar- 

 gillaceous shell. 



The dislocations of the strata termed " faults" or " troubles" act fre- 

 quently also as channels for the passage of the firedamp into the works, as 

 they conduct the gas from coal seams beneath, yvhich may be highly 

 charged with it, although the seam underwork may be free.) 



Although we may regard a large proportion of this gas as previously 

 fo'nted, and ready to escape when the necessary conditions, sucii as those 

 of colliery workings, present themselves, we can scarcely suppose that 

 carburetted hydrogen is not also formed during the time occupied by the 

 progress of Ihe same workings, much being evolved from the older portions 

 of tiieni. The manner in which splinters of coal are thrown off during the 

 cutting of some beds has led to the hypothesis that the gas may be present 

 in a liquid slate, produced by condensation, so that when the needful pres- 

 sure is removed during the progress of the work, the sudden expansion of 

 the " fire-damp" from a liquid to a gaseous form throws oft' the fragments. 

 The force also with which the gas bursts suddenly fonh from clefts or 

 joints in some beds of coal is so considerable as to prove much previous 

 compression, particularly when those bursts or blowers last only for a short 

 time. When they continue for prolracteil periods, we may infer a more 

 constant supply from continued decomposition of the coal, though the first 

 sodden burst would point to compression. It has been inferred that Ihe 

 small cavities in yvhich the fluid gas is confined can be detected by the mi- 

 croscope in some coals. It is probable tiiat soft places, the sitles of joints 

 and fissures, and the walls or faults, are more favourable to the decomposi- 

 tion of the coal than its more solid poriions. 



The escape of fire-damp is generally influenced by the barometrical slate 

 of the atmosphere, especially yvhen much of the gas has become accumu- 

 lated in the wastes or goafs. This is more or less experienced in all pits; 

 but one striking case was pointed out to us by Mr. Jobliiig, of Jarrow Pit. 

 In a pit of which he is the viewer the gas issues from cracks in the roof of 

 the seam, and in low stales of the barometer is evolved in considerable 

 quantity. When the barometer is high, instead of this issue of gas, there 

 is a sensible current of air which enters into the cracks. When this in- 

 ward current takes place the pit is worked with naked candles, but when 

 the evolution of fire-damp commences Davy's lamps are employed. 



Assailed in this manner by a gas which, when mingled wilh atmospheric 



* Specimens in illustration of this, made by coking coal in a very ^adual monuer, are 

 lieposised in Che Museum of Ecoaomic Geoiogf. 



air in certain proportions, is highly explosive, a knowledge of its exact 

 composition becomes a subject of great importance lo the collier, since 

 ell'ective precautionary measures, more especially as regards the lights em- 

 ployed, must necessarily depend upon such knowledge. 



Dr. Henry, Sir Humphry Davy, in this country, and Bischoflfand othen 

 on the continent, have examined into the nature of the explosive gases of 

 mines, but wilh results differing from each other; for while the English 

 chemists found them to consist of carburetted hydrogen, with litde or no 

 admixture, the continenlal chemists have described Ihem as very complex, 

 mixtures of olefiant gas, carburetted hydrogen, carbonic oxide, hydrogen, 

 nitrogen, oxygen, and carbonic acid. On such a point ignorance would 

 be culpable; and we were instructed lo bring our knowledge up to the 

 present advanced stale of chemical an.ilysis. Whilst we were engaged in 

 this research. Professor Graham made a report to the Chemical Society on 

 the sa'iie subject. The previous invcsiigations of this chemist had render- 

 ed him well filled for the task, and Ihe results of his inquiries (according, 

 as they do, with our own) amply guarantee that the subject, as far as re- 

 lates to this country, may noyv be considered as decided, and show that 

 the importance of an exact determination had simultaneously engaged the 

 attention of the public. 



It is unnecessary to describe in detail the methods which we pursued in 

 the analysis; it may be sufficient to state that we adopted the methods 

 mentioned in a report to Ihe British Association on the analysis of gases 

 by Professor Bunsen, and one of us. We may, therefore, at once tabulate 

 our results, merely slating that we have devoted much attention lo this in- 

 vestigation, so a« to remove doubt upon a subject so important lo the in- 

 terests of Ihe public. The gases were collected in various ways, some from 

 blowers, others from the freshly exposed surfaces of the coal while the gas 

 issued out wilh a singing uoise, others from the explosive atmospher* of 

 pits. 



The general result of this examination is, that the only inflammable con- 

 stituent present in the explosive gas of collieries is carburetted hydrogen or 

 fire-damp ; there is not a trace of olefiant gas, and only in one out of Ihe 

 eight gases analyzed is there hydrogen. It follows from the previous 

 analysis that Ihe issue of fire-damp into the atmosphere of a mine must de- 

 teriorate the air, by adding an undue proportion of nitrogen gas ; in one 

 case this gas amounts to 21 per cent. During an explosion the oxygen 

 necessary to the respiration of the workers is removed by uniting with the 

 carbon of the fire-damp, and thus producing carbonic acid, a gas most fatal 

 to animal life. This carbonic acid, mixed with Ihe residual nitrogen of 

 the atmosphere, and that present in the explosive gas itself, forms what is 

 termed after-damp, which produces eflecis more fatal even than those aris- 

 ing from the explosion. It often happens, that after an explosion a sulh- 

 cienl quantity of oxygen remains to support the respiration of those wh» 

 survive its effects, were it not for the presence of carbonic acid. This gas, 

 when present in no greater pi oportiou than one or two per cent., is capaljle 

 of producing Ihe most injurious efiects. It has therefore been snggcsicil, 

 that cheap mixtures, made of substances capable of ab.sorhing carbonic 

 acid, such as glauber salts and lime, would prove useful to those who try 

 to aid the suflerers after the explosion. Such a mixture placed in a coarse 

 bag and applied to the mouth would elfectually absorb the carbonic acid, 

 and prevent it exercising an injurious effect on respiraiion. Certainly the 

 want of some such precaution in the case of Ihe Jarrow explosion causeJ 

 the death of a very meritorious man Jacob Uifty, Ihe overman of the pit. 



An explosion is, however, generally attended with much more complex 

 results than those described as attending the combustion of carburetted 

 hydrogen. The amount nf fire damp which may be first ignited may be 

 trivial, and yet produce the most disastrous efiects. From its lightness it 

 accumulates at the upper part of the passages, and diffuses with consider- 

 able difficulty, often acting as a train, and comniuuicaling the explosion to 

 the pent-up reservoirs of gas in the goafs. It is thus that in almost all ac- 

 counts of explosions two are generally described as taking place ; Ihe tii-l 

 local, and at the seat of the explosion ; the second more general, and aideii 

 by any accumulation of foul gas in oilier parts of Ihe pit. In the case nt 

 .1 arrow. Ihe heat attending the explosion was so intense as lo have thoruin>bly 

 cukeU to the de^ih oi nearly one quarter uf an inch the cual lining part ul 



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