Jandaby 1, 1900.] 



KNOWLEDGE. 



in its effects than those of the lightning and the earfcii- 

 quako, long defied investigation even as a scientific 

 phenomenon. An element of destruction, apparently 

 uncontrollable by human power, had to be grappled 

 with and subjugated so completely as to be put under 

 the management of the most uneducated miner. The 

 gas in many mines is constantlj' issuing from the coal 

 as it is worked, and sometimes emerges under great 

 pressure when the cavity containing it is punctured by 

 a pick or other means, the term " blower " being 

 applied to such an escape of gas. When mingled with 

 air, this gas forms a mixture which explodes violently 

 in contact with a naked light. 



By a pure inductive method Sir Humjjhry Davy 

 traced its history, step by step, until he fully made out 

 all itji characters. He discovered that fire damp in 

 reality requires a very high heat for ignition, the tem- 

 perature of red-hot iron or charcoal being insufficient 

 to inflame it. The gas was found not to explode in 

 narrow tubes, as these cool it below the point of igni- 

 tion, and a network of iron or copper wire is practically 

 equivalent to a series of sectional tubes. A lamp sur- 

 rounded by wire gauze was therefore used, and this 

 allowed a light to be carried into the mine with safety. 

 The destructive gnome of the mine was thus imprisoned 

 within a cage of mere wire gauze, and, vainly struggling 

 to escape, heated to redness the bars of its prison, thus 

 affording warning of the presence of the gas in danger- 

 ous quantity. Science, to its glory, by this simple moans 

 greatly minimised those scenes of death and heart-sicken- 

 ing misery which haunted the miner in his most peace- 

 ful hours, and has rendered comparatively safe an 

 occupation formerly one of dread and real danger. 



" Black damp," the deleterious constituent of which 

 is carbonic acid gas, is also evolved in coal mines, and 

 though incombustible and inexplosive, it is fatal to life 

 if allowed to accumulate to any considerable degree. 

 Elaborate systems of ventilation are therefore in us3 

 to carry off these gases so as to prevent undue accumu- 

 lation. Pure air is forced, pumped, or sucked down 

 one shaft, and vitiated air let out at another, both 

 shafts communicating with the surface, and the current 

 thus set up sweeps out the mine, so to speak, but the 

 " fire damp, " being lighter than air, is liable to 

 accumulate in inequalities of the roof and has some- 

 times to be dislodged by .special appliances. 



The main cause of death in explosions, however, is 

 not the explosion itself, but the " after damp " gene- 

 rated by it. Dr. Haldane, who visited Tylorstown 

 Colliery on the day after the terrible explosion there 

 on January 27, 1896, resulting in the deaths of 57 out 

 of 90 men in the pit, has shown that an examination 

 of the bodies revealed the astonishing and unexpected 

 fact that 52 out of the 57 deaths, that is, no less than 

 91 per cent., had been caused by " after damp," the 

 remaining five having been killed instantaneously by 

 violence. Of the men killed by " after damp," a post- 

 mortem examination showed that in nearly every case 

 the signs of carbon monoxide poisoning were present. 



The safety lamp, in its present improved form, if 

 carefully used, affords adequate protection, but it has 

 been found when the lamps are left in the miner's 

 possession and custody after he quits the mine, they 

 are sometimes damaged by careless handling, and taken 

 back into the mine in a defective and dangerous con- 

 dition, with appalling possibilities. By the Coal Mines 

 Act of 1896 legislation provided for the safe custody 

 of all lamps used in mines, the removal of any lamp 

 from the mine being forbidden. 



But there arc other sources of explosions in mines. 

 The primitive wedge, used from time immemorial for 

 detaching coal from the mass forming the seam, has 

 been superseded by the disruptive energy of explosives 

 — the so-called " shot " in blasting operations. A shot 

 improperly fired is called " a blown out shot," and the 

 initial cause of the explosion is the jet of flame pro- 

 jected by the blown out shot. When the " stemming," 

 or ■' tamping," used for confining the explosive within 

 the boring prepared for it is not sufficiently rammed in 

 to secure the complete internal combustion of the ex- 

 plosive, " a blown out shot " may bo pro(lut:e(l, and the 

 effect is to cause a jet of flame to issue with great force 

 from the orifice of the boring at the moment of the 

 shot, so that if " fire damp " be present in quantity an 

 explosion occurs and may extend throughout the mine. 



As some explosives arc unduly dangerous, the Secre- 

 tary of State, in accordance with the provisions of the 

 Act of 1886, has had drawn up a " Permitted List," 

 that is, explosives which owners of mines are required 

 to choose from as safest and best. At Woolwich 

 Arsenal there is a station provided with apparatus 

 designed to test the effect of firing explosives in pre- 

 sence of inflammable mixtures of atmospheric air with 

 either coal-gas or coal-dust. The charge of explosive is 

 fii-ed from a steel cannon with a uniform stemming of 

 dry clay, these conditions representing very closely 

 those of " a blown out shot." No exjjlosivc was con- 

 sidered to have satisfied the test if it caused more 

 than two failures in forty shots — a failure being either 

 an ignition of the gaseous mixture or an incomplete 

 explosion leaving a residue of explosive uncousumed. 



Another medium of disaster is coal dust, harmless 

 enough till the work of destruction has once been 

 started ; existing everywhere in the labyrinthine pas- 

 sages, as dust suspended in the air, it serves as a ready 

 distributor of flame and, therefore, explosion in all 

 directions from the local point of origin. It may be 

 seen in miniature when dry and dusty coal is thrown 

 on a fire from a coal scuttle, the finer coal dust is im- 

 mediately inflamed by contact with the glowing coals 

 in the grate, and passes up the chimney in the form of 

 a feeble explosion. 



Faraday, on scientific and experimental grounds, sug- 

 gested that coal dust contributed largely to the 

 devastating effect of an explosion. A zone of safety is 

 generally obtainable by saturating the dust in the im- 

 mediate neighbourhood of a contemplated shot. It is 

 estimated that the total number of shots fired in the 

 United Kingdom amounts to at least 2U,000,000 

 annually. 



Between 1851 and 1889, inclusive, there were 2,060 

 colliery explosions, and the number of lives lost was 

 8,859 ; during that period some 900,000,000 shots must 

 have been fired, giving a percentage of explosions to 

 shots of 0.000229, and of lives lost to shots of 0.000985. 

 In the decade ending 1882, the ratio of mortality by 

 explosions of fire damp was .65 per 1,000 persons, in 

 the next decade .32. In 1893 it was .29, and in 1894 

 .56. Lower still in 1895 — namely, .10, and up at .31 

 in 1896. In 1897, the first year in which the new Act 

 was in force, the ratio fell to .03, and in 1898 it had 

 risen a little— namely, to .05. The accompanying table 

 shows the number of persons employed underground in 

 coal mines and the output for the years given : — 



Year. Number of Persons Employed. Output in Tons. 



1896 ... 557,026 ... 208,503,868 



1897 ... 558,305 ... 215,145,025 



1898 ... 567,124 ... 215,161,954 



