126 



♦ KNOW^LEDGE ♦ 



[April 2, 1888. 



occlufled or imprisoned for ages, starts forth on breaking 

 down the coal, and may acoumuUxte to a dangerous amount. 

 So far as I have been able to learn, no coal-mine is free 

 from " fire-damp ; " in those that are worked with naked 

 lights, " blowers " of gas may occasionally be heard, and 

 seen when the men apply their candles to them, producing 

 great jets of flame by their ignition. 



Mr. Galloway has now satisfactorily proved that hydro- 

 carbon gas is by no means the only source of dangerous 

 explosions. Coal-dust mixed with air forms an explosive of 

 terrible potency, and in most of the great colliery explosions 

 it has been a serious factor, in some cases probably by far 

 the most serious. A small explosion of gas, which alone 

 would do no mischief, may operate by blowing up and firing 

 the dust in its immediate neighbourhood ; and this secondary 

 explosion may do the like furliier on, and thus the blown-up 

 dust may act like a train of gunpowder with the most 

 terrible results. The drier the pit and workings, the greater 

 is this danger, and as we descend to deeper and deeper 

 seams, dry workings become more and more common, and 

 thus the coal-mines of the future will become progressively 

 more and more dangerous. 



We read in pretty books about the miner's glow-worm 

 lamp, and a pretty picture is thrown upon the magic-lantern 

 screen of the lecturer, displaying a collier at work with a 

 bottle full of these pretty creatures hanging by his side to 

 cheer and guide him in his work. I doubt whether such a 

 pretty lamp ever existed outside of thei-e pretty books and 

 pretty pictures. It may have been tried, but, having kept 

 a few pet glow-worms for a couple of years in a fern case, 

 and watched their habits, I conclude that they would object 

 to being bottled in crowds, and would not waste their 

 ilhuuinating energies when thus imprisoned, especially as 

 they light up for the purpose of courtship only during a 

 short courtship season. 



The " steel mill " was really used. It was a wheel with 

 steel periphery, which, when raf>idly rotated with a flint 

 pressed against it, threw out a shower of sparks. These 

 gave sufficient light, but they were also capable of firing the 

 gas. I have illustrated that to a class by thrusting a 

 brightly-heated iron wire through a bladder containing a 

 mixture of hydrogen and oxygen gases, which thus treated 

 explodes instantly. The spai-ks of the steel mill are simply 

 incandescent particles of steel. 



The introduction of the wire-gauze lamp altered all this. 

 Herious explosions that occurred in Durham in 1812 led to 

 the formation of a Society for the Prevention of Accidents 

 in (Joal-miues. It was at a meeting of this society in Sun- 

 derland in 1813 that Dr. Clanny, of Newcistle, exhibited 

 his first lamp. He had worked upon the problems for some 

 time. George Stephenson, then a humble engine-wright at 

 the Killingworth Colliery, Newcastle, was doing the same, 

 and practically introduced a wire-gauze lamp in 1815. His 

 first lamp was ready on October 21, further improved on 

 November i, and fairly and practically in use November 30 

 at Killingworth under the name of the " Geoi'die Lamp." 

 I will not enter upon the controversy respecting the per- 

 sonal merits of the difterent inventors beyond expressing 

 my opinion that the merit of Davy was rather that of 

 demonstrating the rationale of the action of the wire gauz3 

 in resisting the passage of flame between its meshes than of 

 the invention of the lamp. There can be no doubt that too 

 much has been claimed for Davy, Smiles, in his Life of 

 George Stephenson, concludes that the illustrious chemist 

 and the humble engine-wright arrived by wholly independent 

 paths at a knowledge of the facts concerning the non-passage 

 of flame through tubes and small apertures. 



The principle upon which the efficacy of the Geordie or 

 Davy lamp depends may be easily demonstrated by lowering 



a piece of wire gauze upon a common gas flame. As the 

 gauze descends it will be seen that the flame does not pass 

 between its meshes, but is effectually extinguished when it 

 touches the metal. On applying a light to the upper surface 

 of the gauze another upper flame appears, which is evidently 

 a continuation of the partially-extinguished flame below. 

 The gas passes between the meshes, but the flame cannot. 

 Neither can a flame travel through cold metal tubes of small 

 bore ; but if either the gauze or the tube be made red-hot, 

 it no longer stops the flame. A further demonstration is 

 afforded by making a candle with a small thread wick, 

 and when the wick is lighted pas.sing over it a metal ring 

 with an opening equal to the whole width of the flame. 

 Although presenting no mechanical obstruction, the flame 

 is completely extinguished by the cold ring. 



The reason is very simple. The flame is due to the 

 energetic combination of the hydrocarbon gas with oxygen, 

 but this combination does not occur unle.ss the gases be 

 heated to a certain point. This heat, which is necessary 

 for the continu.ance of the combustion, is carried away 

 by the metal, which is a good conductor. The potency 

 of metal in carrying away the heat of a flame is well 

 shown by stretching a pocket-handkerchief, or piece of rag, 

 over the convex side of the bowl of a silver spoon, and 

 plunging the fabric into a gas-flame. It may be held there 

 for some time without being even scorched, but if the 

 experiment be repeated on a wooden spoon a hole is rapidly 

 burned in it. The flame of a jet that is issuing with some 

 force — as from a blow-pipe or Bunsen burner — may pass 

 through the gauze according to velocity of issuing gas and 

 size of mesh. Also, if the gauze is red-hot, its power of 

 obstructing the flame is lost. 



These facts indicate a limitation to the practical efficiency 

 of the miner's lamp. When surrounded with gas outside, 

 the space within the gauze is filled with flame, and this 

 warns the miner of his danger. But the warning may itself 

 be fatal if he becomes alarmed, and rushes forward too 

 rapidly, or sways his lamp cai-ekssly, and thus produces a 

 through current that shall blow the inner flame outward. 

 It is rarely that a human being is placed in a position 

 demanding more of true courage than that of the miner 

 when the flame of his lamp wick first elongates, then is 

 surmounted by a blue cap, and finally flashes into a lambent 

 flame that fills the lamp. He must hasten to the shaft for 

 his life's sake, for if he is too tardy the gauze will become 

 red-hot. If he rushes forward, or otherwise moves his 

 lamp with a speed exceeding 4 or 5 feet per second, he will 

 probably kill himself and all his comrades. In the midst of 

 this dilemma he knows that others are in the same position, 

 and that lack of courage and' coolness of anj- one may be 

 destructivo to all. 



A number of devices have been adopted to diminish this 

 danger, far too many for me to describe or even name here. 

 Double gauze, glass protection outside the gauze, as in the 

 " Geordie," are among these, and are more or less effective, 

 but none are perfect. My surprise is not that so many 

 colliery explosions occur, but that they are so few. The 

 flippant comments on the ignorance of the miners that are 

 so commonly made are really due to the ignorance of the 

 commentators. The old story of the man who was 

 descending a dangerous pit with a lighted candle on his hat, 

 and, when reprimanded, replied, " Well, arnt I got my 

 Davy ? " may amuse a magic-lantern audience, but those who 

 know the simple but .shrewd-minded colliers are amused ia 

 contemplating the self-sufficient silliness of the audience, 

 who can suppose that their fellow-men, who are daily carry- 

 ing their lives in their hands, are ignorant of the primary 

 conditions upon which their safety depends. 



It is true that familiarity with any danger induces a 



