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THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[Aprilj 



good in this way ; they can get in again to the same tlioroughfare ; then, 

 when they have gone a certain distance, tliree or four boards— or ways, as 

 they call them— Ihey then begin to remove away the pillars, leaving nothjng 

 behind them. Supposing you ivere to take these pillars from the middle of 

 one of the passages, working it all round,— they begin at this coal ; they cut 

 away a width, remove it, and prop up the roof with timber. Remember, 

 that they are working at no greater height than this, in a vein of four feet 

 six inches deep. The man is never higher than this in that part, where «e 

 have gone for eight hours at a time, in a stooping position, looking up and 

 down at the black walls around us. Then they cut away this and prop up 

 the roof ; that is, they cut away the coal here, and leave an open space. 

 They cannot, however, afford to lose the timber which s\ipports this roof; 

 neither would it be desirable to continue 100 acres of roof over their heads in 

 that manner ; and such is the extent of the mine, or something like it; they 

 cannot leave that all remaining. It is, therefore, necessary to take away these 

 props, and then let down the roof above it. Whilst the props are there, the 

 coal being gone, it is called " a jud." You may have heard of " Williamson's 

 iud," during the recent proceedings; that being the place where the fire ori- 

 ginated by which the men were killed. Having taken away the coal, and 

 also the props of the jud, it is then left to itself, and almost immediately, or in 

 a very short time, the roof falls down under the rocks, which extend 900 fee' 

 above them, by its own weight. Having done this, they then go to the un- 

 broken coal, so as to ramify and get farther out into the space underground ; 

 thus the goaf increases gradually after them. It is to this particular part of 

 the mine that I wish especially to call your attention. I have explained to 

 you what the pillars are, and also the juds, and that upon these being 

 removed they fall down ; so that you understand that a goaf is only an accu- 

 mulation of these juds, after the props— either timber trees or wood— are re- 

 moved. I have also here given you on this board something like a notion of 

 what a goaf would be. It must be a concourse of ruins, smaller or larger, 

 according to the working of the mine, in the middle of the works. Imagine 

 this to be a vein of coal, or w.iys, left behind in working it; in this part, 

 where the pillar and jud have been drawn away, down falls the roof to a i:er- 

 tain height : we cannot tell how much. It makes a mass of ruins, over which 

 there is, of course, a Very irregular cavity which contains it. You may con- 

 ceive what the effect would be of a kind of mountain like this going in. When 

 1 use the term, " mountain,'' I am not far out. In this mine the goaf is thir- 

 teen acres in extent, in reality one and a half times the size of Lincotn's-inn- 

 fields. Such is the extent of the goaf I am speaking of to-night, where this 

 accident happened. This jud itself, therefore, must be rather larger in size 

 than the great pyramid m Egypt. Whether it goes up in the same angle we 

 know not at all ; but the degree of the angle where we crept to it was, as far 

 as I recollect, what 1 have taken here, which would be the same kmd of 

 thing, supposing it was very much cut out and in, which is the character of 

 a goaf. As this settles down into masses, not quite so compact as the rocks 

 before, it is very likely that here and there the roof rests on the goaf. Men 

 have crept up these cavities, and gone a certain distance on the top of the 

 goaf, as they call it. A friend of mine has been up in this very goaf I am 

 speaking of, at Haswell, creeping some ten or twelve yards over the blocks 

 of stone, and getting into it. There is great risk in doing this, unless a man 

 knows what he is about, because a fall having taken place here, another faU 

 may take place, and you may be there at the time. We ourselves had rathe"^ 

 interesting experience of the manner in which these things take place, for 

 while we were there, a fall of this description actually occurred, and cut us 

 off from each other. Mr. Lyell happened to be a little in advance of the spot 

 where it occurred, and I a short way behind. He heard the noise, but I saw 

 the effect. But the interest of the coal owners and men is such that they do 

 really venture up into these goafs at times when it is not safe to do so. Re- 

 member, then, that this goaf is a loosish mass of ruins, always, of course, 

 having a vacant space in it, about equal to the amount of coal taken away : 

 for you must bear in mind that all this ground was once solid. They have 

 taken away coal equivalent to this space. The rocks fall down ; and until 

 the surface of the ground begins to settle, there must be a vacant space in the 

 goaf somewhere or other of equal amountjto the coal taken away. Think of the 

 thickness of a block, equal in magnitude to that extent over a surface of thir- 

 teen acres, and that space left unoccupied by solid matter in this one goaf. 

 There are some mines at Newcastle, or in the neighbourhood, with very large 

 goafs ; the largest that I have heard of is ninety-seven acres. Imagine 

 ninety-seven acres in one mountain of ruins. This is the largest cavity w hich 

 we have heard of in that neighbourhood. There are others whicli are very 

 large at Whitehaven, in Lord Lonsdale's mines, but 1 must not go into that 

 subject. 



The point I wish particularly to call your attention to is the relation of the 

 goaf to the fire-damp, which is the real subject I desire to bring before you. 

 Fire-damp is hydro-carbon gas, a compound of hydrogen and carbon, formed 

 during the production of coal. Those are part of the organic matter in its 

 present state, and are retained in the coal under these circumstances until 

 apertures are made for its escape. This gas mixing w ith the air of the mine 

 piak«s an explosive mixture. For the purpose of representing fire-damp, I 



intend to night to use coal gas ; which is not a bad substitute for that ex- 

 plosive matter. It is a gas which burns more brightly and powerfully than 

 fire-damp, gives more light, contains a greater quantity of carbon, and fires 

 sooner. In these respects it differs from, but in others it agrees very well 

 with, fire-damp. In no one point are the existing differences material. In 

 all the points in which I have to consider it to-night it may fairly represent 

 coal-damp or fire-damp. 



The first thing which 1 point out to you, then, is this fire-damp, which, 

 «heu mxed with the air, forms what we call an explosive mixture. I will 

 show you what its nature is. If I take a jar, which now contains air only, 

 and mix a certain amount of coal gas with it, it will soon give you a notion of 

 the kind of explosive mixture formed in the mine. I have here a little mea- 

 sure, (lines marked upon this jar,) by which I can tell when I have six, seven, 

 eight, or nine volumes, if I may so term them, of air. At present there are 

 about six, and I will use that number. Now, if I take a volume of this gas, 

 as well as I can, and mix it with air, I have no doubt you will see the ex- 

 plosive mixture formed by the combination of fire-damp and air. (The lec- 

 turer proceeded to mix coal gas and air, and proved its explosive nature.) 

 This is perhaps one of the most explosive mixtures which can happen in a 

 mine from fire-damp ; for the proportion of gas and air is stronger than would 

 usually be found there. One of gas to five of air, or one of gas to fourteen 

 of air will form an explosive mixture, or any numbers between the two ; but 

 either less or more will not effect tlie object. When this gas is burning the 

 products resulting are water and carbonic acid. If I burn a portion of gas 

 in this way I can very soon show you both the water and the carbonic acid. 

 (Burning some gas under a glass.) You will there see the evidence of the 

 water at once ; for the moment I place this glass over the lamp I shall have 

 the water produced by condensation. You perceive that the glass is even 

 now becoming quite dim, not with dirt, but with water produced by the gas ; 

 the hydrogen combining with the oxygen and forming water. As the com- 

 bustion proceeds more and more water is formed. Besides that, I have here 

 also carbonic acid, which I will prove to you by putting in a little lime water, 

 which, upon being shaken up with it, immediately becomes milky in appear- 

 ance. You have now before you a proof of the two things evolved from the 

 gas, the milkiness evidencing the presence of carbonic acid, and also the water 

 produced from the combination of the gas with the air. The effects which I 

 have now shown you from experiment are the same as those which take place 

 from the combination of the fire-damp with the air conducted into the mine. 

 I need not take up your time by pointing out the fact that the same effect is 

 produced by respiration. You will take it for granted that when the air is 

 breathed exactly the same change takes place as when gas is burnt. I merely 

 mention the circumstance to point out to you, that as in breathing the air we 

 cause it to become of a bad quality, so thc.same effect is produced in air burnt 

 in combination with gas, whether fire-damp 'or coal gas, it will make the air 

 as had for breathing as though it had been breathed itself. I will take this 

 jar and breathe into it, and when I throw the air from my lungs into it you 

 will see how bad it is. The^air which is now in this glass is so bad that it 

 will extinguish a light. It is now unfit to breathe, and so also is the air com- 

 bined with the coal or fire-damp in the mine. (The lecturer showed these 

 effects by experiments.) This is one reason why so many lives were sacri- 

 ficed, and the accident was so extensive, by the recent explosion at Haswell 

 colliery. The circumstance of the combination to which I have referred in 

 the mine produces the very same kind of bad air as produced the explosion I 

 showed you from the mixture of coal gas with air, which certainly seemed a 

 very tame explosion. Before we went down Into the mine in the first instance 

 it was exceedingly difhcult to account for so large a number of deaths as 

 ninety. five taking place, when, from the report of men who had come out of 

 the pit only an hour or two before, there was little or no gas in the mine. 

 Miners who had only come out about an hour and a half before the accident 

 gave evidence before us that there was no gas in the mine. It was therefore 

 a difficult thing to account for the deaths of so many persons. Some of 

 these unfortunate individuals were burnt, but a great many were not ; the 

 former evidently died from burning and suffocation, the latter from suffoca- 

 tion only. 



I will show you a little experiment which illustrates the manner in whicli 

 when a fire does happen in a mine, the evil increases and grows up to 

 a most enormous extent. You see I burn this gas fairly, merely giving it an 

 opportunity of ifiixing with the air gradually, and so, getting the right and 

 just proportions, it burns very brightly ; but if I mix it with air first— which 

 is always the case in a mine— it does not bum in the same character. I have 

 here a lamp of wire gauze, upon .Sir Humphrey Davy's principle ; it will not 

 allow the flame to go through ; it nil! allow the air to go in and the gas to 

 go out ; consequently, if I let the gas into this wire gauze, it will mix very 

 much in the same manner as it does in the mine before the miner by accident 

 sets fire to it. In setting a light to this, I shall, therefore, have a very dif- 

 ferent effect to what I had before. You perceive that I have now a combina- 

 tion, not of air only, but of air ami gas burning together; this would explode, 

 were it not that the wire gauze prevents any such consequence taking place. 

 Yfe see here the combinatioa which takes place oi coal-damp and aic down 



