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them. Many valuable works have been written on Mines and Mining by men of talent, but many such works are not well understood by miners, who are generally not well educated. The author, having had a practical knowledge of mines and of miners from his youth, has, therefore, a better knowledge of what miners require for their better information. The object of his writing the following pages on mines, by way of a conversation between father and son, has been to make use of such words, and in such a manner, that the subject can be perfectly understood by miners. If the end for which the author has written be accomplished, his labour and expense will not be in vain.

ST. HELENS, LANCASHIRE,

April, 1864.

A CONVERSATION ON MINES.

The Nature and Quality of Gases.

Son: As you have been in mines, father, from early life, and your ancestors also had for generations past, a practical knowledge of them, I shall be glad, when convenient, to have a little conversation with you on mines.-Father: If only I can give information by which you and the public will profit I shall have great pleasure in so doing; and as we have a little leisure time just now, I shall be glad, and will endeavour, to answer to the best of my abilities, any question you require information on respecting mines and mining.

Son: Very good, father. Then I wish to know if carbonic acid gas, which miners often call black-damp, and gas left in mines after an explosion, be one and the same in quality?— Father: No. Gas left after an explosion is much lighter than black-damp, or even common air, as the said gas will make its way up to the roof, whilst black-damp will lie near the floor.

Son Have you experienced the effects of these gases; some people say they have a choking nature?-Father: I have often been affected by the gases, and have had to be brought home, having been rendered insensible by them, yet, I never felt the choking sensation that one would expect.

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Son: Had you much pain, just before you were struck insensible; or you remember very little of what took place?— Father: I remember well; I had no pain, and I was very sick for may be a moment, just before I lost all knowledge of things. My limbs also felt very heavy.

Son: Would you then be like a person insensible with sleep; as a person knows not the moment they pass away into sleep, I presume you in like manner would have no knowledge of the time, and moment, you passed into insensibility. But how long were you in that state of unconsciousness?— Father: I cannot tell how long I was insensible, as I was at home, brought up out of the pit, when I came to a proper knowledge of things; and when at home, long before my knowledge of things returned properly, every person I could see appeared as in a dream.

Son: By this, I presume, father, all persons lost by explosions, with after-damp, will suffer very little at death, as they will pass away like a person in a sleep?-Father: I believe they know very little until death pass them away into eternity; as I know had I remained in the pit a little longer, I should have passed away without a knowledge of the case.

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Son : Will explosive gas ignite if not mixed with atmospheric air?-Father: No. One foot of explosive gas requires a mixture of from five to twelve feet of air to cause it to ignite.

Son: Do not miners' candles burn with enlarged flames, when working where explosive gas accumulates ?-Father: The flame of the candle is enlarged when air and gas is near the explosive mixture. When one foot of gas is mixed with only 13, 14, 15, or 16 feet of air, the candle burns with

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enlarged flame; but by mixing more air to the one foot of gas, the flame of the candle diminishes to its proper size.

Son: What quantity of air does gas require to make it, when ignited, at the greatest explosive mixture or power?Father: One foot of gas mixed with seven feet of air will be near the greatest explosive mixture.

Son: If a miner's working place is full of gas, will not air annihilate or destroy the gas therein if mixed with it?— Father: No; air will not destroy gas, but only render it harmless by a larger mixture of air than gas.

Son Is explosive gas elastic?-Father: Yes. Three feet of gas may be pressed into the space of one foot; and, if the pressure be reduced sufficiently, the three feet will expand into six feet or more.

Son: Then when the weight is reduced from the gas, the gas expands out of the strata-out of every hole in the roof, and out of old gobs, which may be called magazines of gas, and overflows into the workings and tramroads from every place wherein it is compressed ?-Father: Yes; that's the cause of mines accumulating more gas at one time than at another, and also more when a change takes place in the weather.

Son: Why does explosive gas make its way up to the roof in mines, and fill holes and stock-working places which lie highest?-Father: Because explosive gas is much lighter than air. Two feet of the gas will weigh only a little more than one foot of air.

Son: Why does carbonic acid gas, which miners call black-damp, lay nearest the floor in mines?-Father: Because it is heavier than air. One foot of black-damp will weigh very nearly two feet of air, its greater weight being the cause of its laying nearest the floor.

Son: If damp be heavier than air, how can air drive it away, or force it along through the workings and up the upcast? Will not air pass through, and the gas settle downwards to the bottom like mud in water?-Father: Unless air pass through the workings and up the up-cast with such a velocity or speed, as to have a force greater than the weight of black-damp, it will settle downwards through the air like mud in water, and not be got up out of a mine.

Son: What is meant by generating, producing, and accumulating; that is, what am I to understand, father, by the same, as I often hear people say mines generate, produce, and accumulate gases?-Father: What you may understand by the word "generate," is to produce from, to bring from, or, to cause. Also, the word "accumulate," is to add to, to produce, to multiply, to increase, to collect, or, to make more.

Son: But how are gases then, father, generated, produced, or accumulated in mines?-Father: There are two ways by which gases may be said to accumulate in mines. All gases are generated or produced, you know, from every stratum, from one end of the whole route of the air-passage to the other. When the air first enters the air-gate, at the down-cast, there is in the first yard of its route a supply of gases. More gases are added to the same as the air passes onwards. Pass the air forward, and the quantity of gases in it multiplies; yet, as the air goes onward, the flow of gas from every stratum increases, until the same is discharged at the top of the up-cast. This is one way by which gases accumulate; but, the other is, when air cannot get at and around any stocked or undisturbed parts of the mine to bring gas out and away therefrom; and also when or if the air in mines should, at any time, be

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