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known as “ blowers” are liable to occur, because the discharge of gas from these is so sudden and so enormous as to overpower the most plentiful and perfect ventilation. In nearly all coals there is a risk, and in some a certainty, of meeting with these blowers, and for perfect security we must find some means of removing the danger arising from them. This is done by employing what are known as “ safety-lamps,” that is, lamps which may be carried into an explosive mixture of carburetted hydrogen and air without firing the compound. The principle on which they depend was discovered independently about the same time by Sir H. Davy and George Stephenson, and is as follows :—It was found that if a lamp or candle be enclosed in an envelope of fine wire gauze, containing not less than 600 holes to the square inch, any explosions which take place within the envelope cannot be communicated to the gas outside, and that the flame cannot pass through the gauze except under pressure.* In Davy’s original lamp the light is simply enclosed in a cylinder of this gauze, but this arrangement has a somewhat feeble illuminating power.- Modifications have been made by the introduction of glass, which give a better light; and other contrivances have been proposed for increasing the draught, and thus obtaining a similar result. The principal forms of safety-lamp are well described in the “Rudimentary Treatise on Coal and Coal Mining,” by Mr. Warrington Smyth (Lockwood & 00., 1872).

Unluckily, when perfect ventilation and an efficient safetylamp have been provided, the colliery manager’s cares are not at an end. The working collier is proverbially reckless, and nothing can prevent him from opening his lamp, if he can, to get a better light for his work, to light his pipe, or even sometimes from foolhardiness. Lamps are locked before being given into the men’s hands, and then the men carry keys. Lamps are constructed which go out directly they are opened, and then the men take down lucifers and light them again. Lamps have been devised which are locked with a plug of lead, on which a device is punched, and which cannot be opened without breaking the plug; and some such troublesome precaution, it seems, must be adopted, if tampering with the lamp is to be put an end to. The latest contrivance is a lamp which is closed by a steel spring, and can only be opened by the action of a very powerful magnet on the spring. The magnet is kept in the custody of the head manager, and as it is obliged to be a far more powerful one than the colliers are likely to be able to obtain, this plan, if it succeed in other respects, seems likely to be effective. '

‘ For an explanation of the physical reason of these facts, see Tyndall’s “ Heat as 9. Mode of Motion,” p. 240. "

A probable cause of accidents which we can only hint at here is the spontaneous combustion of the waste coal left in the goaf ; and it is also highly likely that some explosions have been caused by blasting in fiery pits.

It is further to be noted, that even the most perfect safetylamp requires occasionally the utmost caution in using it. In a fiery atmosphere the combustion and explosion of gas within the lamp sometimes raises the gauze to a red-heat, and in this way sets light to the explosive mixture outside. It has also been repeatedly proved by experiment that no lamp is safe in a strong current of air. The velocity necessary to cause an explosion varies with different forms of lamp, but all that have been yet devised blow up sooner or later, if the force of the draught in which they are placed is gradually increased.It ' Science has therefore still something further to do for the collier in the matter of lighting him at his work; and the most promising quarter, perhaps, to which the would-be inventor can turn his attention is the electric light. If this could be produced cheaply and in a portable form, we should have iii it all the conditions of perfect safety; for the light may be completely out off from the explosive atmosphere by surrounding it with a glass globe, and a cage of a few iron bars would guard against any risk of fracture to the glass. Even now it seems that this source of light might be usefully employed in these exceptional cases, like the first opening out of a colliery after an explosion, when much of the work has to be done in the dark. A beam of parallel rays sent down the shaft by an electric lamp at the top would have intensity enough to allow of its being reflected by mirrors into the workings, and would make the task of beginning to open out a wrecked colliery easier and more expeditious. And as soon as a cheap galvanic battery is invented, there seems to be no reason why we should not light our collieries with a brilliancy undreamed of now, and at the same time get rid of all risk of explosion.

We have not yet said anything about the means of detecting the presence of fire-damp, and since it is as true in a mine as elsewhere that to be forewarned is to be forearmed, this part of our subject must not be passed over. It has been noticed that many serious explosions have been preceded by rapid falls of the barometer, and it is not hard to imagine how sudden diminution of atmospheric pressure might well affect so light and easily moved a gas as carburetted hydrogen. Every colliery ought therefore to be furnished with a good barometer, and its readings constantly noted; and whenever a rapid fall takes

' Among the latest of these experiments are some made at the Barnsley Gas \Vorks. See “ Mining Journal," 1867, p. 530.

place, extra precautions should be used. Also, when a safetylamp is carried where firedamp is present, the flame elongates and takes a pale bluish hue, till the gas is present in quantity enough to cause explosion within the game. These indications enable a trained eye to estimate to a very fair degree of approximation the proportion of gas present. The observation of them partakes somewhat of the nature of playing with fire, and requires a cool head and steady hand, and a knowledge, which can be acquired only by practice, how far it is safe to go, and when it becomes necessary to withdraw or extinguish the light. A very beautiful and ingenious indicator has been invented by Mr. Ansell, the general principle of which is as follows :——A vessel full of air is separated from the impure atmosphere of the mine by a porous diaphragm. In virtue of the law of the diffusion of gases, air passes out and carburetted hydrogenpasses in through the diaphragam; but the latter, on account of its low specific gravity, is transferred in larger quantity than the former. Consequently the pressure within the chamber is increased, and either by the expansion of the elastic walls of the vessel itself, or by the raising of a column of mercury, an electric circuit is completed, and a telegraphic bell set ringing. If such instruments are placed at different points in the mine, and connected by wires with bells at some central station, the presence of gas in dangerous quantity at any place is immediately pointed out, and the necessary orders may be at once issued. In another form of the instrument, intended to be carried about, the gas passes by diffusion into a sensitive aneroid chamber, and moves an index in the same way as in the common aneroid barometer. Beautiful as these contrivances are, it is a question whether their construction is not too delicate to stand the rough life of a coal mine; but fair and ample trial ought certainly to be made of them. Their competency to detect the presence of gas has been proved by actual experiment, and the time may come—the average intelligence of the collier having been raised by education—when it will be possible to employ them as the inventor has suggested.

And now comes the question, How is it that though science has worked so earnestly, and as it would seem so successfully, to put into the miner’s hands the means by which he may protect himself from the dangers that beset him on all sides, the tale of lives lost year by year shows no signs of a decrease? To anyone who has studied the Reports of the Colliery Inspectors,

'the answer comes in no uncertain tone. The facts there collected show, without the possibility of a mistake, that a very large portion of the accidents ought never to have occurred, since they have been caused either by the incompetence of the managers or the foolhardiness of the men.

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On the first head, though there is still much to complain of, considerable improvement has taken place of late, and the establishment of such schools as the College of Physical Science at Newcastle, and the provisions of the Mines Regulation Act of last Session, will doubtless produce before long a still larger advance. But much yet remains to be done before those entrusted with the immediate superintendence of our mines can compare with the men holding similar positions in Germany. Of the recklessness of the men, one or two instances may be given to show that they are not accused without reason. In 1866 occurred the most disastrous colliery explosion yet on record—that of the Oaks Colliery, by which more than three hundred men’were in a moment laid lifeless; but even this warning had no effect, for only a few weeks afterwards some colliers in an adjoining colliery, working the same fiery seam, were summoned before the magistrate for using lucifer-matches in the pit to light their pipes with. It is indeed seldom possible to bring home to anyone the guilt of having caused an explosion, for those most at fault are usually the first victims ; but the constant occurrence of lamp-keys and lucifers on the persons of the killed tells a story which cannot well be misread. Totally untrained to reflection, and living face to face ' with danger till they have lost almost the sense of fear, these men deliberately risk their own lives, and those of some hundreds of their fellow-workmen, rather than forego the luxury of smoking for an hour or two. Another fact brings out this characteristic very forcibly. We have already shown that in many cases it is necessary, however perfect the ventilation may be, to use safety-lamps, because sudden outbursts of gas may any minute occur which will overpower the best ventilation in the world: in a word, that here as elsewhere it is good to have two strings to your bow. But while fully admitting the truth of this, many really intelligent managers are averse to the use of safety-lamps because the men cannot be brought to see the force of the old adage, and will insist on trusting to lamps alone, and neglect the ventilation.

Two things it seems to us can alone remedy this disastrous state of things. The rising generation of colliers must have impressed upon them some sense of moral responsibility, and they must be taught so much science as will enable them to understand how accidents are caused. Ministers of all religious denominations show a most praiseworthy activity after any colliery disaster, but they Seem to dwell mainly on the uncertainty of life, and the necessity for being prepared for death at any moment. Such warnings are not specially applicable to miners ; they might, for instance, be addressed with considerable propriety to anyone who nowadays has occasion to travel often

by railway. It might have gone some way towards preventing the disaster altogether if it had been forcibly insisted on beforehand, that a sin, whose magnitude can scarcely be eStimated, is committed every time a colliery proprietor employs an incompetent manager from short-sighted economy, or a collier lights a pipe in a fiery pit.

The second remedy is by no means difficult of attainment. Many of the larger collieries have already attached to them, by the generosity of their proprietors, excellent schools, and the example thus set will doubtless be extensively followed. If ' clear and simple lectures, illustrated by experiments, were given in these schools from time to time on the rationale of colliery disasters, the rising generation of colliers would grow up with quite enough of scientific knowledge to cure them of. the recklesSness which disgraced their forefathers.

That there is the mental grit in colliers which makes all that has been here suggested for their improvement possible, and a great deal more besides, no one who knows them well will for a moment deny, but they have not yet been shown how to turn it to account. With all their faults they are a hearty, shrewd race, and among them the writer has spent manya pleasant and profitable hour. ‘

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