One of the chief dangers to which workmen in the mines are subject arises from the gases given off by minerals and metals. Though these deleterious gases are commonly found in more or less abundance in the coal mines, and are usually considered in connection with such mines, they are, nevertheless, not confined to the coal measures. They have been noticed also in mines of lead, sulphur, salt, and other substances. It is said that anthracite contains a much larger proportion of these gases than do bituminous or other coals, but that being hard it holds them more tenaciously, and is therefore worked with less risk. The soft coals, on the contrary, being porous as well as soft, allow the gases to escape from them much more readily, and so increase the danger at the working faces of the mines. The gas given out most abundantly by the coal is light carbureted hydrogen, known as marsh gas, from the fact that being a product of vegetable decomposition under water, bubbles of it rise to the surface on stirring the waters of a marsh. This is the gas that is known to miners as fire damp. The French call it grisou. Marsh gas, in its simple form, consists of four parts of hydrogen to one of carbon. It is about one half the weight of air, and therefore rises and gathers at the roof of a mine chamber, extending downward as it accumulates. When it is mixed with from four to twelve times its volume of atmospheric air it becomes violently explosive. If the mixture is above or below this proportion it is simply inflammable, burning without explosive force, with a pale blue flame. The value of a perfect ventilating current across the faces of chambers which are making gas rapidly can now be appreciated. It is not only necessary that the supply of air should be sufficient to make the gas non-explosive, but that it should be sufficient to dilute it beyond even the point of inflammability. For to its inflammable more than to its explosive quality is due most of the disasters with which it is accredited. A peculiar and dangerous feature of this gas is that it does not always escape from the coal at a uniform rate, but often comes out suddenly in large compact bodies. These are called “blowers.” They are found most commonly in faults, in cracks in the coal seams, or in open spots in the body of coal, where they have opportunity to accumulate. They contain, besides marsh gas, less than one per cent. of carbonic acid, and from one to four per cent. of nitrogen. It is impossible to anticipate their coming; the miner’s drill may strike into one and free it at any time without a moment’s warning. It may even burst through the face by its own power. In such cases danger is imminent, disaster is most common.

When the naked light of the miner comes into contact with any considerable quantity of fire damp in an explosive state the shock that follows is terrific. Men and mules, cars and coal, are hurled together to destruction. Walls are swept out, iron rails are bent double, doors are torn from their fastenings, the mine is laid waste. The damage which results from an explosion of gas is of course much greater than that which is due to mere ignition and burning without the explosive force. In the latter case, however, the danger to the miner is but slightly diminished. He is liable to receive injuries which may prove immediately fatal. His burning lamp no sooner touches the body of fire damp than it bursts into flame, which, propelled by expansive force, passes swiftly down along the roof of the chamber. Taking up enough oxygen from the atmospheric air to make combustion more fierce, it returns to the face of the chamber with a violent contractile surge, scorching everything in its path, and then, perhaps after another brief sally, it burns itself out.

The miner who accidentally fires a block of fire damp falls suddenly flat on his face on the floor of the mine, burying his mouth, nose, and eyes in the dirt to protect them from the flame and intense heat. Then he clasps his hands over the back of his head and neck to protect these parts from injury, and lies waiting for the minute or two to pass before the fire shall have burned itself out. But he must not wait too long. The fatal after damp follows quick upon the heels of the flame, and his only safety from certain death lies now in immediate flight.

The danger from inflammable gases was known and appreciated very early in the history of mining. But it was long thought to be an unavoidable danger. Light must be had or no work could be done, and the only light that could be obtained was from the flame produced by combustion. Candles were commonly used. They were stuck into a ball of clay and fastened to the sides of the working places at the most advantageous points. The bituminous mines of England were peculiarly prolific of inflammable gases; accidents were almost of daily occurrence. On the 25th of May, 1812, a great disaster occurred at Felling Colliery, near Newcastle, in which eighty-nine persons lost their lives by explosion of fire damp, and public attention and the public conscience were directed to the matter of safety in mines more intensely than ever. Sir Humphrey Davy was then in the zenith of his fame. In April, 1815, he returned to London after a triumphal tour through France and Italy, in which his progress had been marked by a series of brilliant experiments. He had no sooner reached home than he was asked by Mr. Buddie, a well-known colliery owner of that day, to turn his attention toward improved methods of lighting the mines. Specimens of the dangerous gas were sent to him from Newcastle, and he experimented with them. He found that the flame from them would not pass through a small tube, nor through a set of small tubes standing side by side. He found also that the length of the tube was immaterial. He therefore shortened them until they were mere sections, until his set of parallel tubes became simply wire gauze. The proper proportion between the substance of the wire and the size of the aperture was found to be twenty-eight wires to the linear inch, and seven hundred and eighty-four apertures to the square inch, a proportion that is still in use. This wire gauze was then made into the form of a cylindrical tube about six inches long and one and one half inches in diameter, with a flat gauze top. To the bottom of this tube was fastened a small cylindrical oil vessel, and to the top a ring handle. The wick extended up from the oil vessel inside the tube.

When Sir Humphrey had perfected his lamp to a point of safety he took it and went with Mr. Buddie down to Newcastle, and together they traversed with impunity some of the most dangerous parts of the Bentham seam, at that time one of the most fiery coal beds known. At about the same time the celebrated George Stephenson also invented a safety lamp similar in most respects to the Davy, so also, later, did Clanny and Museler, and all four kinds are in general use. Other styles have been invented also, but for the purposes to which a safety lamp is properly applied the Davy doubtless still excels all others. Those purposes are principally the investigation of workings to discover the presence of gas, and to aid in the erection of proper appliances for driving it out. It is not necessary, in these days of powerful ventilating machinery, to allow dangerous gases to remain in working places and to mine the coal there by the light of safety lamps. It is far safer, and better in every way, to sweep the chambers clean from foul air by strong ventilating currents, so that the miner may work by the light of his naked and most convenient common tin lamp. The objection, therefore, to the Davy lamp, that the light given out by it is too dim, need not be considered a serious one. The size of the flame cannot be increased without destroying the proportion between it and the gauze cylinder, and the size of the cylinder cannot be increased without making a dangerously large chamber for the accommodation of explosive gas. Therefore the light given out must, of necessity, be dim.

But the safety lamp itself must be used with care and prudence, otherwise it may become no less an instrument of danger than the naked lamp. When it is carried into a chamber that contains fire damp the gas enters freely through the gauze into the cylindrical chamber, and is there ignited and consumed without communicating its flame to the outside body. The presence of gas is indicated by the conduct of the flame of the lamp. If the percentage of marsh gas is small the flame simply elongates and becomes smoky. If it is mixed with from eight to twelve or fourteen times its volume of atmospheric air the flame of the wick disappears entirely, and the interior of the cylinder becomes filled with the blue flame of burning gas. It will not do to hold the lamp long in this mixture, the wires will become red with heat, and the outer gas may then become ignited from them. Neither will it do to hold the lamp in a current of gaseous air moving at a greater rate of speed than six or eight feet per second, since in that case the flame is apt to be driven through the gauze and to set fire to the gas outside. There is also danger if the lamp be thrust suddenly into an explosive mixture that the force of the explosion inside the wire-gauze cylinder will force the flame through the mesh. It will be seen, therefore, that even the safety lamp is not an absolute protection against danger from explosive and inflammable gases.

The position and duties of the fire boss at each colliery have already been referred to. He goes into the mine about four o’clock in the morning and makes his round before the men arrive. If gas has been found in an inflammable or explosive condition the workmen are not allowed to enter the place until it has been cleared out by the erection of brattices and other ventilating appliances. If only an insignificant quantity has been found in any chamber, the miner who works the place is warned of its existence and told to brush it out. In obedience to this order he goes to the working face, sets his lamp on the floor, and removing his coat swings that garment vigorously over his head, thus mixing and diluting the gas and driving it down into the current.

It is not in the working chambers, however, that the most dangerous accumulations of fire damp are found, but in the worked out and abandoned portions of the mine. Here it may collect unnoticed until large bodies of it are formed, and then when some one blunders into it with a naked lamp a terrific explosion is the inevitable result. The act of 1885 recognizes this especial danger, and makes it obligatory on operators to keep old workings free of dangerous bodies of gas; and to this end it directs that they shall be inspected at least once a week by the fire boss or his assistant. Where it is known that such gas exists, or is liable to accumulate in old workings, the entrances to such places are barred across, and the word “Fire!” is written conspicuously at the opening to them. But notwithstanding all rules and precautions, ignitions and explosions of fire damp are still dangerously common. Among the thousands of mine workers there is always some one who is careless, some one who blunders; the lessons of perfect watchfulness and obedience are hard lessons to be learned.

As has already been intimated, the danger which results from the burning of fire damp lies not alone in the fierce flame given forth, but also, and perhaps in a still greater degree, in the product of its combustion. This product is known to the miner as “after damp,” and consists principally of carbonic acid gas with some nitrogen. It is irrespirable, and a single inhalation of it, in its pure state, will produce immediate insensibility and speedy death. It is heavier than atmospheric air and therefore falls to the bottom of the mine as soon as it is formed from the combustion of the light carbureted hydrogen. It is for this reason that the miner, who has fallen on his face on the floor of the mine to escape the flame of the burning fire damp, rises as soon as that flame has disappeared and hastens, if he is able, to a place of safety. Indeed, it is easier to protect one’s self from the surging fire above than from the invisible and insidious gas below, so quickly does it form, so deadly is it in effect.

One of the most characteristic disasters of recent times, resulting from the explosion of fire damp and the accumulation of after damp, occurred on Monday, August 14, 1871, at the Eagle Shaft, situated about a mile below the town of Pittston, in Luzerne County, Pennsylvania. At nine o’clock on the morning of that day a driver boy by the name of Martin Mangan was passing along an upper gangway, driving a mule with a trip of mine cars. Just above him lay a section of the mine that had been worked out and abandoned, in the old chambers of which a large body of fire damp had been allowed to accumulate. At the hour mentioned there came a sudden and extensive fall of roof in these old workings. The impulse given to the air by this fall drove it out into the working galleries, and with it the inflammable gas. When the fire damp reached the heading and touched the flame of Martin Mangan’s lighted lamp there was a terrific explosion. At the mouth of the shaft timbers were cracked, clouds of dust poured out, and débris from the mine was thrown violently into the outer air. People who were a mile away heard the noise of the explosion and hastened to the scene. Mining experts knew at once what had occurred. As soon as sufficient repairs could be made to the shaft a rescuing party, led by Superintendent Andrew Bryden of the Pennsylvania Coal Company’s mines, descended into the mine and began to search for victims. Those workmen who were on the other side of the shaft from where the explosion took place were rescued and brought out alive. But little progress could be made, however, toward the region of the trouble on account of the after damp which had accumulated. Up to two o’clock on Tuesday morning five dead bodies had been discovered, and during that day twelve more were taken out; all who had worked in that section of the mine. The positions of these bodies showed that the men had fallen where they chanced to be when the explosion occurred. The first wave of after damp that touched them had made them insensible, and death speedily followed. They died from asphyxia.

“Black damp” is pure carbonic acid gas, containing two parts of oxygen to one of carbon. It is the principal constituent of after damp, which may, indeed, contain no other elements in appreciable quantities. The two mixtures are therefore often spoken of as being the same, and the miners apply the term “choke damp” indiscriminately to either.

Black damp is also given off by the coal in the same manner that fire damp is, and frequently the two mixtures are evolved together. Carbonic acid gas is also one of the products of burning coal, of burning oil, and of the respiration of man and beast. It is about one and a half times as heavy as air, and is therefore always found next to the floor of the mine. This gas is not inflammable. Its presence may be detected by the conduct of the flame of the lamp. In an atmosphere containing but a small percentage of it the lamp light will grow dim, and, as the proportion of gas increases, will become more and more feeble until it is finally extinguished. An atmosphere containing from eight to ten per cent. of this gas may be breathed without immediate danger; it will simply occasion dullness of intellect and numbness of body. This condition changes into one of insensibility as the inhalation continues, or as the percentage of gas is increased, and to enter an undiluted body of it means sudden death. It is stated that the workmen in the Creuzot mine, in France, descended the shaft one morning, on their way to work, not knowing that carbonic acid had formed in the mine during the night. Following one after another along the main passage, they had reached a point not far from the foot of the shaft when the leader suddenly entered into a body of black damp and fell, stricken with asphyxia, before he could utter a cry. The man following him fell also. The third, bending over to draw his comrade out of danger, was himself prostrated, and the fourth, by reason of a similar effort, shared the fate of the others. But the fifth, being an experienced master miner, turned quickly in his tracks and obliged those behind him to ascend the shaft. The black damp is thus quick and terrible in its effect. The greatest danger from it, however, exists, not at the working faces, where it is usually swept away in the ventilating current, but in abandoned workings, where it often accumulates unnoticed.

“White damp” is a more dangerous gas than either of the others, but is not so frequently found. It is carbonic oxide, and consists of equal portions of carbon and oxygen. It is a very little lighter than air, and has a tendency to rise. When present in a sufficiently pure state it burns with a blue flame, but ordinarily it is incombustible and produces no effect upon the flame of the lamp. It is tasteless and odorless, and its presence cannot be detected before it has done its dangerous work. To breathe an atmosphere containing a very small percentage of it will speedily produce a fatal result. It acts on the system as a narcotic, and its effect is produced even more quickly than is that of black damp. It is not thought to be given off in appreciable quantities by the coal at the open faces; but it is formed when the carbonic acid passes through any ignited carbonaceous material, or when steam passes over burning coal. It is therefore produced most frequently by smouldering gob fires, by burning wood in the mines, or by a shaft on fire, and may exist as one of the results of an explosion of fire damp or of blasting powder. It is the most to be dreaded of any of the gases which the miner has to encounter. He may possibly avoid the surging flame of the fire damp, he may escape from the falling after damp, and make his way unharmed through bodies of black damp lying thick about his feet, but if he has still to encounter this terrible white damp his good fortune will have been of little avail; death will almost surely seize him.

In connection with this may be mentioned the fact that under certain conditions coal dust may become violently explosive. When it is mixed with air, with or without the presence of fire damp, and is set into sudden and intense vibration by a heavy powder blast, a fall of roof, or other means, it may explode with greater destructive force than even fire damp is capable of. Happily such explosions are not frequent, all the conditions necessary being rarely present at the same time. It is obvious, moreover, that an accident of this kind could occur only in a very dry mine. It is true also that the dust of bituminous coals is much more liable to be explosive than the dust of anthracite. No well authenticated instances of coal dust explosions have been reported from the anthracite regions, while in mining soft coals they have undoubtedly occurred. Two cases of this kind were reported from France, one in 1875 and one in 1877. No longer ago than November 9, 1888, a terrible explosion of coal dust occurred in a bituminous coal mine at Pittsburg, Kansas, by which more than one hundred lives were lost.

In some mines the inflammable and poisonous gases are given off in such abundance by the coal that it is dangerous to remain in them for even an hour after ventilation has been stopped. At such collieries when, on account of accident, or for any reason, the fan stops running, the men are called out immediately, and are not allowed to enter again until a new circulating current has been established. One of the most notable mine disasters of recent years was caused by the quick accumulation of black damp and white damp in a mine, the ventilating system of which had been destroyed and the shaft burned out by fire. This was at Avondale, near Plymouth, in Luzerne County, Pennsylvania, on the 6th of September, 1869. There were three conditions here, the presence and coöperation of which made this calamity possible. First, the mine was ventilated by a furnace at the foot of the shaft; second, the breaker was built over the mouth of the shaft; and, third, the shaft was the only outlet from the mine. The partition of the ventilating flue took fire from the furnace draught. At ten o’clock in the forenoon a young man by the name of Palmer Steele stepped on the carriage with a load of hay to take to the inside stables. Half way down the shaft the hay took fire from the burning buntons. The engineer saw the flames rise from the mouth and let the carriage, with the young man on it, as quickly as possible to the bottom. There were then in the mine one hundred and eight men. Not one of them came out from it alive. In an incredibly short space of time the flames leaped to the top of the breaker, one hundred feet from the ground, and by the middle of the afternoon the great building was a mass of ruins, covering over and blocking up the only entrance to the mine. It was far into the night before the débris had been sufficiently cleared away to permit of descent into the shaft. Then two men, Thomas W. Williams and David Jones, went down to search for the imprisoned miners. They were scarcely beyond the foot of the shaft when they stumbled into a body of white damp and were stricken with death. The fire occurred on Monday. It was not until ten o’clock Tuesday morning that a sufficient ventilating current had been established to make it safe for men to descend. The greatest distance that it was possible to go from the foot of the shaft on Tuesday was seventy-five feet. Beyond that point the danger from suffocation was still imminent. Only three bodies had been thus far found.

Wednesday morning a rescuing party went up the plane at some distance from the foot of the shaft, and at the head of the plane they found a barrier across the gangway. It had been formed by placing a mine car in position and packing the space between it and the walls with clothing and refuse. This barrier was broken down, but there was no one behind it. Later another party was able to go a little farther, and came to a second barrier. Outside of this lay the dead body of John Bowen. He had come out for some purpose from behind the barricade, leaving open an aperture through which to crawl back, but before he could do so he had died from asphyxia. This barrier was broken down, and behind it lay the victims, one hundred and five of them, all dead, suffocated by the foul gases of the mine. The story of their experiences, their struggles, their sufferings, can never be known.

The disaster which occurred at the West Pittston mine on May 27, 1871, was similar in many respects to that at Avondale. In this case also the breaker, built over the shaft, the only opening to the mine, took fire and burned to the ground, closing the avenue of escape to thirty-six men and boys. These prisoners shut themselves into a chamber, building a barricade across the foot of it to keep out the foul gases; but when the rescuing party broke in to them on the following day fourteen of them were found dead and the rest were unconscious. Of those who were brought out alive four died soon after reaching the surface.