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rent of fresh air, as should be done, but in furnishing just such an amount of air as will prevent the miner's lamp from dying out. This gas is the heaviest of all mine gases; it is universally found in the lowest levels of a mine, and requires a strong current of air to remove it. It is invisible, incombustible and non-explosive, unfit for respiration, and a positive poison. It is dangerous to breathe an atmosphere containing eight per cent of this gas, and lights will cease to burn when ten per cent of it is present, and smaller percentages are injurious in proportion. It is found in large quantities in all mines and every man and, boy working in a mine is familiar with it, because of its effect on the light.
Carbonic Oxide Gas, called White Damp.—This gas is the product and the result of combustion of coal and wood, and from powder explusions. It is never met with in mines, from natural causes. It is itself an inflammable gas, but does not support the combustion of other bodies. In mines where powder is largely employed to loosen the coal, miners often suffer from the effects of white damp. After a shot is fired, the miner can neither work nor live in the smoke from a blast, and is compelled to retreat until the same is diffused through the air; and when ventilation is poor, the smoke frequently hangs all day long in the mine in blinding and suffocating volumes. This gas has a more deleterious effect upon the miner than black damp, but unlike it in its non-support of a flame or light, as the miner's lamp will burn with great clearness, in an atmosphere made most deadly by the presence of white damp. It is the most dangerous of all mine gases to those who have had no experience with it. Three per cent of this gas mixed with the atmosphere of a mine will cause death, and in the event of its odor being detected by one experienced, a retreat to fresh air is instantaneous. One volume of this gas to seven of air, when ignited, will become a mass of flame, but the explosive force is weak except where large quantities are ignited, then the force of the explosive is terrific. This gas played a very prominent part in the explosions at the Rich Hill mines, and was doubtless a large factor in the destruction of life and property.
After-damp.-After-damp is the resultant mixture left after an explosion of fire-damp and air. No greater catastrophe can happen a mine than the explosion of a large amount of fire-damp. The burning air of such explosion rolls along the entries of a mine, scorching every living creature within its reach, and such portions of the mine as are beyond the reach of the flame are yet subject to the serious effects of the tremendous force of the explosion, which dashes the miner against
the sides of the mine, blows the stoppings out, breaking doors into fragments, and, in many cases, the cages in the shaft and the pulleywheels above are blown high in the surface air. Then follows the afterdamp, the product of the explosion, which travels the mine on a work of death to all beings exposed to it. It is a most poisonous gas, and very destructive to life; it is lighter than common air, and finds its way to the roof of a mine; is composed of 7} volumes of free nitrogen and one volume of carbon—in all 84 parts. In other words, after-damp is practically the air with the oxygen burnt out by the explosion.
VENTILATION OF MINES.
The ventilation of underground work remains one of the most important subjects claiming the attention of the mine manager. Upon the question of a suitable amount of air and the regulation and distribution of the ventilating currents, depend not only the successful prosecution of the excavations of a mine, but also the health and lives of those employed therein. The appalling accidents so frequently occurring from explosions of fire-damp and other causes, demonstrate the necessity for providing adequate and suitable provisions for the thorough ventilation of the mines, their working-places, road and passage-ways, and the necessity for which has been frequently forced upon the attention of those in charge of mines by legislative enactments.
The atmosphere of a mine, especially that of a coal mine, is liable to vitiation from numerous and uncertain causes, and it is subject to conditions of renewal altogether different from those prevailing on the surface. It is, therefore, of the first importance, and the duty of every mine manager, to give the closest attention to the condition of his mine, and see to it, personally, that the ventilative current is being properly circulated around the entire workings, direct from the downcast or intake. Pure air is found only at the surface, and then only in places which are removed from sources of contamination, such as the hill-tops and high lands; in other localities a vitiation always exists to a greater or less extent, but when we descend into a mine, not only do we encounter the conditions existing as referred to in certain surface localities, where the polluting agents are most abundant and active, but the same conditions are greatly intensified. Hence it is that we often find the atmosphere of a mine laden with impurities and otherwise vitiated to a degree hardly fit to breathe.
We are sorry to admit that the ventilation in some of the mines of this State does not attain at all times to the standard required by the law, and there are various reasons for the defections existing. At some mines we find mine bosses wanting in the knowledge necessary to
provide for, regulate and properly distribute the ventilating current in and around the mine, and we often find them fully as careless in the performance of their duty as they are lacking in the proper experience; they seldom go into a mine, and, therefore, can have no knowledge or conception of its actual condition and requirements, and the injury being inflicted upon the miner.
With the above in view, and the knowledge of the fearful possibilities of incompetent mine management, I feel that I owe it to the miners of this State to most earnestly recommend the enactment of a law requiring all mine superintendents and bosses to pass an examination and secure a certificate of competency, before being allowed to take charge and supervision of mines where 10 or more men are employed.
The shallow coal or coal seams lying near the surface throughout the State being nearly worked out, operators will be compelled in the future to go deeper for the coal, and as more gas is encountered in deep mines than in those near the surface, the skill of the more practical mine superintendent will be demanded, and this we trust will do away with many of the so-called inine bosses of the present day. Defects in the ventilative current were discovered in several of the mines, wbich was due to lack of forethought in the construction of airways, in not making them large enough to admit the passage of a sufficient quantity of air, and want of attention in keeping the same clean at all times.
In the above cases the judgment and knowledge of the mine bosses were at fault, for all bosses should know that the greatest obstacle encountered in mine ventilation is that of small and contracted airways. Defects in the distribution of the necessary quantity of air in many of the mines may be traced direct to leakage through stoppings and break-throughs, and when such is the case the responsibility lies with the man in charge, who is either lazy or unfit in most
There are instances in this State where the mine bosses, although possessing the required energy and qualifications (yet being subject to a superior officer, who has acquired no mining experience, either practical or theoretical), and to hold their places become passive, allowing the judgment of the superior, who is influenced by selfish and economical motives, to override their better judgment. How- . ever, in several of the larger mines, much enterprise is displayed in the matter of improving the sanitary conditions, and in the additional security afforded the miners in other respects. It is only a short time since that, the mines in the vicinity of Rich Hill were considered dangerous magazines of explosive mixtures, and unfortunately sever.
violent explosions at these mines occurred, causing great loss of life and property. By giving more attention to the important matter of ventilation, these mines are now perfectly safe, with sweeping currents of air flowing through them, and a practical miner in charge of each. All of the new mines which have opened up during the past year have adopted the much-improved method of ventilation : that of splitting the air-currents into separate divisions; and really this is the only practical method for the ventilation of extensive mines, and we are very glad to see this fact impressing itself upon the minds of mine owners. No part of the capital invested in coal mines yields better returns than that judiciously expended in securing proper ventilation.
Natural Ventilation.-A natural circulation of air through a mine is caused when there are two shafts or openings of anequal depth. The direction taken by the air.current is influenced by the difference of density in the two openings. In winter the current will be found to go down the shallow shaft and travel toward and then ap the deeper one, but if the weather be very hot the conditions are reversed and the air.current goes down the deep shaft and up the shallow one. It is during the cold weather only that natural ventilation can be relied upon to be of any practical use in a coal mine.
But very few mines in this State are operated on this system of ventilation, and these are local mines, so termed because they operate only in the fall and winter for the supply of trade in the immediate vicinity.
Furnace Ventilation.—The action of the ventilating furnace is to strengthen the natural current by imparting an additional heat to the upcast column, thus reducing its density and lessening its weight, and by reason of which it rushes up the air-shaft, giving way to the heavier air, which in turn becomes heated in passing over the furnace. In this way a continuous current of cold air is made to descend one shaft and constantly force the warm air up the other. The furnace has long been the favorite ventilating appliance at coal mines, by reason of its simplicity and reliability. It is most effective in deep mines, as its power depends upon the amount of air to which its heat can be communicated, and the longer the column of heated air in the shaft in that proportion is the velocity of the ventilating current increased, as these conditions cause an additional length to the hot-air column, conse. quently a brisker ventilation is obtained. A wide furnace will do better service than a bigh one of same sectional area, as it admits of a thin fire over a larger surface, and the more effectually heats a larger amount of air, as it is thus made to pass over it.
Fan Ventilation.-Fans have long been considered as affording the best method so far discovered, in producing a ventilative current in all kinds of mines; they are found to be far superior to the furnace as a ventilative power, and are now in very general use throughout the State.
In the ventilation of a mine, the action of the fan has the effect of reducing the weight of atmospheric air in the upcast-thus causing the air in the mine to expand by the consequent diminution of its weight in the space occupied. The difference between ventilation with a fan and that of a furnace, is in the method by which the equilibrium of the air in a mine is disturbed; the furnace causes the disturbance by expansion from heat, while the fan causes it from expansion by displacement. The efficiency of a fan depends largely upon its construction and the general surroundings.
There are several fans in use at the larger mines that are doing very effective work, while at other mines not one-fourth of the fanpower expended reaches its destination, owing to leakage through defective doors and stoppings. Still another fruitful cause of waste may be found at mines where the fan is located on top of hoistingshafts, exhausting or forcing (as the case may be) through an air chamber, partitioned off from one end of main shaft, and in the effort to force the air current required through an area much too small for its accommodation, the flow of air is not only greatly retarded, but as the partitions are generally fall of holes, much of the air is forced to the surface and lost, never reaching the bottom. Mine bosses are largely responsible for this, as many of them imagine that if a mine is furnished with a good fan good ventilation is assured, regardless of the surrounding conditions; when, at the same time, if they should take the trouble to investigate and find out the amount of air circulating at the face of the workings, not 25 per cent of the work done by the fan could be detected at the face.
It requires more than a well-constructed and effective fan to secure good ventilation; for without the co-operation of a practical mine manager (though the fan may liberally perform its part), who will see that doors are properly placed, hung and attended to, the airways kept large and clean, and the speed of the fan regulated in accordance with the demands of a mine, the miners cannot hope for a healthy atmosphere to work in.
Doors in Mines.-Much can be said concerning the importance of having well-constructed doors placed in mines ; for even though the mine is equipped with a powerful fan or furnace for the supply of air, and it has large, clean airways, with a sweeping current of air com.