VITAL AIR TO THE MINER.
Tan importance of the coal-trade having been brought promi- nently to notice by the opening of the new Exchange in the pre- sence of Royalty, it may be well, at such a time, to cast a glance at the working collier, with a view to lessen, if not to remove, the dangers that surround him in the pit.
The mineral fuel which constitutes so great a source of our na- tional wealth is not extracted from the earth without a fearful sacrifice of life ; either cut off suddenly, or slowly, but as surely, destroyed by inhaling the poisonous gases of the mines. Scarcely a week passes without fatal explosions, of which little notice is taken beyond the immediate scenes of the calamities ; nor is it till some thirty or forty human beings have been killed at one flash that public attention is aroused ; whilst the thousands who are sent to premature graves by the daily operating effects of the insidious atmospheric poison are altogether unminded. The "safety-lamp," which in its day was hailed as an important boon conferred by science on the miner, has in practice proved a fatal gift. It has enabled the proprietors of mines to obtain coal in work- ings that were too " fiery" to be approached with unprotected flame, and the miner is compelled to breathe an atmosphere which the wire-gauze of his lamp alone prevents from exploding. The risk of accidents is by this means increased in a greater ratio than the protection afforded by the safety-lamp ; which is liable to get out of order by rough usage in the mine, and the men are so careless or ignorant that they often recklessly remove the thin screen between them and death. It is, however, the deleterious effect on the health of the miners by working in a hydrogenous atmo- sphere which most urgently requires attention, that they may be protected from the abuse of the conveniences of the Davy lamp. At inquests on the bodies of men killed by explosions of fire- damp, the inquiry is generally limited to the immediate cause of the accident ; and if safety-lamps have been freely supplied, the proprietors of the mine are exonerated from blame. The fault is usually attributed to one of the sufferers, who, it is surmised, ex- posed a naked flame to the explosive gaseous mixture; whilst the more important question, whether adequate measures had been taken to prevent the accumulation of the gas, is neglected. Experience has shown that safety in working coal-mines is only to be attained by ventilation : no means, therefore, should be left unemployed to render ventilation effective. Our attention has been directed to the subject by a pamphlet on Mr.' Brunton's plan for the ventilation of coal-mines,* which in many respects possesses important advantages compared with the system com- monly adopted. The method at present in use is this. A large fire is kept burning at the bottom of the upcast-shaft of the mine; the rarefaction of the air by beat causes it to rise up the shaft, on the same principle that smoke rises up a chimney ; and the par- tial vacuum is supplied by air rushing down the other shaft, and urged onward by the pressure of the atmosphere through the various passages of the mine. This plan is so simple, so costless, and it occasions so little trouble, that if it produced sufficient ven- tilating force nothing better could be desired. But the expansion by heat, as at present applied, is not adequate to afford a suffi- ciency of fresh air; nor is the principle capable of being readily adapted to the varying 'conditions of the mine atmosphere. Con- sider for a moment what these conditions are, and it will be per- ceived that it is essential the ventilating power at command should be much greater than the ordinary state of the mine requires. A coal-mine contains numerous winding passages leading to the workings where the coal is extracted; and into these passages the carbureted hydrogen gas exudes from crevices in the coal. Some- times the gas issues in a blast from openings called "blowers," but it generally exudes imperceptibly from smaller fissures. Were there no other reservoirs of gas than the passages and empty spaces on a level with them, the mine might be ventilated effectively by the usual means : but when the coal is extracted the roof falls in, and leaves a large cavity at the top, more or less filled by the debris of the rock piled upwards from the floor. The heap thus formed is called the "goaf," and in some coal-mines it is of great extent. In the Haswell colliery; which was examined by Sir Charles Lyell and Mr. Faraday after a disastrous explosion, the goaf ex- tended over an area of thirteen acres. The carbureted hydrogen gas, being much lighter than common air, ascends into the cavity of the goaf; which forms an immense inverted reservoir of fire- damp, ready to be poured into the passages of the mine when ex- panded by diminished pressure of the external atmosphere. If we assume the spaces in and over the goaf in the Haswell colliery to average one yard in height above the roof of the mine, that reservoir would contain 63,000 cubic yards of inflammable air. A fall of only one-tenth of an inch of mercury in the barometer would cause the air to expand one three-hundredth part of its volume, and there would be two hundred cubic yards of fire-damp poured into the mine from this overflow alone, besides the in- creased exudation of gas from the crevices in the coal The ordi- nary means of ventilation are quite inadequate to free the mine from such an influx, which may occur very suddenly and with- * On the Ventilation of Coal-Mines. By William Branton, M. Inst. C.E. out any perceptible notice. The plan proposed by Mr. Brunton, and which has been successfully applied in South Wales, is to produce a current of air by mechanical force. A gigantic blower, similar in principle to those now commonly used instead of bel- lows, is placed at the top of the upcast-shaft, and rotary motion is given to it by a steam-engine. The top of the shaft being closed, the air which supplies the machine is drawn from the mine, and in this manner a current is forced through the various passages and workings. The power of the machine depends of course on the rapidity with which it rotates. With a revolution of sixty times per minute, the rarefaction of the air is equal to 4.3 pounds on the square foot; by doubling the velocity the amount is quadrupled ; and one hundred and fifty revolutions per minute produce a force of 27 pounds. The rarefying effect of a furnace at the bottom of a shaft 900 feet deep is estimated at nine pounds on the square foot. Mr. Brunton's blower possesses such a power of rarefaction, that, he states, " the atmosphere of a colliery during the absence of the workmen may be subjected in half an hour to an artificial exhaustion equal to three, four, or five-tenths of an inch of mercury ; producing in the colliery, during the absence of the workmen and their lights, the very same exudation of the gases that would have taken place during the natural change of the atmosphere indicated by a like fall of the barometrical co- lumn."
With the mechanical plan, a known effect is produced by a known velocity, and the superintendentmay thus adjust the venti- lating power to the state of the mine. This capability of quickly increasing the supply of fresh air constitutes an important feature of the mechanical system. That a more effective mode than the furnace is wanted for ventilating mines, has been fatally proved ; and those of our legislators who take an active interest in im- proving the physical condition of the working classes cannot do better than direct their attention to this subject. Instead of en- forcing the use of the safety-lamp, the thing to be done is to com- pel the proprietors of mines to adopt such a system of ventila- tion as will render safety-lamps unnecessary.