II. DANGEROUS PRACTICES NOT FORBIDDEN BY THE MINES 12 18 XII. THE USE OF BLASTING POWDER IN FIERY MINES XIV. MORTALITY IN MINES. AN EXPLANATION OF THE SYS- XV. UNDERGROUND FIRES AND COAL CARGOES. THE PRO- INUNDATION OF WORKINGS BY INFLOW OF WATER. XVII. THE BUNKER'S HILL COLLIERY EXPLOSION. BLASTING AND THE DIFFERENT FORMS OF SAFETY ACCIDENTS IN MINES. CHAPTER I. THE USES OF THE BAROMETER AND THERMOMETER IN COAL MINES. EXPLOSIONS and other accidents may be often traced to the fact that the miner, or duly appointed person in the mine, does not pay sufficient attention to the readings of the barometer in the pit. This instrument is as certain a monitor of gas in the mine as it is of storm above ground. The readings given by the barometer and thermometer at the pit bottom, compared with those given by a duplicate set of the above instruments at bank-i.e. at the surface-give those in charge of the pit timely warning that goaves, stopped out gob-fires, old waste workings, and other parts of the seam in which gas is known to exist, are in a dangerous state; this state is owing to the sudden decrease of atmospheric pressure on the area of the surfaces of the workings, and therefore a sudden or gradual evolution of gas may at any time be expected to take place. Many explosions that have occurred in our coal B mines are to be traced to the neglect of such indications. A writer in the Times' some time ago (1875) maintained that the barometer would not indicate the presence of carbonic acid gas, and was therefore an instrument worthless to mining engineers. This statement is erroneous, for supposing we have two barometers previously adjusted to one another, the one placed in atmospheric air, and the other in carbonic acid gas, the barometers being on the same level, then clearly the pressure of the heavier gas will be greater than that of the lighter, the resistance, if any, in the Torricellian vacuum of each instrument being precisely the same. The barometer is thus constituted a balance, and fulfils distinctly its original, and most important, function. In a coal mine the barometer might not indicate the presence of carbonic acid gas, but it does not therefore follow that the instrument is worthless, for it will indicate the probability of the existence of fire-damp. With a safety lamp we are able to localise the gas and test its composition; we merely want to be told that we must do so, and this is precisely what the barometer does. It is from such statements as appeared in the Times,' in the letter of which we are speaking, that misconceptions arise, and young mining engineers commit blunders which frequently result in loss of life or limb. As early as the year 1850, attention was paid to the barometer and its indications, and we find Mr. J. T. Wodehouse substituting for the words, fair, rain, stormy, the following rules, which were to be observed by those in charge of the ventilating furnaces at the bottom of the up-cast shaft, viz., 'fire slow,' 'fire moderate,' 'fire heavy.' The Mines Regulation Act requires that a barometer shall be placed in a conspicuous position near the entrance of all mines in which dangerous gas has been found to exist (General Rules, Mines Regulation Act, sec. 26), but unfortunately it does not recommend or enforce any standard of efficiency of the barometer; it does not require the instrument to be proved up to any standard of accuracy or delicacy; the consequence is that many colliery owners look at the matter from the economical point of view, and supply their pits with barometers purchased from local dealers in optical instruments, which, in comparison with a standard barometer, are found to vary perhaps of an inch at equal pressure. On inquiring the price which the agent of one of the largest coal and iron proprietors of the midland district paid for his barometer, the answer was, 'We get them in the town, and pay about 18s. for them.' It is not possible that any accuracy can be expected in a barometer at the prices when about 8s. would be expended in mercury, 88. in the wooden case and glass tube, leaving a balance of 2s. for labour, adjusting, etc. It will be observed that this estimate is made on the supposition that the thermometer is presented gratis. |