The early open-flame lamps not only were sources of danger but their\nfeeble varying intensity caused serious damage to the eyesight of\nminers. This factor is always present in inadequate and improper\nlighting, but its influence is noticeable in coal-mining in the nervous\ndisease affecting the eyes which is known as nystagmus. The symptoms of\nthe disease are inability to see at night and the dazzling effect of\nordinary lamps. Finally objects appear to the sufferer to dance about\nand his vision is generally very much disturbed.<\/p>\n\n\n\n
The Perfect Balance Of Survival And Strategy<\/p><\/div>\n\n\n\n
The oil-lamps used in coal-mining have a luminous intensity equivalent\nto about one to four candles, but owing to the atmospheric conditions in\nthe mines a flame does not burn as brightly as in the fresh air. The\npossibility of explosion due to the open flame was eliminated by\nsurrounding it with a metal gauze. Davy was the inventor of this device\nand his safety lamp introduced about a hundred years ago has been a boon\nto the coal-miner. Various improvements have been devised, but Davy’s\nlamp contained the essentials of a safety device. The flame is\nsurrounded by a cylinder of metal gauze which by forming a much cooler\nboundary prevents the mine-gas from becoming heated locally by the lamp\nflame to a sufficient temperature to ignite and consequently to explode.\nThis device not only keeps the flame from igniting the gas but it also\nserves as an indicator of the amount of gas present, by the variation in\nthe size and appearance of the tip of the flame. However, the gauze\nreduces the luminous output, and as it accumulates soot and dust the\nlight is greatly diminished. One of these lamps is about as luminous as\na candle, initially, but its intensity is often reduced by accumulations\nupon the gauze to only one fifth of the initial value.<\/p>\n\n\n\n\n\n\n\n
The acetylene lamp is the best open-flame light-source available to the\nminer, for several reasons. It is of a higher candle-power than the\nothers and as it is a burning gas, there is not the danger of flying\nsparks as in the case of burning wicks. The greater intensity of\nillumination affords a greater safety to the miner by enabling him to\ndetect loose rock which may be ready to fall upon him. However, this\nlamp may be a source of danger, owing to the fact that it will burn more\nbrilliantly in a vitiated atmosphere than other flame-lamps. Another\ndisadvantage is the possibility of calcium carbide accidentally spilt\ncoming in contact with water and thereby causing the generation of\nacetylene gas. If this is produced in the mine in sufficient quantities\nit is a danger which may not be suspected. If ignited it will explode\nand may also cause severe burns.<\/p>\n\n\n\n
The electric lamp, being an enclosed light-source capable of being\nsubdivided and fed by a small portable battery, early gave promise of\nsolving the problem of a safe mine-lamp of adequate candle-power. Much\ningenuity has been applied to the development of a portable electric\nsafety mine-lamp, and several such lamps are now approved by the Bureau\nof Mines. Two general types are being manufactured, the cap outfit and\nthe hand outfit. They consist essentially of a lamp in a reflector whose\naperture is closed with a sheet or a lens of clear glass. The battery\nmay be of the “dry” or “storage” type and in the case of the cap outfit\nthe battery is carried on the back. The specifications for these lamps\ndemand that a luminous intensity averaging at least 0.4 candle be\nmaintained throughout twelve consecutive hours of operation. At no time\nduring this period shall the output of light fall below 1.25 lumens for\na cap-lamp and below 3 lumens for a hand-lamp. Inasmuch as these are\nequipped with reflectors, the specifications insist that a circle of\nlight at least seven feet in diameter shall be cast on a wall twenty\ninches away. It appears that a portable lamp is an economic necessity in\nthe coal-mines, on account of the expense, inconvenience, and possible\ndangers introduced by distribution systems such as are used in most\nplaces.<\/p>\n\n\n\n
Although the major defects in lighting are due to absence of light in\ndangerous places, to glare, and to other factors of improper lighting,\nthere are many minor details which may contribute to safety. For\nexample, low lamps are useful in making steps in theaters and in other\nplaces, in drawing attention to entrances of elevators, in lighting the\naisles of Pullman cars, under hand-rails on stairways, and in many other\nvital places. A study of accidents indicates that simple expedients are\neffective preventives.<\/p>\n","protected":false},"excerpt":{"rendered":"
The early open-flame lamps not only were sources of danger but their feeble varying intensity caused serious damage to the eyesight of miners. This factor is always present in inadequate and improper lighting, but its influence is noticeable in coal-mining in the nervous disease affecting the eyes which is known as nystagmus. The symptoms of … <\/p>\n