Davey found that burning gases cool when they traveled through a fine wire netting and that if the air was still, the flame from a lamp wouldn't spread. Using those discoveries, in 1816 Davey fabricated his first safety lamp. That lamp utilized a wick surrounded by cylindrical netting eight inches high and two inches around. However, the lamp did not provide much light, and it was not safe if there were drafts in the mine.
Over the years, others changed Davey's early lamp. One "improved" model, which produced a brighter light, substituted gasoline for oil. However, many engineers considered that model more dangerous because the gasoline lamps tended to get hotter, especially where the air was gassy, and its glass cylinders broke more frequently than those on oil lamps. To offset the problems, designers increased both the size of the lamp and its weight. They also substituted thinner glass in the cylinders because thinner glass was less likely to break from uneven expansion than the heavier glass; however, the thinner glass broke more often when a miner dropped his lamp and could trigger an explosion. Another danger of the gasoline model was that the flame went out more frequently, thus requiring a miner to relight it -- again risking an explosion.
Over the years other inventors worked on different versions of the safety lamp, and while those improved lamps did lessen the danger of explosions, they did not eliminate them. In 1906, nearly 53 percent of mine explosions were still caused by miners' lamps, and in 1912, the U.S. Bureau of Mines reported that at least two disasters had been caused by safety lamps.
The electric lamp was still in the experimental stage in the early 1900s. Inventors had not been able to develop a successful portable electric mine lamp until tungsten lamps replaced carbon filament lamps. Because tungsten lamps used less current, the batteries were small and light enough that miners could carry them and still move about freely.
In addition, inventors needed to address a host of other problems. Could lamps be made so they would not ignite mine gasses? Could they produce enough steady and uninterrupted light for at least one shift? Would they burn in any position? Were they light in weight, simple to operate, and durable? Was the battery easy to charge and inspect? It was a real challenge to develop a suitable electric lamp.
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