September 1908. Gary, West Virginia. "Drivers and Mules in a coal mine where much of the mining and carrying is done by machinery. Open flame on oil headlamps." View full size.

From the Web site of the Pennsylvania Historical and Museum Commission and the Museum of Anthracite Mining in Ashland:

When men first began to tunnel into the earth to remove coal, open flame lamps or candles were the only devices to light one's way. If a miner opened a pocket of lethal gas, the lack of oxygen could not only snuff out his open flame light — a warning too late — but the lives of miners also could be snuffed out. This is why miners often carried caged live canaries into the tunnels. Canaries are more sensitive than humans to diminished oxygen and poisonous gases and provided an early warning to miners. Even more obvious, an open flame could trigger an explosion or fire. One of the significant collections on display at the Museum of Anthracite Mining is a series of safety lamps. After an explosion in England killed ninety-two miners, a society formed to study and prevent mine explosions approached Sir Humphrey Davy (1778-1829) for his help. In 1816, Davy invented a safety lamp with a wick surrounded by cylindrical netting. The Davy lamp was designed so the flame was quickly extinguished in the presence of dangerous gases, giving the miner enough warning to escape. On the other hand, the lamp did not give off much light and could be extinguished by drafts of harmless air.

It was the invention of the battery lamp that revolutionized safe light for miners. Once tungsten replaced carbon filaments, which uses less current, it became possible for portable batteries to be carried by miners. Thomas Edison is lauded for his design in 1913 that provided the miner with a lightweight storage battery, clipped to the trouser belt and connected by a wire to a lamp backed by a parabolic reflector that was fastened to the miner's hat. The wire was locked in place to help prevent a miner from disconnecting it, possibly sparking an explosion.