The miners, we notice, wear little electric lights on their odd helmet-shaped hats. When we reach the bottom of the shaft, we see lines of electric lights stretching away into the darkness.
Our guide tells us that electric lights are the only kind allowed in this or any other modern mine. Why? There are dangerous gases, or "damps," in the coal. "Choke-damp" smothers, "white-damp" poisons, and "fire-damp" explodes at the touch of a flame or a spark. In this mine a ventilating system sweeps the dangerous gases out and draws fresh air in. Yet it will not do to take the chance that any open flame might happen to meet fire-damp somewhere.
Long ago, before electric lights were invented, miners had to work by the open flames of candles or lamps. Every now and then many miners were killed by terrible explosions.
Then the great English scientist, Sir Humphrey Davy, found that flame will not pass through a fine wire screen of gauze. He then made one of the world's great life-saving inventions; he invented the famous Davy safety lamp. No one know how many miners' lives that lamp has saved.