While most mines are now lighted entirely by
electric safety lamps, the Davy lamp is still used to test for the
presence of fire-damp. Though flames cannot pass through the wire
gauze, gas can pass in. If fire-damp is present, the color of the
flame in the Davy lamp changes to blue. That change in color says,
"Take care! Danger!"
There is a railroad in this underground city. A car stands near. Our guide tells us to get in. After a ride of about a mile, we come to a room where miners are at work. There are not using hand picks and shovels, as all miners once did. In a great modern mine like this one machines run by electricity do almost everything. The miners merely guide the machines.
An undercutting machine is cutting a long, deep gash in the wall of coal just above the floor. Farther on is a miner drilling holes with an electric drill in a wall of coal already undercut.