Some of our coal crops out at the surface in places where through the ages wind and weather have worn away the overlying clay, stone, and slate. This can be gathered like wood in the forest without danger. The amount of such coal is commercially unimportant. Some lies only a few feet underground so that it is possible to take it by stripping away the thin overlying material and blast and scoop it out with a steam shovel. There are some stripping mines in the anthracite field and a considerable number in the alluvial plains of the West. But the great bulk of our coal is reached by driving drifts or headings into the veins through the sides of hills or by sinking shafts scores, or hundreds, or thousands of feet down through the earth to where the coal lies. From the mouth of the drift or the foot of the shaft, a tunnel or main heading or gangway is driven on and on into the coal usually for miles, with secondary tunnels giving off the main heading into the pitch-black rooms where the miners work. In the cryptlike terminal rooms, the miner with his buddy undercuts the "face" of the coal with his pick or with an undercutting machine, drills shot-holes into the face, sets his charge of powder and tamps it in, and then shoots the coal down. Sometimes, for the sake of speed, he shoots it down without undercutting, and in the anthracite mines where the coal is too hard for undercutting, direct shooting from the face is the general practice. This blasting of a friable and inflammable substance fills the cellared air with minute particles of highly explosive dust. As the mines go deeper and further away from the opening they accumulate gas and underground water. The greatest number of injuries and deaths in the mines, and coal mining is among the most hazardous of all occupations, result from the falling of overhanging rock and coal; but the catastrophies which have shocked public opinion into a sympathetic attitude toward the commoners of the mines do not come from this steady death toll but have resulted from explosions or fires that have trapped and suffocated or burned their scores and hundreds.