"As if it were a quarry, rather than a mine. The seam is worked on successive levels, but, even then, it is impossible to prevent constant accidents from the fall of coal or the sudden collapse of a roof. Take it the world over, and ten miners are killed every day in collieries alone. I told you coal mining was dangerous."
"But are there any of those thick seams in the United States?"
"None of the really thick ones. There's a 40-foot anthracite seam in Pennsylvania. But in France, near the famous Creusot works, there's a bed of coal which is 130 feet thick. It's a basin, though, rather than a seam.
"So you see, Anton, every coal mine is different, with its layers or seams of coal of different thicknesses and at varying distances apart. Some pits are near the surface, some are very deep; some coal is full of gas, other has very little; some coal is so hard that every bit of it has to be blasted, in other mines the coal is so soft that the hewer spends half his time spragging the face so that the coal doesn't fall on him when he's undercutting or holing. Don't you make the mistake of thinking that all a miner has to do is to use his pick! He's got to know his business thoroughly or he's useless to the mine boss and a danger to all his fellow-workmen.
"And that isn't all, Anton, not by a good deal!
"Coal mining might be bad enough, even if the coal seams always ran level. But it's very seldom that they do. They run up-hill and down-hill in all sorts of fashions and play hide-and-go-seek in a way that's fairly bewildering.
"Nearly all coal seams are broken up by faults. The coal suddenly seems to stop, and, when you go to hewing it the pick suddenly hits against a rock wall, right on the level of the seam. In the North Gallery of this very mine, there's a fault like that. You know where the 'snagger' is?"
"Sure," agreed Anton, "you mean where the cars have to be hitched on to a chain?"
"Yes, there! The coal seam jumps upwards fifty feet. That's why the cars, after rolling down nearly a quarter of a mile, by gravity, have to be pulled up fifty feet by an endless chain, to rejoin the same seam and then to go rolling on down by themselves."
"Just what are faults?"