"First of all," he began, "teacher told us that coal can"t be dug up anywhere. The right name for a place where coal can be got is a coalfield. In the ground under the coal-field there is coal.""Yes," said Willie, "but coal, like all other minerals,is always found in beds or layers. These beds are often many hundreds of feet down in the earth.""The mine has to be dug right down into the coal-bed," said Fred. "At first it is only a deep wide pit, going down, down, through all the beds that lie above the coal. This pit is called the shaft.
