A bluecap is a brownie or spirit who worked in the mines of Northern England as a putter, a man or boy employed to push wagons out of the mines. They were usually unseen, appearing only as a blue light; miners would sometimes see the flickering light settle on a full tub of coal, transporting it as though “impelled by the sturdiest sinews”. If treated with respect, bluecaps might even lead miners to rich deposits of minerals.
The blucaps were said to be hard workers, but unlike other brownies they expected to be paid a working-man’s wage. Their payment was left in a solitary corner of the mine, and they would accept no more or less than they were owed, the same as any other putter.