Ian Hay, A Safety Match — CHAPTER XVI (1911)
“ The ordinary collier is paid by piecework—so much per ton for all the coal he hews. This coal is carefully weighed on coming to the surface, and to ensure fair play all round the weight is checked by the men's own representative at the pit-head. Now just as all is not gold that glitters, so all that comes to the surface of the earth from the interior of a coal-pit is not necessarily coal. A good deal of it is shale, stone, and the like—technically summarised as "dirt"—and has to be sorted out from the genuine article by a bevy of young ladies retained at some expense for the purpose. ”
