It can hardly be cause for wonder that the miner should be superstitious. His life is passed in a dark and gloomy region, fathoms below the earth's green surface, surrounded by walls on which dim lamps shed a fitful light. It is not surprising that imagination (and the Welsh imagination is peculiarly vivid) should conjure up the faces and forms of gnomes and coblynau, of phantoms and fairy men. When they hear the mysterious thumping which they know is not produced by any human being, and when in examining the place where the noise was heard they find there are really valuable indications of ore, the sturdiest incredulity must sometimes be shaken. Science points out that the noise may be produced by the action of water upon the loose stones in fissures and pot-holes of the mountain limestone, and does actually suggest the presence of metals.