Some years ago, during a systematic investigation of the lungs of miners from all the major British coalfields, it was found that lung dust from Scotland did not fit in with the expected pattern, which was that the dust in the lungs would consist largely of the appropriate seam coal and associated minerals. Further study showed that nearly all the Scottish lung dusts had properties similar to those of soot. It was concluded that most of the pneumoconiosis found in Scottish coalminers could have been caused by soot from naked-light illumination, i.e. open lamps or candles, and that with the changeover to electric lighting, one possible cause of pneumoconiosis has been eliminated from the pits.