Thanks to all respondents - the customary helpful (and very swift) response from the forum. The consensus is that, in England at least, 'suf' is correct, although in the States 'sow' is preferred. I should have mentioned that the area/mineral in question is West Yorkshire coal. Howard Sprenger's suggestion that the 'u' in 'suf' should be as northern as possible may present me (a native of Hertfordshire) with difficulties. Thanks again to everyone. Having just read Mr Bernard Moore's interesting post (Bridgewater Canal and Mines), I would also be interested in learning of anything that has been published on the subject. Best wishes. David C.