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> Problem: > > Suggested mining trenches from antiquity which have become unmetalled lanes > and cut through the bedding plane in Devonian Slates. Current depth 13m x > 4.6m wide and up to 900m long. Known to have been filled up by 3m in 20th > century. > > Suggestions as to best method of survey to reveal original depth please. > > Regards, > > Trevor. Dig'em by sampling trench...if you can get the authority and the finance... ;-) Ian