Preston Moor Colliery was presumably being worked by systematically by
sinking numbers of shafts till at least 1711 (quote below) which must have meant a
complicated method for robbing the pillars or at least retaining support for
the shafts.
"I mention not the Sump Coals gott at the soaling of every fresh Pitt which
may be ten or twelve corfes at a time which were not accounted for"
The sump coal was taken without paying any duty to the Duke of Bolton.
Regards
Ian Spensley
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