1) When there was water in a coal-mine it presented colliers with problems that could only be solved by draining, that is by ‘opening’ soughs or Watergates.
1640 did stope the soowe … so that no man can get coles … til itt be opened and the way to open itt is to Sinke a pitt within three yeards of it, Sharlston
1653 he would join with him in opening a sowe upon Baildon Moor
1774 sow opnin 2 men 2 days, Tong. Alternatively a pit that had been sunk and was being worked was said to be ‘open’: 1597 the myne or mynes of Coales opeind and not opnyd, Beeston
1699 all that my … coalmine … open and not open, Goldthorpe. This last item demonstrates how late a ‘coal-mine’ might consist of more than one coal-pit.