Presumably this was a roofing shaft?
🔗Bryneglwys-Slate-Mine-2-User-Album-Image-34382[linkphoto]Bryneglwys-Slate-Mine-2-User-Album-Image-34382[/linkphoto][/link]
It's at the far end of the 20 fathom level (?) in Bryneglwys, so would have (presumably) been among the last parts to be worked: it looks as if this roofing shaft was abandoned in the process of being driven.
The one thing that's confusing me slightly is that it's on the underside of the vein, albeit that the vein runs at perhaps 75% to the horizontal.
In standard Ffestiniog practice, the roofing shaft would have be driven under the overlying hards, yet this seems to have been driven
over the
underlying hards, which would make working rather interesting.
I guess the other option would be that this is the start of a manway or ventilation shaft? - or that I've missed something very obvious!
Hello again darkness, my old friend...