UKC

I took a walk today up towards Braich Ty Du and Carrnedd Dafydd starting from Ogwen Bank.

At approximately SH 630 654 I noticed what appeared to be the entrance to a tunnel. Going uphill it was just to the left of the path and the entrance was about 3 to 4 feet in height. there was little if any undergrowth and what appeared to be a decent path entering it. Not having a torch I could not see inside. There is no indication of it on the OS map.

Has anyone else seen it or does anyone know anything about it?

Just looked at the GR on the 1:25k map and it's the one I thought it would be as soon as I read your post - down to the left, not long before you reach the gate. Ive always assumed it's either the remains of a trial pit, of which there are loads around those parts, especially in the Moel Faban - Drosgl - Moel Wynion area, or it's a quarry/mine entrance. 

That's it! I always thought trial levels/pits  etc are usually indicated on the OS maps

It’s the entrance to the old Lyles Treacle mine. I once found one of the old tins there a few years back, rusted, but the emblem still visible. 

In that case it must go all the way to Cwm Eigiau. I found one there!

Maybe this was not visible to the mapmakers due to the tree cover? There's nothing at all indicated on the 1:25k map.

I can't remember if there is any spoil or remains of workings on the other side of the path and down the slope in line with the hole.

Ha! We were in Cwm Eigiau today - plenty of industrial history to see there. No treacle tins, though...

They are as elusive as sloes but once you find one!

Have you tried looking at the map on Midsummer's Eve under a Crescent Moon?

Ooh. Does that mean Smaug is going to level Bethesda??

I was talking to a mine explorer about this last week. Has it still got the old stile dumped in it? 

He already has...

Sorry but no - the tin was from a picnic - treacle is pumped up into North Sea oil rigs then to Aberdeen & treacle tankers

Cant say I was aware of any

Is it this mine?

https://www.aditnow.co.uk/Mines/Pen-Isar-Nant-East-Other-Rock-Quarry_10207/

There's also another not far away:

https://www.aditnow.co.uk/Mines/Braichmelyn-Slate-Mine_879/

Hi Mike, it's neither of those: the first is fairly close to the road, the second is on the other side of the hill.

I've just had a walk up there this morning and am fairly certain that it's a trial pit, although I'm not sure what for. Slate is the obvious thought but it could be minerals like those on Gyrn Wigau. It's only about 4m long, fairly level floor and sloping roof, all very similar to the other pits around. 

RRD: there was no sign of a stile but I'd like to think that there was a bit of style whilst I was in there...

I'm surprised it isn't on Adit Now - that's normally quite thorough. There are iron and arsenic mines not far away, but like you say, slate is presumably the most likely.

Surely you mean treacle rigs?

Peripheral, but the treacle chat reminded me of Paul Farley's poem about it...

youtube.com/watch?v=xlUkMinegsg&

Exactly, slip of the tongue

https://geotopoi.wordpress.com/2011/07/24/braich-melyn-south-quarry-sion-y-...

and on Aditnow

https://www.aditnow.co.uk/community/viewtopic.aspx?t=1620