Helen (heleninwales) wrote,

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Rock hunting and a new discovery

One of the people in my husband's evening class is working on a geological town trail. The idea is that it will take people on a nice walk around the town and tell them what type of rock the different buildings are made of. It has turned into a sort of joint project with the whole class getting involved and we'd already had one trip around town to earmark some likely buildings. Last Sunday we took the project another step further by trying to identify where the building stone came from in the surrounding area.

The building style in town is rather distinctive. For one thing, the builders often used huge stones, anything up to 5 or 6 feet long and several feet deep near the base of the walls. The other characteristic -- which is making the project more difficult than we expected! -- is that most of the buildings are built out of a jumble of stones of all different types. One would have thought that a builder would order a load of stone from a local quarry and then build the house with it, but it eventually dawned on us that the building stone had probably not been quarried at all, merely collected from the piles of broken rock that tumble down the hillsides. Shaping of the stones is minimal and they are just cunningly fitted together to make the houses, shops and mills that originally made up the town. Only the newer and more prestigious buildings like the Old Police Station and HSBC Bank are built out of neatly squared blocks of stone that have all come from the same spot.

So really the trail need only consist of one building! The end wall of one of the oldest houses in the town features all the different types of building stone available in the locality. This, however, is not going to make a good walk...

In the end we decided to pick the best examples of each rock type from about 9 buildings located on a short circular walk. Specimen stones located, we then set off to examine local quarries to see if we could link a geological outcrop to each building.

The weather was overcast, clammy and grey, so I haven't taken many pictures. The rain just about held off and we had a pleasant day exploring the surroundings trying to find our building stones "in the wild", but today's photo is not of the building stones, it's of something I never knew was there, though I have walked right by it many many times.

Here are Nikki's dogs Celyn and Fudge posing on the rock, which gives you an idea of its scale and totally nondescript appearance.

From Illustrations for blog posts

Once you remove the dogs and look more closely, you can see that a number holes have been bored into the rock.

From Illustrations for blog posts

What could the holes be for? Is it some kind of test drilling?

No, what we have here is a rock cannon! Basically you put black powder in the hole, ignite it and it goes bang! By setting up a line of black powder held in place with goose fat, you can set the charges off one after the other to make a succession of bangs.

I had heard of these before, but I was only aware of the ones further north around the quarries of Blaenau Ffestiniog. I didn't know we had a local one.

Anyway, the chap who was responsible for the town geological trail is also involved in other local projects, including the restoration of a local well and he said that as part of the celebrations for the completion of the restoration project, they got the local fire brigade to fire the rock cannon. If we were home at the time, we must have heard it and just thought it was ordinary fireworks.
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