Rock Cannon, Mynydd Llandegai

Rock cannon, looking east towards Penrhyn Quarry and the Carneddau


12 February 2011

Gefnan, Mynydd Llandegai

SH 61096 65123; 53.16504°N, 4.07924°W

Further Information

A rock cannon was a traditional pyrotechnic device fired to mark special occasions and celebrations.

It comprised a boulder into which a number of holes had been drilled. Each hole was normally around an inch across by five or six deep, and was linked to a neighbouring one via a shallow channel cut into the surface of the rock. Before firing, the holes were filled with black powder and packed with crushed rock. A black powder-filled goose quill served as a fuse and more black powder was laid in the grooves between the holes. The sights and sounds of a cannon in operation are said to have been rather marvellous.

There are over 200 known rock cannon sites in the slate quarrying areas of Gwynedd.

Rock Cannon (Wikipedia); Rock Cannon at Rhiwbach (Iain Robinson / Flickr)

Rock cannon, looking north west towards the Menai Strait and Anglesey

The larger of the two drilled boulders

Holes and channels

One of the now water-filled holes

Detail of hole and groove

Hole and groove detail, looking west towards Moel y Ci

3 thoughts on “Rock Cannon, Mynydd Llandegai

  1. Great detail on these! Obviously cut in a different way to the ones in Blaenau Ffestiniog, as the linking grooves are straight rather than in the “flowery” pattern. Super photos. I noticed this week that Browsers in Porthmadog had a copy of Griff Rees-Jones’s “Rock Cannons of Gwynedd”.


  2. Pingback: Rock Cannon, Beudy Uchaf, Beddgelert « GeoTopoi

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