Ballast Island

One of the special features outside the harbour at Porthmadog is a man made island called Cei Ballast. This was formed by pebbles and rubble deposited by sailing ships when they arrived at Porthmadog to pick up slate in the 19th Century. This slate was delivered to destinations all over the world. A sailing ship was prone to capsizing in high winds if it did not have cargo to lower its centre of gravity. Consequently ships would fill their holds with rocks from wherever they had unloaded their slate so that they would be stable for the return journey. If you have an interest in geology you can identify rocks from all over the world on the island.