Unintended Consequences

There is a Dire Straits song, 'Telegraph Road' (full lyrics), that traces the arc of a (US) road from its chance frontier origins to modern urban dystopia, decline and decay. I like its clever word-play and interweaving of the story of the road with the path of a romantic relationship. Some of the lines rang around my head as we looked on this scene

Then came the trains and the trucks with their loads
And the dirty old track was the telegraph road

Then came the mines, then came the ore

Telegraph road got so deep and so wide

all of these signs saying, "Sorry, but we're closed"

It's not a perfect match, but there are some resonances here. Definitely no urban nightmare, but possibly the closest the Pembrokeshire coast path gets to a honeypot destination - easily accessible and Instagram-ready

In the early 19th century, someone began taking slate from the hillside here and shipping it out in small quantities from the tiny bay below (out of shot). Business was good; they decided to increase production by quarrying down (25m, eventually) into the hill, investing in a steam engine (placed on the flat surface you see on the far side of the pool) to lift out the product. In 1851 they opened a (horse-drawn) tramway to take the slate 3.6km to the next bay, where there was already a harbour for bigger boats and larger cargoes

Possibly by the 1890s, and certainly before WWI, the whole thing was over. Some of the workmen's cottages remained occupied until a severe storm and flood in 1938; now there is no-one here. I have not discovered at what point someone decided to breach the land between the quarry and the sea - apparently in the hope of creating a new harbour. For whatever reason, they did not succeed in doing more than flooding the quarry

The water leaches copper oxide out of the rocks, which gives it a blue-green colour. I have not read this, but I think the copper oxide (which is red-brown) is reacting with carbon dioxide to create copper carbonate - the process that causes copper-roofed churches in Europe to become coated with verdigris

So the outcome is a picturesque pool with an unusual colour that has become well-known as the 'blue lagoon'. I'm convinced the name accounts in part for the press of visitors it suffers from in the summer. If it was called 'the verdigris pit', I think it would be quieter

We were conducted here in the delightful company and deep local knowledge of blippers ceridwen and ppatrick (and four-legged friend), to whom many thanks for a fun and fascinating day