Rails to Infinity
Journeys in Liminal Space
The Blue Pool, Slate Mine, Corris, Wales
Minerals such as mica and calcium carbonate give slate lakes a distinctive blue hue when a light is shone into them. The warmth of this azure colour is in marked contrast to the grey and black surroundings.
Exposed Mine Entrance, Corris, Wales
In the Corris area slate veins dip to near vertical. The prized Narrow Vein is only about 20 metres thick and this means that the vein has just a tiny surface outcrop. It forced Victorian miners to follow it into the ground, sinking ever deeper pits and creating seemingly 'bottomless' underground caverns. The dip and width of the Narrow Vein is shown clearly in this photograph. The huge hole is the remains of where the slate once was. My fellow explorer is gazing down into a chasm more than 100 metres deep, just out of sight to the bottom right (see video). The ledge once supported a tramway taking slate wagons out of the mine entrance behind the position where the photo was taken from.
Victorian miners had to be fearless of such exposed places. They had none of the safety equipment explorers use today and precious little light to guide them in the darkness.
'The Time Capsule', Ffestiniog, Wales
High on the wet moors that lie between Blaenau Ffestiniog and the village of Cwm Penmachno are a series of early slate quarries and mines. While prospecting for slate started here in the 17th century it didn't really become a serious undertaking until the mid-1800's. The early mines exploited slate which outcropped on or near the surface - tunnelling underground was an expensive business.
The shallow adit (tunnel) in this photograph is typical of this early prospecting. It is barely more than 20 metres below the surface and was originally dug in the hope of hitting a rich slate vein in the 1830's. Today it remains 'fossilised' in time. The daylight at the far end is where a later deep pit has sliced through the adit, which now appears like a window half-way up the pit wall. The other end, behind the camera, has likewise been pierced by the roof of a later underground chamber.
This remote section is now marooned as a time capsule of the early days of mining and to the men who boldly believed that rich slate was to be found here. Oh - and what a place for a very private swim!
Internal Incline, Ffestiniog, Wales
Ffestiniog is at the heart of the Welsh slate industry now recognised as a UNESCO World Heritage Site. The many slate veins found here dip at an average angle of 30 degrees, unlike in Corris. Here Victorian miners followed the veins and constructed inclined planes down to a series of floor levels and up which slate wagons could be winched to the surface.
The photograph is taken from halfway down the main incline of the last of the large slate mines to be worked underground in North Wales, closing in 1999. The incline is remarkable. It once had 4 separate tracks each leading from the different floors along its way. It leads nearly 100 metres from the surface at an angle of 30 degrees following the 'Back Vein'. At the bottom further inclines - some even bigger (see below) lead ever deeper. In total there were 10 floors here, occupying an underground area of about 2,000 metres by 500 metres and reaching a depth of 250 metres.
The archive video below shows the incline in operation shortly before the mine closed.
The Gold Mine that Never Was, Dinas Mawddwy, Wales
During the 1850's 'Gold Rush' fever swept across Wales! Prospectors were desperate to secure investment from wealthy venture capitalists, often at the expense of facts. The 'Red Dragon Gold Mine' - so named to be attractive to English investors - opened in 1852 with grandiose promises of rich gold deposits. 8,000 £1 shares were issued and with this income the mine company commissioned a 'Perkes patent
crushing and amalgamating machine' for £1,050 - £150,000 in today's money! However, it is thought that unscrupulous salesmen lied about the machine's effectiveness. When it eventually arrived at the mine it was found to be the wrong model and another £500 had to be spent fixing and installing it. The machine used huge quantities of expensive mercury to amalgamate gold from the mined ore. However, in January 1856 on its first use, more than 500 kilograms of mercury escaped, killing all the fish in the River Dovey. The mine went immediately out of business, with more than £1,000 of debt. 'More
gold
was put in than got
out'.
The abandoned mine flooded and was forgotten until the mid-1980's when the entrance was rediscovered and it was drained. Today it oozes mineral deposits - though there's no sign of any gold and likely there never was. It is a hazardous place too. The ancient timbers at the far end of the mine having been submerged for 130 years are rotting and combined with sulphurous minerals in the rock, there are toxic sulphuric acid pools and lethal hydrogen sulphide gases. But it is extraordinarily beautiful and has a fascinating story to tell!
The 'Psychedelic Adit', Corris, Wales
An adit is a horizontal passage with the purpose of providing drainage for, access to or transportation from a mine. This adit is some 300 metres long. Slate slabs were lowered from chambers down shafts that dissect the adit at its innermost end onto wagons that took them to the mill close by its mouth. At this point the adit has cut through bands of iron and manganese providing a colourful and mesmerising passage (see video).
The Daylight Hole of the 'Hollow Mountain', Corris, Wales
The Corris Narrow Vein of slate was mentioned in the Exposed Mine Entrance. It was highly prized for its deep blue colour and hardness. However, unlike Ffestiniog slate, it resisted splitting and instead was mainly utilised as slabs for fine billiard tables, windowsills and lintels. It was even enamelled for fireplaces and church pulpits.
Perhaps the most spectacular of all Welsh slate mines is the one affectionately called by explorers the Hollow Mountain. Here a particularly pure section of Narrow Vein has been hewn from the surrounding rock leaving behind a huge void through the mountainside 20 metres wide and 300 metres deep. To support the surrounding rock, arches of slate were left in place. If ever a place resembled 'The Mines of Moria' then this is it! Over centuries brave
men created this beautiful abyss, where light pervades even the deepest recess.
The size of this place is beyond the human scale - comparisons with
cathedrals or double-decker busses fall woefully short. There is simply nowhere like it!
The photograph and video can only go so far as to convey the scale and drama here. This is 'Twll Golau' - 'Daylight Hole'. The deep blue lake at the bottom of the chamber lies some 200 metres below the surface, yet daylight pours down illuminating the underworld. To stand in this chamber is a truely profound experience.
The 'Hollow Mountain', Corris, Mid Wales
The 'Hollow Mountain' has been mined since the 14th century and only ceased production in 2003, making it the longest continually operated slate mine in the world.
The first photo below illustrates the skill by which the miners left delicate rock arches to hold the surrounding mountain in place.
The next two are taken at the bottom of the huge 'Twll Golau' chamber shown above. The rail track, with the 'Indiana Jones'-like wheels, ran right through the mine. It can be seen through the little arch to the right of the spectacular blue lake which now lies at the bottom of the chamber. The remarkable reflection in the lake shows the opening of the chamber to the surface, a full 200 metres above.
The last photo is taken looking up 300 metres to the surface at the deepest point of the mine, under the summit of the mountain it lies beneath.
Originally there were 8 horizontal adits about 20 metres below one another. Chambers of slate were excavated out from the adits and separated by rock pillars. As time went by the top chambers met those below and so on until these enormous voids were created.
PLAY 'HOLLOW MOUNTAIN'
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Ffestiniog Slate, Wales
The following photographs are of the mine mentioned in The Internal Incline. Slate had been exploited here since the early 1800's, but the mine came to prominence when it was purchased by the wealthy entrepreneur Sir William Fothergill-Cooke in 1861. Cooke had made his fortune through his co-invention of the electric telegraph with Charles Wheatstone, which they sold to the Great Western Railway after establishing the 'Electric Telegraph Company'. He was always on lookout for new inventions to make him money and one of his principal reasons for buying this slate mine was to develop a tunnel-boring machine with a Scottish inventor called George Hunter. A worked-out part of the mine was sectioned off behind a wall and there in private, the Cooke-Hunter Tunneller was trialled and modified (more about that below).
Cooke invested heavily in his mine and its mill, so that by the time he died in 1879, it had become very profitable. Indeed, it continued to be developed by making use of the latest technologies. For example, hydro-electric power was utilised from the early 1900's to drive the internal inclines and for lighting.
The first photograph shows another of the internal inclines leading down from the middle floor to the bottom of the mine. The sheer scale of this massive 30-degree passage is breathe-taking and illustrates the bold approach taken here to win slate. The photo is taken from one of several 'landings' to the floors served by the incline. The floor below is clearly visible. Today the bottom of the incline disappears into deep water as the lowest levels of the mine are now permanently flooded.
The second photo is of a beautifully preserved miner's staircase. Look carefully and you will see that this is completely submerged. The stairs tantalisingly lead down into the flooded part of the mine. They probably descend more than 20 metres to the next floor down - but sadly what treasures lie there will now probably never be known.
The large chamber with the 3 explorers is a typical Ffestiniog chamber. Probably carved out by just 2 men over many years it is hard to imagine how many houses it provided roofing slate for! The tiny figure at the top is standing on a huge pile of slate waste. Once a chamber was worked-out, then it made sense to back-fill it with waste rock rather than spend time and money carting it to the surface. Note the massive drystone wall behind the figure. This was built here to stop waste rock from the chamber on the floor above falling and causing a landslide.
Lastly, another miner's stairway. This is very similar to the submerged one above and led the miners up to the surface floor by floor, as inclines weren't safe places for 'pedestrians'. The wonderful craftsmanship that went into making these slate steps is a joy to behold and how the steps have been worn down by generations of miners' feet!
The 'Corris Binoculars', Wales
Sir William Fothergill-Cooke formed a partnership with George Hunter to pioneer a tunnel-boring machine in the early 1860's, as mentioned previously. They tested and refined this in Ffestiniog, but Hunter himself purchased a quarry in Corris, in mid Wales to work on the patent and to provide a demonstration showcase to sell the machine to other mine owners.
The Cooke-Hunter Tunneller, as it was called, was a rail-mounted turbine that turned rotating cutters (see the archive photo below). For the cutting edge, steel bolts were used with sharpened, conical heads. The machine could be adjusted to provide a cutting diameter of between 1.5 and 2.25 metres. The cutting head revolved at 1 to 2 revolutions per minute. It took 3 to 5 hours to cut just 0.6 of a metre. At this point the whole machine had to be withdrawn to allow miners in to clear the loose rock, which could take another 5 hours. This meant that the machine was sitting idle for long periods. Hunter's solution was to develop a double-boring tunneller that would drive a parallel bore next to the one being cleared by miners. In this leap-frogging way, the machine was in constant use and the finished tunnel would be twice as wide.
In 1864 Hunter deployed the new double-tunneller in several parts of his quarry. This explains the origin of the peculiar 'Corris Binoculars' - 30 metre, perfectly rounded tubes each about 2.25 metres in diameter. In the intervening years the land around the 'Binoculars' has been mined away, so they are now left perched on a ledge, with part of the original bore left as a separate outcrop.
My first photograph demonstrates how the 'Binoculars' got their nickname - it is as if you are looking out through a set of field glasses. The 2 distinct bores may be seen here, as well as the remnant of the bore beyond that survived later quarrying.
The second view is looking inside the 30 metres to the end of the bore. Clearly the second bore on the right was never finished, as the majority of what remains is single bore only.
Standing inside the 'Binoculars' is a multi-sensory experience. Light spirals to the innermost depths. Stamp your foot or sing a loud note and the whole tube resonates with a metallic sound - just like a huge temple gong (as in the video below). The sides look like they were cut yesterday and certainly not 159 years ago. It really is the most amazing place.
Sadly for Cooke and Hunter, the tunneller never caught on in the Victorian mining industry - it was simply too slow and cumbersome. However, today's modern tunnelling machines owe much to its pioneering design.
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