1. The History
Abercwmeiddaw slate quarry is located at Corris Uchaf, five miles north of Machynlleth, in Gwynedd, north-west Wales. It operated for just shy of a century between the years of 1849-1938. While the first workings here were underground, the main slate extraction took place via a large pit to the north of the site, although underground extraction was resumed in the 1920s and 1930s. Connected to the Corris Railway via the Upper Corris Tramway, it carried its products to the Cambrian Railways at Machynlleth for onwards distribution. The quarry is famous for its “binocular tunnels” that were driven into the hillside to reach the Broad Vein.
It was a relatively large quarry and at the commencement of operations in 1849, it employed 80 workers. In 1864, an experimental tunnelling machine was used to bore a binocular tunnel into the wall of the main pit. The tunnelling machine was most likely supplied by John Dickinson Brunton, son of the esteemed engineer William Brunton. The machine was powered by a remote steam engine, with transmission via rope. It cut a circular hole in the rock, leaving a central core which was broken off and extracted to leave a circular tunnel. Two tunnels were driven with a slight overlap, resulting in a twin-bore tunnel resembling a pair of binoculars.
An 1871 report by John Imray describes the quarry as a "well-developed concern", at which stage it was yet to be connected to the Upper Corris Tramway. In 1876, the Liverpool-registered Abercwmeiddaw Slate Quarry Company was formed with William Bright as the manager, who acquired the lease on the quarry. By March of the following year, all of the new equipment was installed with slate being extracted via both open and underground workings. Now connected, via tramway, to the Corris Railway, the slate lowered by incline to the mill. However, this arrangement became increasingly challenging with respect to up-haulage, rubbish disposal and pumping, as the extraction pit deepened. The problem was solved by establishing a locomotive-worked tramway at mill level and boring a tunnel from pit bottom to a point just below the mill. There were two mill buildings at the quarry, which housed a number of Hunter's saws used to make regular cuts in large slate slabs. Invented by James Hunter (son of James William Hunter), the circular saws with their innovative replaceable tips were 13 feet (4m) in diameter and driven from pulley shafts that ran along the length of the mill. The now-demolished larger, original mill stood to the south, above the Afon Deri powered by its 45-feet diameter water-wheel. The second mill which remains today is on the same level, but north of the original incline and used to house a Robey steam engine.
Annotated O/S map of the quarry (c) The Mirror Cracked - Own work, CC BY-SA 4.0,
In 1879 the quarry employed some 130 men and produced 3,231 tons of slate. By 1882, this had risen to 188 men and 4,173 tons. However, despite the company being well capitalised, it struggled to make a profit. A year later output was down to 2,875 tons with employment shrinking to just 80 men. The writing was on the wall and in 1885, the quarry wrote to the manager of the Corris Railway apologising for the late payments of its bills. Then a year later, in February 1886, the quarry closed. Its associated tramways and equipment were then put up for sale in 1893. Having found a new owner, the quarry resumed production in the late-1890s. In 1899 a new steam engine was installed, and records show that 200 men were in the employment of the quarry owners. The reprieve was short-lived, though, and the quarry continued to struggle financially before being wound up again in 1905.
The view over Corris Uchaf, circa 1885, with the very prominent waste slate tips of the quarry on the right hand side of the picture:
The quarry as it appeared on an O/S map in 1900:
Share certificate for five £100 shares in the Abercwmeiddaw Slate Quarry Company, dated 1898:
In 1906, the quarry and its equipment were put up for sale for a second time and sold to Maden McKnee of Liverpool. A new company, again named the Abercwmeiddaw Slate Quarry Company, was formed in 1911, but did no better, and went into liquidation in early 1917. The liquidator tried to sell the quarry as a going concern after the end of the First World War and between 1920 and 1923 it changed hands several times, but was most likely not worked for its slate. Some quarrying did take place in 1924, though, with the production of slabs for cisterns, billiard tables, and electrical switchboards. The nearby Braichgoch slate mine stopped using the Upper Corris Tramway in 1925 and the Corris Railway closed the tramway in 1927, forcing Abercwmeiddaw to send its output to Machynlleth by road via lorry. Sporadic working continued under the management of William Parry, through the late 1920's into the 1930's. In 1935, a new company, the Abercwmeiddaw Slate and Slab Quarries Ltd. was formed and were the last owners to work the quarry, until its final closure in late 1938.
2. The Explore
The Corris area is a great place to poke around Welsh slate quarries and mines. The nearby Gaerwern mine tends to get all the attention due to the abandoned cars that were dumped into one of its shafts, but there are a number of lesser-known sites like the Abercorris slate mine in the immediate area too. Hence Aberswmeiddaw hasn’t had that much attention, with only 2 reports on 28DL previously, namely @The Wombat and his excellent report from HERE back in July 2014 and @Shaun and his equally good and recent report from April 2021 HERE
After parking up, it’s an easy walk up the public footpath which loops back on itself and then follows the path of the former tramway passing, the old incline to the left and the waste piles to right. Eventually, having past the ensemble of buildings, also on the right-hand-side, that was the newer of the two mills, a footpath leads down the hill from the right into the floor of the main quarry pit. Here I had a poke around an old adit before doubling back on myself and then climbing up the scree slope to the famed binocular bore holes. It was a lovely way to spend a couple of hours and recommend this place if you happen to be in the area.
3. The Pictures
First up is the incline down to the Corris railway:
The site of the newer mill is soon reached:
Not sure there’s too much danger here:
This chimney for the mill’s former steam engine is nice:
A quick view across the valley to the workings at Ty’n-y-cuent:
The bore holes in the wall of the quarry soon come into view:
First, though, it’s down to the quarry floor with its small pool:
And, more importantly, this rather nice adit entrance:
A stack of old deads:
Some interesting mineral deposits:
And some old rusting old iron artefacts:
Deeper we go, with the adit quite dry:
The deeper we go, it starts to get wetter:
And with light at the end of the tunnel, wellies (which I don't have with me) required...
So it's time to retrace my steps and go along the left-hand branch that runs parallel to the cliff face:
With its occasion apertures out to the quarry:
However, the adit soon comes to an abrupt end:
Then its back out the adit and on to view the binoculars. After the scramble up, this is what you are rewarded with:
And in we go:
Looking back out. Note the bore continues in the cliff further out, inferring there may have been a large collapse in the quarry wall here:
Looking into the 80m-deep left hand bore hole:
And looking back out:
Finally, looking across to the levels of Gaewern quarry. One for next time....
Abercwmeiddaw slate quarry is located at Corris Uchaf, five miles north of Machynlleth, in Gwynedd, north-west Wales. It operated for just shy of a century between the years of 1849-1938. While the first workings here were underground, the main slate extraction took place via a large pit to the north of the site, although underground extraction was resumed in the 1920s and 1930s. Connected to the Corris Railway via the Upper Corris Tramway, it carried its products to the Cambrian Railways at Machynlleth for onwards distribution. The quarry is famous for its “binocular tunnels” that were driven into the hillside to reach the Broad Vein.
It was a relatively large quarry and at the commencement of operations in 1849, it employed 80 workers. In 1864, an experimental tunnelling machine was used to bore a binocular tunnel into the wall of the main pit. The tunnelling machine was most likely supplied by John Dickinson Brunton, son of the esteemed engineer William Brunton. The machine was powered by a remote steam engine, with transmission via rope. It cut a circular hole in the rock, leaving a central core which was broken off and extracted to leave a circular tunnel. Two tunnels were driven with a slight overlap, resulting in a twin-bore tunnel resembling a pair of binoculars.
An 1871 report by John Imray describes the quarry as a "well-developed concern", at which stage it was yet to be connected to the Upper Corris Tramway. In 1876, the Liverpool-registered Abercwmeiddaw Slate Quarry Company was formed with William Bright as the manager, who acquired the lease on the quarry. By March of the following year, all of the new equipment was installed with slate being extracted via both open and underground workings. Now connected, via tramway, to the Corris Railway, the slate lowered by incline to the mill. However, this arrangement became increasingly challenging with respect to up-haulage, rubbish disposal and pumping, as the extraction pit deepened. The problem was solved by establishing a locomotive-worked tramway at mill level and boring a tunnel from pit bottom to a point just below the mill. There were two mill buildings at the quarry, which housed a number of Hunter's saws used to make regular cuts in large slate slabs. Invented by James Hunter (son of James William Hunter), the circular saws with their innovative replaceable tips were 13 feet (4m) in diameter and driven from pulley shafts that ran along the length of the mill. The now-demolished larger, original mill stood to the south, above the Afon Deri powered by its 45-feet diameter water-wheel. The second mill which remains today is on the same level, but north of the original incline and used to house a Robey steam engine.
Annotated O/S map of the quarry (c) The Mirror Cracked - Own work, CC BY-SA 4.0,
In 1879 the quarry employed some 130 men and produced 3,231 tons of slate. By 1882, this had risen to 188 men and 4,173 tons. However, despite the company being well capitalised, it struggled to make a profit. A year later output was down to 2,875 tons with employment shrinking to just 80 men. The writing was on the wall and in 1885, the quarry wrote to the manager of the Corris Railway apologising for the late payments of its bills. Then a year later, in February 1886, the quarry closed. Its associated tramways and equipment were then put up for sale in 1893. Having found a new owner, the quarry resumed production in the late-1890s. In 1899 a new steam engine was installed, and records show that 200 men were in the employment of the quarry owners. The reprieve was short-lived, though, and the quarry continued to struggle financially before being wound up again in 1905.
The view over Corris Uchaf, circa 1885, with the very prominent waste slate tips of the quarry on the right hand side of the picture:
The quarry as it appeared on an O/S map in 1900:
Share certificate for five £100 shares in the Abercwmeiddaw Slate Quarry Company, dated 1898:
In 1906, the quarry and its equipment were put up for sale for a second time and sold to Maden McKnee of Liverpool. A new company, again named the Abercwmeiddaw Slate Quarry Company, was formed in 1911, but did no better, and went into liquidation in early 1917. The liquidator tried to sell the quarry as a going concern after the end of the First World War and between 1920 and 1923 it changed hands several times, but was most likely not worked for its slate. Some quarrying did take place in 1924, though, with the production of slabs for cisterns, billiard tables, and electrical switchboards. The nearby Braichgoch slate mine stopped using the Upper Corris Tramway in 1925 and the Corris Railway closed the tramway in 1927, forcing Abercwmeiddaw to send its output to Machynlleth by road via lorry. Sporadic working continued under the management of William Parry, through the late 1920's into the 1930's. In 1935, a new company, the Abercwmeiddaw Slate and Slab Quarries Ltd. was formed and were the last owners to work the quarry, until its final closure in late 1938.
2. The Explore
The Corris area is a great place to poke around Welsh slate quarries and mines. The nearby Gaerwern mine tends to get all the attention due to the abandoned cars that were dumped into one of its shafts, but there are a number of lesser-known sites like the Abercorris slate mine in the immediate area too. Hence Aberswmeiddaw hasn’t had that much attention, with only 2 reports on 28DL previously, namely @The Wombat and his excellent report from HERE back in July 2014 and @Shaun and his equally good and recent report from April 2021 HERE
After parking up, it’s an easy walk up the public footpath which loops back on itself and then follows the path of the former tramway passing, the old incline to the left and the waste piles to right. Eventually, having past the ensemble of buildings, also on the right-hand-side, that was the newer of the two mills, a footpath leads down the hill from the right into the floor of the main quarry pit. Here I had a poke around an old adit before doubling back on myself and then climbing up the scree slope to the famed binocular bore holes. It was a lovely way to spend a couple of hours and recommend this place if you happen to be in the area.
3. The Pictures
First up is the incline down to the Corris railway:
The site of the newer mill is soon reached:
Not sure there’s too much danger here:
This chimney for the mill’s former steam engine is nice:
A quick view across the valley to the workings at Ty’n-y-cuent:
The bore holes in the wall of the quarry soon come into view:
First, though, it’s down to the quarry floor with its small pool:
And, more importantly, this rather nice adit entrance:
A stack of old deads:
Some interesting mineral deposits:
And some old rusting old iron artefacts:
Deeper we go, with the adit quite dry:
The deeper we go, it starts to get wetter:
And with light at the end of the tunnel, wellies (which I don't have with me) required...
So it's time to retrace my steps and go along the left-hand branch that runs parallel to the cliff face:
With its occasion apertures out to the quarry:
However, the adit soon comes to an abrupt end:
Then its back out the adit and on to view the binoculars. After the scramble up, this is what you are rewarded with:
And in we go:
Looking back out. Note the bore continues in the cliff further out, inferring there may have been a large collapse in the quarry wall here:
Looking into the 80m-deep left hand bore hole:
And looking back out:
Finally, looking across to the levels of Gaewern quarry. One for next time....
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