DOUBLE TROUBLE
One of N. Wales’ stranger sights is the result of an entrepreneur’s bizarre binocular vision that left him with just £17 to his name when he died
CENTURIES of slate quarrying have left some extraordinary features across the Welsh landscape.
Among the strangest of them all are twin tunnels shaped like binoculars dug by some of the world’s first boring machines.
Their existence in Gwynedd’s vast slate mines is a story of both Victorian ingenuity and heroic failure.
The steam-powered machines were unable to match the efficiency of low-paid miners equipped only with jumper sticks, hammers and gunpowder.
In the mid 1860s, the machines were trialled at three mines.
One was used to cut an opening to the Cookes level at Maenofferen, Blaenau Ffestiniog, while the most celebrated is at Abercwmeiddaw, near Corris.
Here, bizarre twin tunnels reach around 30 metres into the rock.
Cut in 1864, they resemble a giant pair of field glasses.
One recent visitor was Nic Parry from Shrewsbury, who said: “This was one of those places where you get there and think ‘wow!’ It’s as if those patterned lines were drawn on. It was really quite mesmerising!
“Nature has started to reclaim them, which adds to the beauty of the place.”
The first tunnelling machine was designed by Scottish engineer George Hunter, whose father James had developed industrial stone planing machines in Arbroath.
Their industrial cutters were widely adopted by the slate industry.
One was ordered by the Braich Ddu quarry near Trawsfynyddin 1863.
Boasting four discs, each 4ft in diameter, it was described as “the largest machine of the kind yet made”.
As the so-called “Hunter saw” was manufactured in Arbroath, the only way of getting it to the quarry was by sea, then by boat up the River Dwyryd, followed by a four-mile road journey and, finally, transport along a two-mile length of narrow gauge.
To oversee its installation, George Hunter and his family left Arbroath for Maentwrog in the Vale of Ffestiniog.
Here, he came to the notice of Sir William Fothergill Cooke, joint inventor of the electric telegraph, who used his new fortune to buy a house in Portmeirion.
As Sir William had invested heavily in Maenofferen quarry, and at Hafod Las quarry,
Betws y Coed, he was keen to see if new technology could boost their profits.
George had just patented a prototype tunnelling machine which, in trials in Arbroath, had cut a 5indeep ring in a stone wall in less than five minutes.
Sir William promptly provided the finance for its construction and shipping.
Essentially, the tunneller was a railmounted turbine. For the cutting edge, steel bolts with sharpened, conical heads were used.
The machine could be adjusted for a cutting diameter of between 5ft 6in and 6ft 6in. The cutting head revolved slowly, at one to two revolutions per minute.
Once moved into place, it was clamped in position. Typically, the machine would take about three to five hours to cut a 2ft deep groove into the rock.
The cutting head was then withdrawn from the newly cut groove, and the machine roped back to let miners through. They could then start hacking out the core at the head of the tunnel – a process that could take several hours.
Only then could the machine be pushed back into the tunnel, clamped back in place and the next core cut.
The first tunnel cut this way was probably at Maenofferen, where a 30ft-long single bore can be seen. But it was a laborious operation. The key weakness was the inability to extract the core without the machine being withdrawn. Over the next few years, modified Cooke & Hunter borers were patented, but the central problem remained.
Sir William admitted as much: in one patent, he described how the machine was “idle for nine hours out of every 12”.
His radical solution was to drive multiple tunnels in parallel. After cutting one bore, the machine would be moved to an adjacent rockface, and a second intersecting bore cut.
Once done, it was moved to a third adjacent rockface before returning to the first: the idea being it could be in constant use. For this, a cradle was needed to move the machine between each parallel tunnel. The process was tried with some obstinancy at Abercwmeiddaw, creating its telltale binoculars tunnel.
At Maenofferen, a bizarre “quadruple bore” tunnel was cut in 1868, forever known as “Cooke’s Level”.
Unlike the Cooke & Hunter stone cutting and dressing machines, which were adopted widely in the slate mines of northwest
Wales, the tunnelling machines failed to justify their investment.
Finances were never Sir William’s strong point, as JG Isherwood noted in a paper presented to the National Association of Mining History Organisations conference at Bangor University in 2014.
He wrote: “Cooke may have had some good ideas, but was perhaps lacking in business acumen.
“In late 1867-early 1868, his enthusiasm led to an investment in the Llanberis Slate Company Ltd which was to cost him dear.
“The company was already somewhat dubious, and had expended a large amount of shareholder’s money to little profit by developing the Gallt y Llan slate quarry, near the end of Llyn Peris.”
By November 1868 the company had failed and Sir William was left severely depleted. Within a couple of years he would lose what little he had left.
In 1870, he founded another stone-cutting company in London, shortly after withdrawing from leading roles in the Maenofferen and Bettws companies.
Despite raising £40,000 in funding, the new company would fold within four years. By 1879, Sir William was dead, leaving an estate worth a mere £17.
In a final effort to perfect his tunneller, George filed a patent in 1882 for a machine driven by compressed air. But the world had caught up and overtaken him.
In 1880, work began on the first attempt to dig a tunnel under the English Channel.
This used a superior rotary boring machine capable of cutting nearly half a mile a month.
Despite the two bores reaching 2,110 yards, the project was plagued by fears of a subterranean invasion by the French. After a number of injunctions, it was finally abandoned in 1898.
The Cooke & Hunter machines became footnotes in the history of tunnelling.