page_title: Croesor quarry
section_title: Current conditions
hierarchical_section_title: Croesor quarry / Current conditions
caption_attribution_description: Underground Bridge in Croesor Quarry slate mine en route to Rhosydd Quarry
context_page_description: Croesor quarry is a large underground slate mine in North Wales which was served by Croesor Tramway. Small scale quarrying began in the 1846, and by 1861, there were two companies in operation. They amalgamated in 1865, a year after the quarry was connected to the newly opened Croesor Tramway. Much money was invested in development work, but volumes of useful slate produced were small, amounting to just 226 tons in 1868. Access to the underground workings was by a single adit, and the surface mill was powered by two water wheels. A change of ownership in 1875 did little to improve the profitability of the quarry, and it closed in 1878 or 1882.
  In 1895, the quarry reopened under the direction of Moses Kellow, a fearless innovator who set about modernising working practices and methods. The two-man teams working in the mill were no longer tied to a two-man team working underground, which enabled the mill to operate more efficiently. Following trials with air drills, he decided instead to electrify the mill, building a large hydro-electric station, which generated three-phase alternating current, rather than the direct current recommended by British manufacturers.
context_section_description: Croesor is connected to the nearby Rhosydd quarry by a tunnel that was built to aid surveying and settle boundary disputes. Apart from Chamber 1 East, a huge chamber in which the roof has collapsed, most of the accessible mine is in reasonable condition. Below the adit level, the mine is flooded and inaccessible. In spite of a series of collapses, particularly in the Rhosydd quarry, an underground journey from Croesor to Rhosydd is still possible and is considered to be a classic trip for mine explorers. It is known as the Croesor–Rhosydd Through Trip. Fixed ropes, home-made suspension bridges, zip wires, and inflatable boats have been installed which make it possible to complete the journey in comfort although not necessarily in safety.
caption: Final and most awkward crossing in the Croesor to Rhosydd through trip
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