Did you know ........ There is a naturally-formed cave system extending at least from St. Winefrides Well to Rhosesmor. Halkyn’s Caves The Halkyn area may be noted for its history of lead mining and its landscape, but deep below the surface lies an extensive, naturally-formed cave system extending at least from St. Winefrides Well at Holywell to Rhosesmor, over 5 miles (8 kilometres) to the south. Tantalisingly, only small parts of this cave system have been seen by miners or modern-day explorers, but the parts that have been entered include one of the largest and most interesting natural underground chambers in the UK; Powells Lode Cavern and lake. The smaller caves During the driving of the Milwr Tunnel, blasting at the tunnel face in 1917 broke into a flooded part of the cave system at the intersection of the tunnel with Pant Lode. The resulting flood washed loaded mine cars down the tunnel and brought in thousands of tons of sand from the cave above. The well at Holywell dried up a few hours later. Water levels in mines across the mountain were also affected. The chamber intersected by the tunnel forms a Z shape when viewed from above, and is about 70 feet long, but it becomes too tight at the point where water enters from a narrow passage. As a result of the lowered water table, miners discovered a number of small cave passages and larger natural caverns, most lying deep beneath Halkyn and Rhosesmor. A cross-section of an old mine survey shows one of these caverns in Deep Level Mine under Halkyn village. Another short cave passage was explored close to the Bluebell Inn, Halkyn at a depth below surface of about 500 feet, but this was blocked by glutinous mud after less than 100 metres. A further exploration involved a body-sized tube beneath Tiger Tim’s factory at Rhosesmor. This was explored as far as humanly possible but again, it failed to break into any significant passages. Two larger caverns were found on Great Halkyn Lode about half a mile north-west of Moel-y-gaer some 600 feet below the surface. Each is about 30 yards long and over 40 feet in height. An interesting natural chamber was found in 1910 by miners in the Catch Lode near Pen-y-Bryn Shaft just west of Halkyn village. Mine surveyor J. Humphreys wrote these pencilled notes on his survey of the vein….. “The open part (of the cavern) showed a big rip had been made inside the hill as if one of the natural forces somehow got loose; the cover was torn off the lode as if by an electric shock, descending in zig-zag form as a flash of lightning before thunder. The descent of the burst went along the blade of the lode, from top downwards, on line of underlie………. The rise was damp with sweat, stones drop off the sides and roll down the stope suddenly. When I booked these notes 10th Sept 1910, I saw the rise was not a safe place to obtain angles with a good instrument”. (Source: Flintshire Record Office REF: D/HM/89) Powells Lode Cavern The most notable cave feature discovered to date is Powells Lode Cavern and its ‘bottomless’ lake at sea level under Rhosesmor. First entered in 1931, the cavern was originally found to contain two lakes, one of which was later filled with waste rock by miners. Several attempts were made to measure the depth of the remaining lake, but because the walls below water level veer away from vertical, the plumb-weight lodged at varying depths at each attempt. The deepest recorded depth was 200 feet, of which about 125 feet lies below sea level. Hence it has gained a rather fanciful reputation as being bottomless. Above water level, the cavern is shown on mine plans as rising a further 165 feet, hence the natural cavern has an overall vertical extent of at least 365 feet. A further series of interconnected large chambers runs north from Powell’s Lode Cavern along Barclay’s Lode for a distance of 300 metres, before dipping below sea level. Prior to mining, much of the water percolating from the surface of Halkyn Mountain passed beneath the lake at Powell’s Lode, eventually finding its way to St.Winefride’s Well at Holywell. Today however, the lake overflows into the Milwr Tunnel at the rate of about 4000 gallons per minute, eventually running out of the tunnel entrance at Bagillt. Although cavers have searched the mine workings extensively hoping to discover the main cave system, success has so far eluded them. It is probable that the largest part of the cave system lies well below sea level and may therefore be inaccessible, but another section undoubtedly exists above sea level between the Pant Lode and St. Winefride’s Well. No doubt explorers of the future will continue searching for this elusive and interesting system.
Posted on: Thu, 09 Oct 2014 06:48:21 +0000
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