Friday, 16 December 2016

Mapping Mountains – Hill Reclassifications – 200m Twmpau

Y Ceiliog Mawr (SH 594 598) - 200m Twmpau addition

There has been a new addition to the 200m Twmpau (thirty welsh metre prominences and upward) hill list instigated through analysis of LIDAR data by Aled Williams.  The hill is one that Aled first proposed as a prospective P30 Twmpau approximately two years ago and it then waited to be Trimbled, but as it looked a daunting prospect the Trimble surveyor shied away from his duties, and in the meantime as LIDAR data is proving highly accurate I am using the data that Aled has obtained.

The hill is situated in the Glyderau group of hills with its Cardinal Hill being Y Garn (SH 630 595) and is placed in the Region of North Wales (Region A, Sub-Region A1).  The hill is positioned above Llyn Peris which is to its south and the small community of Nant Peris to its south-east and the town of Llanberis to its west.  The hill is a part of the old Dinorwig Slate Quarries, and can be accessed from tracks leading into the hill from the south-east and from the west.

The hill is known locally as Y Ceiliog Mawr which translates into English as the big cockerel.  I am thankful to Eric Jones for the information relating to this name and the history of the hill which comes from the following two passages on the Geograph website:

The Ceiliog Mawr is an igneous intrusion within the Dinorwig Quarries.  Several attempts were made to remove the intrusion but a considerable section of it remains.  "Ceiliog Mawr" means big cockerel.

Buildings associated with the Dinorwig HEP station have been built around the foot of a slightly modified 'cockerel'.  Three attempts were made in the past to 'slaughter the cockerel'.  In 1896 Mr Brinckman, the general manager, decided that the days of the cockerel were numbered.  On the day, the quarrymen were invited to witness what "a real explosion was like".  The cream of the Welsh aristocracy, and dozens of cameramen, were also invited to watch the demise of the cockerel.  The fateful moment came and the button pressed on the battery firer (the only occasion in the history of the quarry for a battery firer to be used).  A huge pall of smoke emerged from the rock.  When it cleared, Y Ceiliog Mawr stood unscathed.  A visit by the Prince and Princess of Wales in May 1902 was an excuse for another go, this time using two tons of explosive, only to leave more egg on the managers' face.  Finally, in 1905, 10 shafts were dug into the outcrop at a cost of £437-12-2 and explosives set at the bottom of each.  Again, only a few loose rocks were dislodged.  Ever since, the Ceiliog Mawr has been an icon of Dinorwig Quarry.

Current Ordnance Survey 1:50,000 and 1:25,000 mapping does not give this hill any ring contours, as is the norm for areas of land that have been quarried.  The hill is of interest (and quite daunting) as it is only now listed as a 200m Twmpau through the quarrying activities of past years, as it has been left as a stone monolith separated from its connecting bwlch by over 37m of vertical height.

Aled’s analysis of LIDAR data gives the hill the following details:

Y Ceiliog Mawr

Summit Height:  220.3m

Summit Grid Reference:  SH 59467 59848

Bwlch Height:  182.8m

Bwlch Grid Reference:  SH 59538 59823

Drop:  37.5m

Therefore, the 220.3m LIDAR data produced for the summit position at SH 59467 59848, and the 182.8m LIDAR data produced for the bwlch position at SH 59538 59823 is sufficient for this hill to be included in the list of 200m Twmpau hills with 37.5m of drop, and therefore Y Ceiliog Mawr is included in the listing of Twmpau which will be updated accordingly.

The full details for the hill are:

Cardinal Hill:  Y Garn

Summit Height:  220.3m (LIDAR data)

Name:  Y Ceiliog Mawr

OS 1:50,000 map:  115

Summit Grid Reference:  SH 59467 59848

Drop:  37.5m (LIDAR data)

My thanks to Aled for supplying the details of his LIDAR analysis of this hill.

Y Ceiliog Mawr - the new 200m Twmpau.  Photo © Aled Williams

To view an old and a relatively recent photograph of Y Ceiliog Mawr {here} {here}

Myrddyn Phillips (December 2016)

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