Mapping Mountains – Hill Reclassifications – The 500-Metre Tops of England and Wales – Deweys

Mynydd Ceiswyn (SH 772 139) – Dewey deletion

This is one in a series of retrospective Hill Reclassification posts that detail hills whose status has altered in the listing of the Deweys and where I have had direct association with the status change.  These posts will tie in with a forthcoming Change Register giving detail to this list and its alterations since publication in the Mountain tables book.

Mynydd Ceiswyn (SH 772 139)

The 500-Metre Tops of England and Wales are affectionately known after their hill list compiler; Michael Dewey.  This list mixes metric and imperial height in its criteria to bookend up to the 2000ft height band and takes in all hills in England, Isle of Man and Wales that are 500m and above and below 2000ft (609.6m) in height that have 30m minimum drop.

This list formed one of a number of lists that appeared in the Mountain tables book published by Constable in 1995 and at the time of publication comprised 373 hills with 164 in England, 5 in the Isle of Man and 204 in Wales.  The Deweys have undergone extensive revision since first publication with the initial stages forming the basis of this revision given below:

1995    Mountain tables published by Constable with 373 hills listed as Deweys.

April 2000    Strider (LDWA quarterly booklet) publishes contact details for David Purchase and Myrddyn Phillips who have found and list 24 and 14 possible new 500m tops respectively.

It was expanded versions of the above two lists that formed the basis of the next publication:

25^th May 2000    List of Possible 500 Metre Tops by Michael Dewey listing 44 hills.

David Purchase expands his Additional Dewey 500m Hills and Myrddyn Phillips produces lists of English 500m hills to measure and Welsh 500m hills to measure.

These lists formed the basis of the next publication:

29^th June 2000    Possible/Probable 500’s by Michael Dewey listing 77 hills.  Michael adopts following protocol; if one person proposes that a top should qualify as a 500 by personal survey, and is then confirmed by a second person, it should then be promoted to the main list.

April 2002    The 500+ Tops of England and Wales – The ‘New Deweys’ published in the Strider booklet and listing 66 new qualifying hills.

25^th May 2006    Rob Woodall republishes Michael’s main and possible/probable lists on the RHB Yahoo group file database. 

Mountain tables by Michael Dewey

The details for this deletion appear below:

The name the hill is listed by in the Deweys is Mynydd Ceiswyn, and it is adjoined to the Cadair Idris group of hills which are situated in the south-western part of north Wales, and it is positioned with the A470 road to its north and east, the A487 road to its west and the A489 road to its south, and has the town of Dolgellau towards the north-west.

This hill was not included in the original 1995 Constable publication, but was added to the list on the 8^th January 2005 due to hand-help GPS readings taken by Stephen Walker.  Prior to its inclusion Myrddyn Phillips conducted a basic levelling survey of this hill on the 7^th May 2000, resulting in 95ft / 29.0m of drop.     

Extract from the Ordnance Survey 1:25,000 Explorer map

As heights produced by hand-held GPS readings have a relatively large margin of uncertainty applicable to them, this hill was prioritised for a line survey which was conducted by John Barnard, Graham Jackson and Myrddyn Phillips on the 3^rd November 2007, resulting in 27.4m of drop and this hill’s subsequent deletion from the Dewey list.

During the line survey of Mynydd Ceiswyn

At the summit of Mynydd Ceiswyn

The summit of this hill has now been surveyed by GNSS receiver and this was conducted by Alan Dawson on the 22^nd April 2019, using a Leica RX1250, resulting in a 604.9m summit height.

The full details for the hill are:

Name:  Mynydd Ceiswyn

OS 1:50,000 map:  124

OS 1:25,000 map:  23

Summit Height:  604.9m (Leica RX1250)

Summit Grid Reference:  SH 77241 13902 (Leica RX1250)

Bwlch Height:  577.4m (relative to summit height and line surveyed drop)

Bwlch Grid Reference:  SH 77848 14053 (hand-held GPS during line survey)

Drop:  27.4m (level and staff line survey)

Myrddyn Phillips (September 2020)