Mapping Mountains – Significant Name Changes – 30-99m Twmpau

Rhwng Dau Fynydd (SH 351 929) 

There has been a Significant Name Change to a hill that is listed in the 30-99m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Rhwng Dau Fynydd (SH 351 929)

The criteria for the list that this name change applies to are: 

30-99m Twmpau – Welsh hills at or above 30m and below 100m in height that have 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 30-99m Twmpau by Myrddyn Phillips

The hill is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the coast to its north-west, a minor road to its immediate north and the A5025 road to its south south-east, and has the village of Tregele towards the south-east. 

When the original 30-99m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category. 

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed under the point (Pt. c 40m) notation with an estimated c 18m of drop based on an estimated c 40m summit height and an estimated c 22m bwlch height, with both heights based on interpolation of 5m contouring that appear on the Ordnance Survey 1:25,000 Explorer map. 

Extract from the Tithe map

As the summit of this hill comprises bounded land the details for it were examined on the Tithe map.  The term Tithe map is generally given to a map of a Welsh or English parish or township and which was prepared after the 1836 Tithe Commutation Act.  This act allowed tithes to be paid in cash rather than goods.  The Tithe maps gave names of owners and occupiers of land in each parish and importantly for place-name research they also included the name of enclosed land.  This enclosed land is usually based on a field system, however not every field is given a name, but many are and especially so in Wales. 

Extract from the apportionments

The enclosed land where the summit of this hill is situated is given the number 11 on the Tithe map, this can be cross referenced against the apportionments; it is these apportionments that give the name of the owner or occupier of the land as well as the name of the land.  The land where the summit of this hill is situated is named as Rhwng Dau Fynydd in the apportionments, with the details on the Tithe map appearing in the parish of Llanfechell and in the county named as Anglesey. 

Therefore, the name this hill is now listed by in the 30-99m Twmpau is Rhwng Dau Fynydd and this name was derived from the Tithe map. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Rhwng Dau Fynydd

Previously Listed Name:  Pt. c 40m 

OS 1:50,000 map:  114

Summit Height:  42.0m (LIDAR) 

Summit Grid Reference:  SH 35146 92985 (LIDAR) 

Bwlch Height:  22.0m (LIDAR) 

Bwlch Grid Reference:  SH 35426 92899 (LIDAR) 

Drop:  20.0m (LIDAR) 

 

Myrddyn Phillips (May 2021)