Old canal remain in field opposite Glais Mill Taf Fechan

[bigcguy]

Firstly hello, this is my first post on this forum although i've been lurking for some time.

I'm doing some research for a trail I'm developing along the Taf Fechan valley. Searching the Coflein website i found a dot on their map with this info.
The location is in a field opposite the Glais Mill Taf Fechan, i've walked through this field and not noticed anything canal like, but it probably deserves another look.
Anyone been there, seen it or have any idea where this canal might go??? 1770 is fairly early for a canal - especially right out there !

NPRN
261902
Map Reference
SO00NW
Grid Reference
SO04310953
Unitary (Local) Authority
Merthyr Tydfil
Old County
Glamorgan
Community
Vaynor
Type of Site
CANAL
Broad Class
Industrial
Period
Post Medieval

Site Description
Earthworks of S section of 1770s canal; includes level mouth. Can be traced from railway embankment northwards for c.80m through dense scrub growth & broadleaf. Threat: Land improvement Response: Preserve Vegetation: Scrub / broadleaf

[robertjones]

Strange reference as Vaynor has never been in the Old County Glamorgan and did not become a part of Glamorgan until 1974.
Seems too early I will check the private publication of the Taf Fechan Local history Society.
Rob