The course of an ancient leat which once fed a small hushing pond located within
the prehistoric opencast has been traced over a distance of 500 m from its source,
the latter within a small embayment at the head of the Nant yr onnen stream (at 483
m OD). This channel was archaeologically sectioned in 1993 at 3 different locations.
From one of these sections close to the source of the leat a sample of buried peat
within its base was radiocarbon dated to 1190 – 1290 yrs cal AD. This date must relate
to a time after its abandonment. All that we can really say now is that the leat
is at least Early Medieval, but could be earlier (perhaps Roman).
The remains of a late hushing pond and turfstack dam at the front of the infilled
opencast were examined in 1989. The old ground-surface (grass layer) found beneath
the last turf dam to be built has been radiocarbon dated to between 1430-1620 AD,
suggesting that hushing activities carried out on the Comet Lode in order to remove
earlier mine spoil and to expose the mineral vein beneath continued well into the
early postmedieval period. By then the source of the water was probably within the
peat bogs located on the moorland above.