

20p piece to show size of marking.
June 2003
from
Journal of the Royal institution of Cornwall Volume 10, page 190.
Groups of pits or hollows on sloping rock on the shore of the Gannel at “B” in the map Figures signify diameter in inches.
from
Journal of the Royal institution of Cornwall Volume 10, page 190.
Apparently these rock markings are best reached from the River Gannel by boat. There are not far from a place known as the Fern pit. This place is easy to find as there is a small ferry that operates from this point across to Crantock beach.
ps
The Gannel is tidal and a dangerous place to swim or wade, in order to walk right around the estuary you will need to avoid high tide.