87 
HOLY ISLAND (see Map V.).— The Holy Island mussel beds, 
which occur on Fenliam Flats, between the island and the main- 
land, occupy the largest area of any of the Northumberland beds. 
The flats consist of a large expanse of muddy sand with stretches 
of gravel, overlying sandstones, shales, and limestones of the 
Carboniferous Limestone series ; the basaltic dyke (the Holy Island 
Dyke) which runs through these strata being too narrow to be 
taken into account for the present purpose. Most of the flats are 
uncovered at low tide, but certain parts are always covered. Small 
burns from the mainland run across the flats, and thus a mixture 
of fresh and salt water is effected. The mussels occur chiefly on 
the more gravelly ground, and are separated from Holy Island by 
comparatively deep water even at the lowest tides. The best 
specimens are to be found on the Oyster Scaup, and stretch out for 
some way south over Madges’ Batts and south-west to within about 
a third of a mile from the mainland. There are no good mussels 
east of the scaup except on the slakes, which are from half a mile 
to a mile from the mainland opposite Holy Island. One of the 
deeper channels of water cuts the scaup off from the sandy and 
muddy flat which separates Holy Island from the mainland, and 
can be crossed on foot at half tide. In this sandy part very small 
mussels are sometimes seen covering the ground, having been 
swept there by the tide, but these soon die, probably being un- 
covered for too long a time, and having no proper shelter. The 
slakes also yield mussels, but not of such good quality as those 
from the scaup. The ground here is soft and dangerous and 
covered with sea-grass, the mussels occurring at intervals in large 
patches by the Foulwork Burn (on both sides) and by Mill Burn. 
People walking along this part sink into the mud from four to 
fifteen inches. The fishermen come here for bait when the scaup 
is not uncovered, and sometimes transplant the mussels to the 
scaup to fatten and grow to a larger size. Hen Pool — a small pool 
near the Beacons, surrounded by sand and always having sea-water 
in it — contains very good mussels, which grow well, although no 
fresh water, except rain, ever reaches it, and the mussels are never 
uncovered. The sea enters this pool about two hours before high 
Avater. Another bed is located between the island and the main- 
land to the north, at the end of the Snook, but here the blowing 
sand often destroys the mussels, choking them up and killing them. 
A large stretch of these shells in this place looks at first sight like a 
flourishing mussel bed, but when closely examined all the shells 
