re-appear as the islets of the Steep and Flat Holms. On their S.W. side
they descend into the plain with considerable abruptness; and when
viewed from the lower parts of the county, present a hard sky-line,
like some enormous earthwork. On the opposite side their aspect in
general is far less impressive, and towards Bath they lose themselves
in a confusion of elevations and declivities. The main ridge is an
extended tableland, some 25 m. long, and in places 3 m. broad. It rises
to its greatest heights at Blackdown (1067 ft.) and Masbury (958).
Geologically, it consists of mountain limestone superimposed on old red
sandstone, which here and there comes to the surface. Near Downhead
there is an isolated outburst of igneous rock. The Mendips are
honeycombed with caverns, the most notable being at Banwell, Harptree,
and Burrington; and a large one has been recently discovered some 4 m.
from Wells. At Cheddar their W. edge is broken by a remarkable gorge,
in the sides of which caves also occur. The level of the tableland is
indented with "swallet holes," the chief of which are the East Water
Swallet and the Devil's Punch-Bowl. The _Quantocks_ are much less
extensive, though their highest summits rise to a greater altitude.
Like the Mendips, they turn their steepest flank westwards, the ascent
on the E. being gradual; and on this side they are cut by a number of
well-timbered and delightful combes. Few caves have been discovered in
them, though there is one at Holwell near Asholt. W. of the Quantocks
are the _Brendons_ and the highlands of _Exmoor_, the latter extending
into Devon, though their highest point, Dunkery Beacon, is included in
Somerset. Dunkery is 1707 ft. above the sea-level; and other
conspicuous hills in this district are Lucott Hill (1516), Elworthy
Barrow (1280), Selworthy Beacon (1014), and Grabbist Hill. The
Quantocks, Brendons, and Exmoor consist of older rocks than the
Mendips, belonging as they do to the Devonshire series of old red
sandstones. Bordering the Brendons are found the red marls of the