The greater part of this parish is situated on granite, including
within its boundaries Roughtor and Brown Willy, the highest hills in
Cornwall, the latter being 1368 feet above the level of the sea. The
composition of this granite has been already noticed under the head of
Advent: it affords few varieties, which may be owing to its offering
few opportunities for examination.
The circumstance most attractive of attention is the great sterility
of this extensive district; some few contracted spots are indeed
brought into cultivation; some parts afford summer pasturage for
cattle, and others turf for fuel; but by far the greater portion of
the whole lies entirely unproductive. And this character belongs to
the whole insulated patch of granite more than ten miles in diameter;
and the church of St. Breward is the only one to be found on this
extensive surface of perhaps from forty to fifty thousand acres; while
nine churches are to be found on the granite district of the Land’s
End, where this substratum, departing from its usual qualities, gives
fertility to the soil.
The western extremity of this parish is fertile, resting on a peculiar
kind of slate, which possesses geological interest. It may be seen at
Combe, at Penrose, and at other places near the river Camel, and
appears to be a variety of mica slate, being composed of granular
felspar, interlaminated with mica. It contains beds of dark purple
felspar rock, very similar to that which abounds in the mining
district in the western part of the county. This micaceous slate
gradually passes into a thick lamellar rock, which extensively
disintegrates and becomes argillaceous, exactly resembling the stone
quarried for building at Bodmin.
[20] This is written in a different hand.