not cgnsider this indurated mud-like matter, which is generally
charged with basaltic pebbles and fragments, as originating in the
decomposition of the basalt itself, but rather to have béèn created
in the crater by a different proportion of the constituent elements,
and to have flowed from it, intermingled with the streams of basalt.
The yellow tufa, which is here above the basalt; is thickly sprinkled
with small pumice-stones. The cassia accuminata covers the road
side in all directions, mingled with cacti, pelargonio, roses, fig-trees,
and ivy; four or five small dragon-trees add to the variety. Having
ascended about 2000 feet above the sea, we meet with plantations
of the pinus sylvestris, which are said to have bfeen made, with the
view of binding the loose red soil, which would otherwise be scattered,
and slide away over the cliffs in the rainy season. The deep
red tufa, however, which forms this soil, and which rests on the
yellow, seems to be more aluminous here than on the wèstern side,
and firmer ; perhaps from the number of basaltic dikes which intersect
it, running towards the sea, and generally presenting a
series of dose horizontal fractures, as if it had not flowed very
rapidly into the rents of the tufa, but was deposited in layers;
Masses of basalt crown the tops of all the hills, but axe in no
instance columnar ; and the remnants of streams of basalt connected
with these .masses; and descending over the tufa into the sea, are
constantly evident; Descending the ravine from which the path
to the summit of the Brazen Head branches off, the red tufa,
which just above it had been full of large nodules of basalt, appears
to be charged with a kind of pumice grit, and dips S.S.W. in an
angleTof 30°; a qptural cross section at your back, running east and
west, discloses this tufa in horizontal layers with the basalt above it.
Looking down at the Brazen Head, from the lofty cliff adjoining
it on the west,, we observe large masses , of columnar, mixed, with
angular, irregular pieces of basalt; (sometimes scoriaceous)' imbedded
in red tufa. The grand slip to the south will be best