nounced the nodules containing the .galéolaria, to have been
amygdaloidal, the remains of this tubicola having at first sight all
the appearance of an earth, subsequently deposited in the pores
of the basalt. Very small balani also adhered to these nodules.
I met with two species of trochm on the same shore, and the turbo
edulis, which adheres to the rocks, and is generally eaten by the
natives: two species of helix % lay upon the rocks out of reach of
the sea; the animals had left the shells, which had probably been
rolled down from the top of the cliff“. In a recess upwards of 150
feet from the sea, and nearly as high above its- level, I was surprised
to find rows of stalactites of muriate of Soda, frequently a
foot long, pendant from the red tufa like so many icicles, and
terminating in nodules of the same salt, as large as the half of a
duck’s egg. Breaking off some of the masses, the salt appeared to
be spread over the interior surface, as if the tufa was impregnated
with it; nor is this improbable, when we recollect, that M, Brieslak*
has seen muriate of soda efflorescing from volcanic tufas, in situations
very, distant from the sea, and that it abounds in such quantities
in the crater, and in the lava streams of Vesuvius, according
to M. Menard de la Groye', that the peasants load themselves with
it for their domestic purposes*. The yellow tufa close to the sea,
was merely sprinkled with saline particles, like a fine powder,
evidently deposited by the spray.
i Sailing from Funchal along the eastern coast to the Brazen
Head, we first find the basalt (frequently rudely columnar above,
and bellying out like the sails of a ship) above the tufa and scoriae.
8 They both belong to the sub-genus helicella (Gr. aplostonue) ,pf De Ferrussac,
but I suspect they are new species.
h Introduction à la Géologie, p. 426.
h D’Aubuisson, Traité de fieognosie, t. 2, p. 595.
k Baron de Humboldt found salt disseminated in a clay formation in the Cordillieres,
nearly 13,000 feet above the sea. Relation Historique, 1. 2, c. 5.
Beyond the fort and village are one or two alternations of the
basalt and red tufa, the former being uppermost; and this leads
to the lofty cliffs, composed of a basalt with- horizontal fractures,
which sometimes appears, from decomposition, to be imbedded in
red earth, and is covered by shallow, cork-like layers of tufaf All
these cliffs have no doubt been produced by the' combined attacks
of the ocean and atmosphere. The deeply inclined planes, naturally
created by volcanic streams flowing from a central and
elevated crater to the sea, were first worn away by its waters at
their base; shallow vertical depths being formed in the first
instance, the sea continued to undermine, whilst the atmosphere
decomposed, and the crumbling summits of these cliffs being, from
the continued aetion of the sea below, gradually brought to overhang
the base, avalanches ensued, which increased their face or
depth. Close to the Cabo Garajao, the basalt descends considerably,
and the deposit of tufas above it becomes very deep. East
of the Brazen Head, there are several basalt dikes descending
through the tufa, some of which have evidently been formed before
the slips ; and the basalt in some places presents a series of concentric
circles, as if it had formed a small whirlpool when in the
fluid state. It seems very evident, that these dikes are in no
instance injections of basalt from beneath, but have been formed
by streams filling up those cracks arid gaps in the tufa, created by
the convulsions preceding an eruption, and by the slips resulting
from the partial giving way of former deposits. In descending
from Pico Ruivo, I saw two dikes (5000 feet above the sea) uniting
above, like the prongs of a pitch-fork, which it would be difficult
to explain, but as a downward stream. The tufa, in the vicinity
of these dikes, is naturally harder and firmer than that-to the west-'
ward. We next pass Santa CruZ, which lies in a fine break,
uninvaded by the streams of the upper basalt, with Pico Camacha,
a little to the west of its bed, Pico Moraynya, (beautifully wooded)
K