very little worthy of description. Fernando Noronha is situated in the
Atlantic Ocean, in latitude 3 degrees 50 minutes S., and 230 miles distant
from the coast of South America. It consists of several islets, together
nine miles in length by three in breadth. The whole seems to be of volcanic
origin; although there is no appearance of any crater, or of any one
central eminence. The most remarkable feature is a hill 1,000 feet high, of
which the upper 400 feet consist of a precipitous, singularly shaped
pinnacle, formed of columnar phonolite, containing numerous crystals of
glassy feldspar, and a few needles of hornblende. From the highest
accessible point of this hill, I could distinguish in different parts of
the group several other conical hills, apparently of the same nature. At
St. Helena there are similar, great, conical, protuberant masses of
phonolite, nearly one thousand feet in height, which have been formed by
the injection of fluid feldspathic lava into yielding strata. If this hill
has had, as is probable, a similar origin, denudation has been here
effected on an enormous scale. Near the base of this hill, I observed beds
of white tuff, intersected by numerous dikes, some of amygdaloidal basalt
and others of trachyte; and beds of slaty phonolite with the planes of
cleavage directed N.W. and S.E. Parts of this rock, where the crystals were
scanty, closely resembled common clay-slate, altered by the contact of a
trap-dike. The lamination of rocks, which undoubtedly have once been fluid,
appears to me a subject well deserving attention. On the beach there were
numerous fragments of compact basalt, of which rock a distant facade of
columns seemed to be formed.

TERCEIRA IN THE AZORES.

The central parts of this island consist of irregularly rounded mountains
of no great elevation, composed of trachyte, which closely resembles in
general character the trachyte of Ascension, presently to be described.