xxvi., s. 81-88).
The Peak of Teneriffe, for instance, is a central volcano, being the central
point of the volcanic group to which the eruption of Palma and Landerote may
be referred. The long, rampart-like chain of the Andes, which is sometimes
single, and sometimes divided into two or three parallel branches, connected
by various transverse ridges, presents, from the south of Chili to the
northwest coast of America, one of the grandest instances of a continental
volcanic chain. The proxiimity of
p 239
active volcanoes is always manifested in the chain of the Andes by the
appearance of certain rocks (as dolerite, melaphyre, trachyte, andesite, and
dioritic porphyry), which divide the so-called primitive rocks, the
transition slates and sandstones, and the stratified formations. the
constant recurrence of this phenomenon convinced me long since that these
sporadic rocks were the seat of volcanic phenomena, and were connected with
volcanic eruptions. At the foot of the grand Tunguragua, near Penipe, on
the banks of the Rio Puela, I first distinctly observed mica slate resting
on granite, broken through by a volcanic rock.
In the volcanic chain of the New Continent, the separate volcanoes are
occasionally, when near together in mutual dependence upon one another; and
it is even seen that the volcanic activity for centuries together has moved
on in one and the same direction, as for instance, from north to south in
the province of Quito.
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