20 miles from the nearest ocean--an important circumstance,
as showing that the proximity of the sea is not a necessary condition,
although certainly a very general characteristic of the position of
active volcanoes. The extraordinary eruption of this mountain, in 1759,
will be described in the sequel. If the line which connects these five
vents be prolonged in a westerly direction, it cuts the volcanic group
of islands called the Isles of Revillagigedo.

To the north of Mexico there are said to be three, or according to
some, five volcanoes in the peninsula of California; and a volcano is
reported to have been in eruption in the N. W. coast of America, near
the Colombia river, lat. 45 degrees 37 minutes N.

_West Indies._--To return to the Andes of Quito: Von Buch inclines to
the belief that if we were better acquainted with the region to the east
of the Madalena, and with New Granada and the Caraccas, we might find
the volcanic chain of the Andes to be connected with that of the West
Indian or Carribee Islands. The truth of this conjecture has almost been
set at rest by the eruption, in 1848, of the volcano of Zamba, in New
Grenada, at the mouth of the river Madalena.[475]

Of the West Indian islands there are two parallel series: the one to the
west, which are all volcanic, and which rise to the height of several
thousand feet; the others to the east, for the most part composed of
calcareous rocks, and very low. In the former or volcanic series, are
Granada, St. Vincent, St. Lucia, Martinique, Dominica, Guadaloupe,
Montserrat, Nevis, and St. Eustace. In the calcareous chain are Tobago,
Barbadoes, Mariegallante, Grandeterre, Desirade, Antigua, Barbuda, St.
Bartholomew, and St. Martin. The most considerable eruptions in modern
times have been those of St. Vincent. Great earthquakes have agitated
St. Domingo, as will be seen in the twenty-ninth chapter.

I have before mentioned (p. 270) the violent earthquake which in 1812
convulsed the valley of the Mississippi at New Madrid, for the space of
300 miles in length, of which more will be said in the twenty-seventh
chapter. This happened exactly at the same time as the great earthquake
of Caraccas, so that it is possible that these two points are parts of
one subterranean volcanic region. The island of Jamaica, with a tract of
the contiguous sea, has often experienced tremendous shocks; and these
are frequent along a line extending from Jamaica to St. Domingo and
Porto