pressure beneath the crust find a way of escape; and
thus the structure of the globe is preserved from even greater
convulsions than those which from time to time take place at various
points on its surface. This girdle is partly terrestrial, partly
submarine; and commencing at Mount Erebus, near the Antarctic Pole,
ranging through South Shetland Isle, Cape Horn, the Andes of South
America, the Isthmus of Panama, then through Central America and Mexico,
and the Rocky Mountains to Kamtschatka, the Aleutian Islands, the
Kuriles, the Japanese, the Philippines, New Guinea, and New Zealand,
reaches the Antarctic Circle by the Balleny Islands. This girdle sends
off branches at several points. (See Map, p. 23.)

[Illustration: Fig. 3.--Volcanic cone of Orizaba (Cittaltepeth), in
Mexico, now extinct; the upper part snow-clad, and at its base forest
vegetation; it reaches a height of 16,302 Parisian feet above the
sea.--(After A. von Humboldt.)]

(_a._) The linear arrangement of active or dormant volcanic vents has
been pointed out by Humboldt, Von Buch, Daubeny, and other writers. The
great range of burning mountains of the Andes of Chili, Peru, Bolivia,
and Mexico, that of the Aleutian Islands, of Kamtschatka and the Kurile
Islands, extending southwards into the Philippines, and the branching
range of the Sunda Islands are well-known examples. That of the West
Indian Islands, ranging from Grenada through St. Vincent, St. Lucia,
Martinique, Dominica, Guadeloupe, Montserrat, Nevis, and St. Eustace,[1]
is also a remarkable example of the linear arrangement of volcanic
mountains. On tracing these ranges on a map of the world[2] (Map, p.
23), it will be observed that they are either strings of islands, or lie
in proximity to the ocean; and hence the view was naturally entertained
by some writers that oceanic water, or at any rate that of a large lake
or sea, was a necessary agent in the production of volcanic eruptions.
This view seems to receive further corroboration from the fact that the
interior portions of the continents and large islands such as Australia
are destitute of volcanoes in action, with the remarkable exceptions of
Mounts Kenia and Kilimanjaro in Central Africa, and a few others. It is
also very significant in this connection that many of the volcanoes now
extinct, or at least dormant, both in Europe and Asia, appear to have
been in proximity to sheets of water during the period of activity. Thus
the old volcanoes