acidulated), mud, and molten earths. Volcanoes are a species of
intermittent spring. Temperature of thermal springs; their constancy and
change. Depth of the foci -- p. 219-224 and notes. Salses, mud volcanoes.
While fire-emitting mountains, being sources of molten earths, produce
volcanic rocks, spring water forms, by precipitation, strata of limestone.
Continued generation of sedimentary rocks -- p. 228 and note.

d. Diversity of volcanic elevations. Dome-like closed trachytic mountains.
Actual volcanoes which are formed from craters of elevations or among the
detritus of their original structure. Permanent connection of the interior
of our earth with the atmosphere. Relation to certain rocks. Influence of
the relations of height on the frequency of the eruptions. Heights of the
cone of cinders. Characteristics of those volcanoes which rise above the
snow-line. Columns of ashes and fire. Volcanic storm during the eruption.
Mineral composition of lavas -- p. 236 and notes. Distribution of volcanoes
on the earth's surface; central and linear volcanoes; insular and littoral
volcanoes. Distance of volcanoes from the sea-coast. Extinction of
volcanic forces -- p. 246 and notes.

e. Relation of volcanoes to the character of rocks. Volcanic forces form
new rocks, and metamorphose the more ancient ones. The study of these
relations leads, by a double course, to the mineral portion of geognosy (the
study of the textures and of the position of the earth's strata), and to the
configuration of continents and insular groups elevated above the level of
the sea (the study of the geographical form and outlines of the different
parts of the earth. Classification of rocks according to the scale of the
phenomena of structure and metamorphosis, which are still passing before our
eyes. Rocks of eruption, sedimentary rocks, changed (metamorphosed) rocks,
conglomerates -- compound rocks are definite associations of
cryctognostically simple fossils. There are four phases in the formative