in a gaseous form by volcanoes. Many of
these springs are thermal, _i. e._, their temperature is above the mean
temperature of the place, and they rise up through all kinds of rock;
as, for example, through granite, gneiss, limestone, or lava, but are
most frequent in volcanic regions, or where violent earthquakes have
occurred at eras comparatively modern.

The water given out by hot springs is generally more voluminous and less
variable in quantity at different seasons than that proceeding from any
others. In many volcanic regions, jets of steam, called by the Italians
"stufas," issue from fissures, at a temperature high above the boiling
point, as in the neighborhood of Naples, and in the Lipari Isles, and
are disengaged unceasingly for ages. Now, if such columns of steam,
which are often mixed with other gases, should be condensed before
reaching the surface by coming in contact with strata filled with cold
water, they may give rise to thermal and mineral springs of every degree
of temperature. It is, indeed, by this means only, and not by
hydrostatic pressure, that we can account for the rise of such bodies of
water from great depths; nor can we hesitate to admit the adequacy of
the cause, if we suppose the expansion of the same elastic fluids to be
sufficient to raise columns of lava to the lofty summits of volcanic
mountains. Several gases, the carbonic acid in particular, are
disengaged in a free state from the soil in many districts, especially
in the regions of active or extinct volcanoes; and the same are found
more or less intimately combined with the waters of all mineral springs,
both cold and thermal. Dr. Daubeny and other writers have remarked, not
only that these springs are most abundant in volcanic regions, but that
when remote from them, their site usually coincides with the position of
some great derangement in the strata; a fault, for example, or great
fissure, indicating that a channel of communication has been opened with
the interior of the earth at some former period of local convulsion. It
is also ascertained that at great heights in the Pyrenees and Himalaya
mountains hot springs burst out from granitic rocks, and they are
abundant in the Alps also, these chains having all been disturbed and
dislocated at times comparatively modern, as can be shown by independent
geological evidence.

The small area of volcanic regions may appear, at first view, to present
an objection to these views, but n