most conspicuous within the limits of the United States,—but
also for its minerals, its climate, its peculiar geological features,
its remarkable forests, its scenery, and the comparative density of
the population along its western flank. Its importance and interest
are still farther enhanced if (as on the whole seems a reasonable
thing to do) we consider the Cascade range as being a continuation.
The Sierra Nevada proper forms the western edge of the widest and
highest portion of the Cordilleras, or that portion which lies east of
the State of California. It is especially conspicuous from the western
side, because on this side it falls nearly to the level of the sea, while
on the other side it sinks only to the general plateau level. It does
not, however, border the Pacific directly, since there is, all along
its course, a lower system of mountains, rising directly from the
coast—the so-called Coast ranges. With these the Sierra Nevada
and the Cascade range are so inosculated in certain portions of
their extent that a topographical separation of them is impossible,
but for a considerable distance both the Sierra and the Cascade
range are distinctly separated from the Coast ranges by broad low
valleys, the most extensive of these being the Great Valley of
California (for which, as well as for the more important features of
the Californian Sierra, the reader is referred to Ency. Brit., vol. iv.
pp. 696-8). The Sierra Nevada has been already shown to be made
up of a core of eruptive granite flanked by rocks of Mesozoic age;
the development of these Mesozoic rocks increases towards the
north, and in the region lying along the western declivity of the
chain, in the central portions of the State, forms the auriferous belt
of the Sierra. The gold-producing detrital deposits, formerly so
extensively worked, are gravels of Tertiary age covered more or
less completely by volcanic materials, which not unfrequently
attain a thickness of several hundred feet. As in other portions of
the Cordilleran region, the presence of eruptive rocks of Tertiary
and post-Tertiary age is a fact of great importance. The volcanic
materials in question are seen in places in large masses on almost
the very highest portion of the Sierra, in its southern extension,
in a region where there is very little of this material lower down
on the flanks of the range, and where there are no slates and no
mining or washing for gold of any importance. Just south of the
Mount Whitney group, where the Sierra rapidly falls off in height
between the two ranges of which the system is here comprised,
there is a region—the valley of the Kern river—in which occur
several volcanic cones, which have a very recent look, but which
are not known to have been in eruption since the advent of the
whites. This region, however, for several years in succession—from
1870 onwards, and perhaps from an earlier date—appears, on
good evidence, to have been repeatedly and violently disturbed by
earthquakes; and this seems also to have been the portion of the
Sierra which was most affected by the great earthquake of March
26, 1872. Midway in Owen's Valley, on the east side of the Sierra,
beginning about 30 miles north of Lone Pine, where this earthquake
was most disastrous in its effects, there is a region of volcanic
cones and lava-flows, by which the river is crowded over against
the Inyo range, at the foot of which it has only just room to flow.
These cones are seemingly as perfect as they ever were; and the
flows of basalt have spread themselves out over the sage-brush
slope in a manner indicative of a very recent date for their
outbreaking. Yet all seem now to be entirely dormant. Even
solfataric action is almost (if not quite) exclusively manifested at
the present time at or near the summits of the highest volcanic
cones of the Sierra and the Cascade range. Farther north more
and more volcanic materials cover the western flank of the range;
and from about 39° 30′ N. lat. much the larger portion of the
older rocks is overlain and concealed by modern eruptive materials,
through which the streams have worn channels, often of great depth,
from the sides of which access is given to the auriferous gravels
occupying the bottoms of the channels of the old Tertiary but now
buried river-systems. In Lassen's Peak, in 40° 30′ N. lat., we
have the first exhibition of the isolated volcanic cone rising high
above the adjacent country, which makes so prominent a feature
of the range farther north in California and through Oregon and
Washington Territory. This volcanic mass is 10,537 feet in height,
and there are abundant signs of recent volcanic activity on and near
it. There are, in this vicinity, several localities where hot springs
occur, and where the rock has been so softened by solfataric action
as to have given rise to mud lakes, in which jets of hot water and
mud are sometimes thrown to a height of several feet. One of
these places, about 8 miles from the summit of the peak, is 5976
feet above the sea, and there is here a pool of hot water 600 feet
long by 300 broad, in the midst of which miniature mud volcanoes
are being constantly formed. There are no such striking indications
of dormant volcanic activity as are seen in the vicinity of
Lassen's Peak anywhere to the southward along the crest and flanks
of the Sierra. Neither is it known that there has been anything
which could be properly called an eruption, whether of lava or
ashes, since the region was first visited by the whites, either from
Lassen's Peak or from the much grander volcano to which the
name of Shasta is given. At Lassen's Peak a great change takes
place in the character of the range, which is here broken through
transversely by a great fault, to the south of which we have the
high ranges and deep cañons often cut down through the volcanic
strata, and sunk deeply into the underlying metamorphic rocks,
while to the north is a great depression, comparatively level, and
exclusively occupied by volcanic rocks, which stretch off to the
north and north-east, in almost unbroken continuance, for many
hundred miles, forming a portion of the northern plateau region
already described. Seventy miles north-west of Lassen's Peak rises
Mount Shasta (14,440 feet), standing in remarkable isolation on a
base between 10,000 and 11,000 feet lower than its summit. There
are indications of former volcanic activity near the summit, but
they are not so marked as those on and near Lassen's Peak. There
is a flat area about 400 feet below the summit, on one side of which
are several orifices from which steam and sulphurous gases were
constantly escaping at the time of the present writer's ascent of
the mountain (1862).
Cascade range.North of Mount Shasta the mountain mass now called the Cascade range maintains characters similar to those which it has between Lassen's Peak and Shasta for a distance of fully 500 miles, or until we have passed the northern boundary of the United States. The principal continuous ridge is comparatively low, and on it at irregular intervals rise great volcanic cones, differing considerably from each other in elevation, but all much higher than the surrounding plateau-like base on which they are built up. Unfortunately no portion of the Cascade range has as yet been topographically surveyed. From Mount Shasta northwards there are several prominent peaks, which are apparently volcanic, but which have not the conical form, while others exhibit this peculiar feature in a high degree of perfection. Mount Pitt (9718 feet) is a well-defined cone, about 75 miles north of Shasta. Mount Jefferson, about 150 miles still farther north, is of a similar character; and between Pitt and Jefferson are various prominent peaks, especially the highly picturesque group of five sharp points, known as the Three Sisters, only three of them being visible from the Willamette Valley. All through this portion of the range evidences of comparatively recent volcanic action are present, in the form of regular craters and outflows of lava. Somewhat less than 100 miles north of Mount Jefferson is the grand break made in the Cascade range by the Columbia river, which has cut entirely through the volcanic mass, down almost to the level of the sea,—the Dalles, on the eastern side of the range, having an elevation of only about 100 feet. At the Dalles—so named on account of the great, broad, flat plates or sheets of lava which are there well exhibited on and near the river—is the beginning, in this direction, of the volcanic plateau of the Columbia. Near this point rise three of the best-defined volcanic cones of the range, two—Mount Adams and Mount St Helens—on the north side of the river, and one—Mount Hood on the south. The last-named has been found by barometric measurement to be 11,225 feet; the other two seem to be of nearly equal height (about 10,500 feet). Mount Rainier (14,444 feet)—about 75 miles north of the Columbia river—is rivalled in the whole of the Cascade range by Shasta only. The views of Rainier from Puget Sound are magnificent. It is much less accessible than Shasta, as it lies in the midst of a dense forest, far from roads; it is also very much more deeply covered with snow and ice. Still farther north than Rainier, and near the boundary line of the United States, is Mount Baker (10,755 feet), a prominent object in the grand panoramic view from Victoria, Vancouver Island. While evidences of comparatively recent volcanic action are so conspicuous all along the range from Lassen's Peak north to Mount Baker, it is not easy to reconcile the conflicting evidence with regard to the present condition of the eruptive agencies. The present writer, during several years of exploration, found no evidence whatever of any recent outflow of melted lava, such as would harden into a solid rock on cooling, in any part of the Sierra Nevada or the Cascade range. The eruptive rocks of these ranges are mainly andesites; but the last outflow of molten rock appears to have been basaltic in character. This is certainly true for the Sierra Nevada, and probably so for the Cascade range. Under the basalt we find, in the buried sedimentary strata, abundant remains of vegetation, pronounced by competent authority to be Pliocene in age, with a few species intermingled which have a decidedly Miocene character. The animal remains found under the basaltic lava are all of extinct species, with the single exception of man, whose bones or handiwork have been repeatedly taken from strata occupying this geological position. The age of the sedimentary beds under the basalt is therefore Tertiary, from the combined evidence of both plants and animals. There is no evidence that fragmental lava—ashes, cinders, and the like—has been emitted from any one of the volcanic cones of the Sierra Nevada since the region became known to the whites; but there is abundant evidence to this effect in regard to some of the high points in the Cascade range. Mount Baker seems to have furnished the most unquestionable proof of activity in recent times. The first known eruption of this volcano appears to have taken place in 1843. In at least three later instances Mount Baker has been seen in eruption by men of un-
