f'Kr
Much of it appeared to be slate, but the whole of the upper part is sand-stone. At the
S. W. extremity of the Bay of Concepcion, the ridges to the southward, and behind the
village of Talcahuana, are composed of a loosely cemented and rather #ne sand-stone,
containing some beds of coal. I have been informed that coals abound near the town
of Concepcion, on the south side of the Biobio, towards the sea.
In no part could I perceive any lime-stone rock. As to the fossil beds of shells,
such as exist at the present day in the bay, I observed them of very considerable extent,
and in many situations. They were always immediately under the soil. At one
place, about half a mile north from Talcahuana, they form a stratum on the upper part
of the cliff, nine feet deep at one end, and diminishing in depth for one hundred paces.
Under them is a reddish mould lying upon a micaceous slate. Among the shells Lieutenant
Belcher and myself remarked portions of crabs, flustrai, and echini, and of micaceous
slate and quartz. Many of the same sort of shells, brought to us with the
animals alive in them, prove that they still live in the bay. They form to this day, the
chief food ot the inhabitants of its shores.—C,
E X T R A C T P R O M T H E N O T E S O P L I E U T E N A N T B E L C H E R .
From the town of Penco, formerly the city of Concepcion, (see map and section,
pi. I I . Geology,) the low country to the south-westward, including the Isla de Boguau,
has the appearance of being alluvial. On the surface of the hills are beds of shelL
similar to those found at present in tbe Pacific. These beds vary from three to ten
feet in thickness, and cover the highest parts of land on both sides of the bay, in some
places near a thousand feet above the level of the sea. They may possibly have been
raised by volcanic agency aud earthquakes, to which this part of the country is so liable;
particularly Penco, which was destroyed by an earthquake in 1751.
The sand of the beach at Penco, extending to the mouth of the river, is composed
of siliceous grains mixed with mica. A small bank in the river is formed entirely of a
golden-coloured mica, and was brought by one of my boat’s crew as gold. Inland the
rooks are granite near the city of Concepcion. Proceeding northerly from Penco, the
first cliffs are composed of marl and sand-stone, containing ranch oxide of iron, and of a
siaty texture. Between the layers of the slaty sand-stone there are seams of wood-coal,
varying from one to three inches in thickness : the inclination is l l “ dipping N. He-
posing on the slaty sand-stone is a thick deposit of loose marly alluvium. To this cliff
succeeds a low tract of sandy soil, with small alluvial hills composed of loose marl
through which the inhabitants cut to the depth of eight or ten feet and procure m
inferior small coal. Slill further north is marly clay and loose gray sand stone, con-
taming vegetable remains, and seams of imperfect coal. One seam of coal is four feet
thick. Th e next cliff contains harder marl and better coal. Some we obtained for
the ship near Lirquen Head at D was of inferior quality, and without the addition of
wood or some other inflammable substance would not burn ; mixed with English coal,
in the proportion of one-third English, it answered passably well. Under some red
li, ■!
G E O L O G Y . J g 3
calcareous marl also near U, I met with silioified wood; and between the carbonaceous
and marly strata, crystals of sulphate of iron.
The coast from Lirquen Head to Punta P arra is without variation, composed of
alluvium at the summit, compact grey marl in the middle, and clay-slate at the base.
On the north of P u n ta P a rra , at the cliffs marked G, H , and I, the upper stratum is
alluvial; the next slaty marl and loose earthy sand-stone, containing balls of compact
marl, aud enclosing fossil dicotyledonous wood, shells, and bones. The wood is sometimes
converted to black jasper, and sometimes to carbonate of lime ; it is also perforated
hy a teredo, the perforations being filled with crystallized carbonate of lime as in
the fossil-wood of the London clay. The third stratum is compact marl.
^ On the north of I is a sandy beach, with a long valley extending to the river
Caracol: at tins river the sand is chiefly magnetic iron, and had considerable effect on
the compass. The iron sand is chiefly on the surface of a very fine siliceons sand and
in some places where it had caked by the sun, I found it unmixed of fonr and six inches’
depth. Similar sand occurs also on the beach near Penco, and on the south end o fth e
Bland of Quiriquina, and other parts of the bay. The shore from the Caracol to 'Tome
Head IS sandy, with a slight mixture of mic a ; and the cliffs are chiefly of clav-slate.
Immediately north of Tome Head is a sandy beach, with clay-slate inland. At the
chff marked L, the marly strata recommence. I . The snperstratum alluvial. 2. Loose
quartzy sand. 3. Blue clay approaching fullers’ earth. 4. Bed marl, with balls of calcareous
marl and beds of hard sand-stone, inclination 15“, dipping north. In this cliff
found numerous petrifactions, and two vertebra! about the size of those of an ox (these
have been lost;) also a large ammonite, measuring two feet ten inches in diameter, but
too heavy to be removed ; and some fossil-wood converted into coarse jasper, and containing
veins and nodules of chalcedony. In one specimen the small longitudinal vessels
o fth e wood were filled with iron pyrites. A t the northern extremity of the section, the
vertical slate rocks which form the base of Point Darca are divided from the sand-stone
and alluvium of the hills above and behind it, by a mass of green porphyry and horn-
stone ; and on tbe surface of this porphyry is a bed ofporphyritic pebbles, about a hun-
dred feet above the level of the sea.—B.
V A L P A R A IS O .
The lower hills around Valparaiso rise by abrupt and rocky cliffs from the sea-coast-
aud on both sides of the bay, as well as behind the town, the granite shews itself But
in the head of the bay the country rises gradually at first in a verdant slope, and afterwards
by a more rapid ascent. The road which passes over this ridge to Santiago is in
some places very steep, on a diluvial formation containing numerous boulders. The
surface of these hills is bare in many places, and shews large red patches of soil.—C.
S A L A S -Y -G 0 M E 2 I S L A N D .
This island is three-quarters of a mile long, and about thirty feet high. I t is com
posed of a dark-coloured rock, having a reddish brown tint where it is washed by the
sea. The chff is perpendicular for some feet at the water’s edge, whilst the interior is
.i.:n