162 
GEOLOGY. 
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 fine 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 ex- 
tent, 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 upou a micaceous slate. Among the shells Lieu- 
tenant Belcher and myself remarked portions of crabs, flustras, and echini, and of mica- 
ceous 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 of the inhabitants of its shores. — C. 
EXTRACT FROM THE NOTES OF LIEUTENANT BELCHER. 
From the town of Penco, formerly the city of Concepcion, (see map and section, 
pi. II. Geology,) the low country to the south-westward, including the Isla de Roguan, 
has the appearance of being alluvial. On the surface of the hills are beds of shells 
similar to those found at present in the 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 and 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 
rocks are granite near the city of Concepcion. Proceeding northerly from Penco, the 
first cliffs are composed of marl and sand-stone, containing much oxide of iron, and of a 
slaty 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 11° dipping N. Re- 
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 an 
inferior small coal. Still further north is marly clay and loose gray sand stone, con- 
taining vegetable remains, and seams of imperfect coal. One seam of coal is four feet 
thick. The 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 
