Geological Observations on South America | Page 4

contain.
Many parts of them are admirably adapted for giving an insight into
problems regarding the structure and changes of the earth's surface, and
in fact they form a charming introduction to physical geology and
physiography in their application to special domains. The books
themselves cannot be obtained for many times the price of the present
volume, and both the general reader, who desires to know more of
Darwin's work, and the student of geology, who naturally wishes to
know how a master mind reasoned on most important geological
subjects, will be glad of the opportunity of possessing them in a
convenient and cheap form.
The three introductions, which my friend Professor Judd has kindly
furnished, give critical and historical information which makes this
edition of special value.
G.T.B.

PLATE I. GEOLOGICAL SECTIONS THROUGH THE
CORDILLERAS.
SECTION 1/1. SECTION OF THE PEUQUENES OR PORTILLO
PASS OF THE CORDILLERA.
SECTION 1/2. SECTION OF THE CUMBRE OR USPALLATA
PASS.
SECTION 1/3. SECTION OF THE VALLEY OF COPIAPO TO THE
BASE OF THE MAIN CORDILLERA.
PLATE II. MAP OF SOUTHERN PORTION OF SOUTH AMERICA.

TABLE OF CONTENTS.
CRITICAL INTRODUCTION.
CHAPTER I.
--ON THE ELEVATION OF THE EASTERN COAST OF SOUTH
AMERICA.
Upraised shells of La Plata.--Bahia Blanca, Sand-dunes and
Pumice-pebbles.- -Step-formed plains of Patagonia, with upraised
shells.--Terrace-bounded valley of Santa Cruz, formerly a
sea-strait.--Upraised shells of Tierra del Fuego.--Length and breadth of
the elevated area.--Equability of the movements, as shown by the
similar heights of the plains.--Slowness of the elevatory
process.--Mode of formation of the step-formed plains.--Summary.-
-Great shingle formation of Patagonia; its extent, origin, and
distribution.--Formation of sea-cliffs.
CHAPTER II.
--ON THE ELEVATION OF THE WESTERN COAST OF SOUTH
AMERICA.

Chonos Archipelago.--Chiloe, recent and gradual elevation of,
traditions of the inhabitants on this subject.--Concepcion, earthquake
and elevation of.- -VALPARAISO, great elevation of, upraised shells,
earth or marine origin, gradual rise of the land within the historical
period.--COQUIMBO, elevation of, in recent times; terraces of marine
origin, their inclination, their escarpments not horizontal.--Guasco,
gravel terraces of.--Copiapo.--PERU.-- Upraised shells of Cobija,
Iquique, and Arica.--Lima, shell-beds and sea- beach on San
Lorenzo.--Human remains, fossil earthenware, earthquake debacle,
recent subsidence.--On the decay of upraised shells.--General
summary.
CHAPTER III.
--ON THE PLAINS AND VALLEYS OF CHILE:--SALIFEROUS
SUPERFICIAL DEPOSITS.
Basin-like plains of Chile; their drainage, their marine origin.--Marks
of sea-action on the eastern flanks of the Cordillera.--Sloping
terrace-like fringes of stratified shingle within the valleys of the
Cordillera; their marine origin.--Boulders in the valley of
Cachapual.--Horizontal elevation of the Cordillera.--Formation of
valleys.--Boulders moved by earthquake- waves.--Saline superficial
deposits.--Bed of nitrate of soda at Iquique.-- Saline
incrustations.--Salt-lakes of La Plata and Patagonia; purity of the salt;
its origin.
CHAPTER IV.
--ON THE FORMATIONS OF THE PAMPAS.
Mineralogical constitution.--Microscopical structure.--Buenos Ayres,
shells embedded in tosca-rock.--Buenos Ayres to the Colorado.--S.
Ventana.--Bahia Blanca; M. Hermoso, bones and infusoria of; P. Alta,
shells, bones, and infusoria of; co-existence of the recent shells and
extinct mammifers.-- Buenos Ayres to St. Fe.--Skeletons of
Mastodon.--Infusoria.--Inferior marine tertiary strata, their

age.--Horse's tooth. BANDA ORIENTAL.-- Superficial Pampean
formation.--Inferior tertiary strata, variation of, connected with
volcanic action; Macrauchenia Patachonica at S. Julian in Patagonia,
age of, subsequent to living mollusca and to the erratic block period.
SUMMARY.--Area of Pampean formation.--Theories of
origin.--Source of sediment.--Estuary origin.--Contemporaneous with
existing mollusca.-- Relations to underlying tertiary strata. Ancient
deposit of estuary origin.--Elevation and successive deposition of the
Pampean formation.-- Number and state of the remains of mammifers;
their habitation, food, extinction, and range.--Conclusion.--Supplement
on the thickness of the Pampean formation.--Localities in Pampas at
which mammiferous remains have been found.
CHAPTER V.
--ON THE OLDER TERTIARY FORMATIONS OF PATAGONIA
AND CHILE.
Rio Negro.--S. Josef.--Port Desire, white pumiceous mudstone with
infusoria.--Port S. Julian.--Santa Cruz, basaltic lava of.--P. Gallegos.--
Eastern Tierra del Fuego; leaves of extinct beech-trees.--Summary on
the Patagonian tertiary formations.--Tertiary formations of the Western
Coast.- -Chonos and Chiloe groups, volcanic rocks
of.--Concepcion.--Navidad.-- Coquimbo.--Summary.--Age of the
tertiary formations.--Lines of elevation.-- Silicified
wood.--Comparative ranges of the extinct and living mollusca on the
West Coast of S. America.--Climate of the tertiary period.--On the
causes of the absence of recent conchiferous deposits on the coasts of
South America.--On the contemporaneous deposition and preservation
of sedimentary formations.
CHAPTER VI.
--PLUTONIC AND METAMORPHIC ROCKS:--CLEAVAGE AND
FOLIATION. Brazil, Bahia, gneiss with disjointed metamorphosed
dikes.--Strike of foliation.--Rio de Janeiro, gneiss-granite, embedded
fragment in, decomposition of.--La Plata, metamorphic and old

volcanic rocks of.--S. Ventana.--Claystone porphyry formation of
Patagonia; singular metamorphic rocks; pseudo-dikes.--Falkland
Islands, palaeozoic fossils of.--Tierra del Fuego, clay-slate formation,
cretaceous fossils of; cleavage and foliation; form of land.--Chonos
Archipelago, mica-schists, foliation disturbed by granitic axis;
dikes.--Chiloe.--Concepcion, dikes, successive formation of.--Central
and Northern Chile.--Concluding remarks on cleavage and
foliation.--Their close analogy and similar origin.--Stratification of
metamorphic schists.--Foliation of intrusive rocks.--Relation of
cleavage and foliation to the lines of tension during metamorphosis.
CHAPTER VII.
--CENTRAL CHILE:--STRUCTURE OF THE CORDILLERA.
Central Chile.--Basal formations of the Cordillera.--Origin of the