The object of the present Introduction, is briefly to describe the
principal localities, from which the Zoological specimens, collected
during the voyage of the Beagle, were obtained. At the conclusion of
this work, after each species has been separately examined and
described, it will be more advantageous to incorporate any general
remarks. The Beagle was employed for nearly five years out of England;
of this time a very large proportion was spent in surveying the coasts
of the Southern part of South America, and of the remainder, much was
consumed in making long passages during her circumnavigation of the
globe. Hence nearly the entire collection, especially of the animals
belonging to the higher orders, was procured from this continent; to
which, however, must be added the Galapagos Archipelago, a group of
islands in the Pacific, but not far distant from the American coast. The
localities may be briefly described under the following heads.
BRAZIL. This country presents an enormous area, supporting the most
luxuriant productions of the intertropical regions. It is composed of
primary formations, and may be considered as being hilly rather than
mountainous. LA PLATA includes the several provinces bordering that
great river;—namely, Buenos Ayres, Banda Oriental, Santa Fé, Entre Rios,
&c. My collections were chiefly made at BUENOS AYRES, at MONTE VIDEO,
the capital of Banda Oriental, and at MALDONADO, a town in the same
province, situated on the northern shore, near the mouth of the estuary
of the Plata. These countries consist either of an undulating surface,
clothed with turf, or of perfectly level plains with enormous beds of
thistles. Except on the banks of the rivers, trees nowhere grow; there
are, however, thickets in some of the valleys, in the more hilly parts
of Banda Oriental. During the winter and spring of this hemisphere, a
considerable quantity of rain falls, and the plains of turf are then
everywhere verdant; but in summer the country assumes a brown and
parched appearance.
BAHIA BLANCA forms a large bay, in latitude 39° S. on a part of the
coast, which falls within the territory of the province of Buenos Ayres,
but which from its physical conditions would more properly be classed
with Patagonia. The tertiary plains of PATAGONIA, extend from the Strait
of Magellan to the Rio Negro, which is commonly assumed as their
Northern boundary. This space of more than seven hundred miles in
length, and in breadth reaching from the Cordillera to the Atlantic
Ocean, is everywhere characterised by the dreary uniformity of its
landscape. Nearly desert plains, composed of a thick bed of shingle, and
often strewed over with sea-shells, (plainly indicating that the land
has been covered within a recent period by the sea,) are but rarely
interrupted by hills of porphyry, and other crystalline rocks. The
plains support scattered tufts of wiry grass, and stunted bushes; whilst
in the broad flat-bottomed valleys, dwarf thorn-bearing trees, barely
ornamented with the scantiest foliage, sometimes unite into thickets;
and here the few feathered inhabitants of these sterile regions resort.
There is an extreme scarcity of water; and where it is found, especially
if in lakes, it is generally as salt as brine. The sky in summer is
cloudless, and the heat in consequence, considerable; whereas the frosts
of winter are, sometimes, severe. The principal localities visited by
the Beagle, were the RIO NEGRO, in latitude 41° S., PORT DESIRE, PORT
ST. JULIAN, and SANTA CRUZ. At the latter place, a party, under the
command of Captain FitzRoy, followed up the river in boats, to within a
few miles of the Cordillera; and an opportunity was thus afforded of
verifying the nature of the country in its entire breadth. At the Rio
Negro the plains are much more thickly covered with bushes, (chiefly
acacias,) than in any other part of Patagonia.
TIERRA DEL FUEGO may be supposed to include all the broken land south of
a line joining the opposite mouths of the Strait of Magellan. The land
is mountainous, and may be aptly compared to a lofty chain, partly
submerged in the sea;—bays and channels occupying the position of
valleys. The Eastern side almost exclusively consists of clay-slate; the
Western, of primary, and various plutonic formations. The mountains,
from the water’s edge, to within a short distance of the lower limit of
perpetual snow, are everywhere (excepting on the exposed western shores)
concealed by an impervious forest, the trees of which do not
periodically shed their leaves. On the East coast, the outline of the
land shows that tertiary formations, like those of Patagonia, extend
south of the Strait of Magellan; but with the exception of this part, it
is rare to find even a small space of level ground; and where such
occurs, a thick bed of peat invariably covers the surface. The climate
is of that kind which has been denominated insular: the winters are far
from being excessively cold, whilst the summers are gloomy, boisterous,
and seldom cheered by the rays of the sun. In all seasons, a large
quantity of rain falls. Hence, from the physical conditions of Tierra
del Fuego, all the land animals must live either on the sea-beach, (and
in this class the Aborigines may be included) or within the humid and
entangled forests.
The FALKLAND ISLANDS are situated in the same latitude as the Eastern
entrance of the Strait of Magellan, and about 270 miles East of it. The
climate is nearly the same as in Tierra del Fuego, but the surface of
the land, instead of being as there, concealed by one great forest, does
not support a single tree. We see on every side a withered and coarse
herbage, with a few low bushes, which spring from the peaty soil of an
undulating moorland. Scattered hills, and a central range of quartz
rock, protrude through formations of clay-slate and sand-stone
(belonging to the Silurian epoch,) which compose the lower country.
The structure of the west coast of South America, from the Strait of
Magellan northward to latitude 38°, in its greater part, (as far north
as Chiloe) is very similar to that of Tierra del Fuego. The climate
likewise is similar,—being gloomy, boisterous, and extremely humid; and,
consequently, the land is concealed by an almost impenetrable forest. In
the northern part of this region, the temperature of course is
considerably higher than near the Strait of Magellan; but nevertheless
it is much less so, than might have been anticipated from so great a
change in latitude. Hence, although the vegetation of this northern
district presents a marked difference when compared with that of the
southern; yet the zoology in many respects has, like the general aspect
of the landscape, a very uniform character. The specimens were chiefly
collected from the PENINSULA OF TRES MONTES, the CHONOS ARCHIPELAGO
(from latitude 46° to 43° 30′), CHILOE with the adjoining islets, and
VALDIVIA. The contrast between the physical conditions and productions
of the East and West coasts of this part of South America is very
remarkable. On one side of the Cordillera, great heavy clouds are driven
along by the western gales in unbroken sheets, and the indented land is
clothed with thick forests; whilst on the other side of this great
range, a bright sky, with a clear and dry atmosphere, extends over wide
and desolate plains.
CHILE in the neighbourhood of CONCEPCION (latitude 36° 42′ S.) may be
called a fertile land; for it is diversified with fine woods, pasturage,
and cultivated fields. But towards the more central districts (near
VALPARAISO and SANTIAGO) although by the aid of irrigation, the soil in
the valleys yields a most abundant return, yet the appearance of the
hills, thinly scattered with various kinds of bushes and cylindrical
Opuntias, bespeaks an arid climate. In winter, rain is copious, but
during a long summer of from six to eight months, a shower never
moistens the parched soil. The country has a very alpine character, and
is traversed by several chains of mountains extending parallel to the
Andes. These ranges include between them level basins, which appear once
to have formed the beds of ancient channels and bays, such as those now
intersecting the land further to the south. North of the neighbourhood
of Valparaiso, the climate rapidly becomes more and more arid, and the
land in proportion desert. Beyond the valley of COQUIMBO (latitude 30°.)
it is scarcely habitable, excepting in the valleys of Guasco, Copiapó,
and Paposa, which owe their entire fertility to the system of
irrigation, invented by the aboriginal Indians and followed by the
Spanish colonists. Northward of these places, the absolute desert of
Atacama forms a complete barrier, and eastward, the snow-clad chain of
the Cordillera separates the Zoological province of Chile, from that of
the wide plains which extend on the other side of the Andes.
The last district which it is at all necessary for me to mention here,
is that of the GALAPAGOS ARCHIPELAGO, situated under the Equator, and
between five and six hundred miles West of the coast of America. These
islands are entirely volcanic in their composition; and on two of them
the volcanic forces have within late years been seen in activity. There
are five principal islands, and several smaller ones: they cover a space
of 2° 10′ in latitude, and 2° 35′ in longitude. The climate, for an
equatorial region, is far from being excessively hot: it is extremely
dry; and although the sky is often clouded, rain seldom falls, excepting
during one short season, and then its quantity is variable. Hence, in
the lower part of these islands, even the more ancient streams of lava
(the recent ones still remaining naked and glossy) are clothed only with
thin and nearly leafless bushes. At an elevation of 1200 feet, and
upwards, the land receives the moisture condensed from the clouds, which
are drifted by the trade wind over this part of the ocean at an
inconsiderable height. In consequence of this, the upper and central
part of each island supports a green and thriving vegetation; but from
some cause, not very easily explained, it is much less frequented, than
the lower and rocky districts are, by the feathered inhabitants of this
archipelago.
By a reference to the localities here described, it is hoped that the
reader will obtain some general idea of the nature of the different
countries inhabited by the several animals, which will be described in
the following sheets.
The vertebrate animals in my collection have been presented to the
following museums:—the Mammalia and Birds to the Zoological Society; the
Fishes to the Cambridge Philosophical Society; and the Reptiles, when
described, will be deposited in the British Museum. For the care and
preservation of all these and other specimens, during the long interval
of time between their arrival in this country and my return, I am deeply
indebted to the kindness of the Rev. Professor Henslow of Cambridge.
With respect to the gentlemen, who have undertaken the several
departments of this publication, I hope they will permit me here to
express the great personal obligation which I feel towards them, and
likewise my admiration at the disinterested zeal which has induced them
thus to bestow their time and talents for the good of Science.