IV 
ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 
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 Penin- 
sula 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, Copiapo, 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 
