GEOGRAPHICAL INTRODUCTION. 
v 
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. Pro- 
fessor Henslow of Cambridge. With respect to the gentlemen, who have under- 
taken 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. 
