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. 



