72 ON THE GEOGRAPHY OF ANIMALS. 



(103.) The zoology of Mexico conducts us at once 

 into the third great division of the American province, 

 of whose zoological features we shall now proceed to 

 give a rapid sketch. It must first be premised that 

 the equinoctial provinces, forming the modern republics 

 of Guatemala and Colombia, have never been fully 

 explored by modern naturalists ; that, notwithstanding 

 the celebrated Humboldt traversed the whole of Chili 

 and Peru, his other pursuits left him little or no time to 

 collect or to investigate their animal productions ; and 

 that many other parts of this vast and fertile continent 

 have hitherto been but superficially examined. Our ma- 

 terials, therefore, must be ch'eflydrawnfrom the immense 

 collections that have been made of late years in different 

 parts of Brazil ; from our own personal researches in 

 that vast empire; and from a few other authentic 

 sources. We have before remarked, that both animals 

 and vegetables rapidly increase in number and variety, 

 the nearer we approach the equinoctial line, where the 

 humidity of the atmosphere is more remarkable, to com- 

 mon observers, than any extraordinary degree of heat. 

 That the former is more essential to this fecundity than 

 the latter, is perfectly manifest, upon looking to the 

 deserts of Africa, situated under similar degrees of 

 latitude. But the variety of animals in tropical 

 America is so much greater than in any other part 

 of the world, that we naturally enquire what are 

 the causes generally assigned for this excessive exu- 

 berance? This question has been so well replied to 

 by a celebrated traveller, that we shall here insert his 

 observations, 



(104.) The causes of the general fertility of Ame- 

 rica, and more particularly of the southern division, 

 assigned by M. Humboldt, are these : — " The narrow- 

 ness of this variously indented continent; its great 

 extension towards the icy pole : the wide ocean over 

 which the tropical winds blow ; the flatness of the 

 eastern coasts ; the currents of cold sea- water which 

 flow northwards from the Terra del Fuego towards 



