(v4 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 chiefly drawn from 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. a 
(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 
