PHYSICAL GEOGRAPHY. 



son, the passenger pigeons forming themselves into vast flocks for the journey, one of 

 which has been calculated to include 2,230,000,000 individuals. We are familiar with 

 the cuckoo as our visitor in spring, and Avith the house-swallow as our guest through the 

 summer, the latter usually departing in October to the warmer regions of the south, 

 wintering in Africa, returning again when a more genial season revives its insect food. 

 By cutting off tAvo claws from the feet of a certain number of swallows, Dr. Jenner as 

 certained the fact, of the same individuals reappearing in their old haunts in the follow 

 ing year, and one was met with even after the lapse of seven years. The arctic birds 

 migrate farther south, when the seas, lakes, and rivers, become covered with unbroken 

 sheets of ice ; the swans, geese, ducks, divers, and coots flying off in regular phalanxes to 

 regions where a less rigorous winter allows of access to the means of life. Hence, soon 

 after we lose the swallows, we gain the snipes and other waders, which have fled from 

 the hard frozen north to our partially frozen morasses, where their ordinary nutriment 

 may still be obtained. The equinoctial zone, where the seasonal change is that of 

 humidity and drought, furnishes an example of the same phenomenon. As soon as the 

 Orinoco is swollen by the rains, overflows its banks, and inundates the country on either 

 side, an innumerable quantity of aquatics leave its course for the West India islands on 

 the north, and the valley of the Amazon on the south, the increased depth of the river, 

 and the flooded state of the shores, depriving them of the usual supply of fish and insects. 

 Upon the stream decreasing, and retiring within its bed, the birds return. 



The class of Quadrupeds brings us to the most perfectly organised members of the 

 animal kingdom, as well as to the largest, most powerful, and ferocious ; of which the lion, 

 tiger, elephant, rhinoceros, hippopotamus, panther, leopard, hyaena, bear, and giraffe are 

 familiar examples. The weight of some of these animals, which may be taken as an 

 indication of their comparative size, has been computed to be a ton for the giraffe, three 

 tons for the rhinoceros, three tons and a half for a hippopotamus sent to England cut up 

 into pieces, while the elephant that was killed at Exeter Change was estimated to weigh 

 five tons and a half. The class embraces a number of animals remarkable for their 

 beauty, as the striped zebra and the bounding antelope, particularly the gazelle species, 

 whose light forms, brilliant and expressive eyes, have from remote antiquity been the 

 favourite themes of eastern song. It includes also various quadrupeds, readily capable of 

 domestication, which largely minister to the welfare of the human race, as the horse, ox, 

 camel, and deer. In examining the distribution of the wild quadrupeds, the hot regions, 

 extending from the equator to a few degrees beyond the tropics, are found to yield the 

 greatest number of tribes and individuals, as well as of those animals which are dis 

 tinguished by their bulk, strength, and ferocity. It has been commonly assumed, but 

 without sufficient authority, that we have here, an excessive development of animal life, as 

 an instance of intentional adjustment to a luxuriant vegetation. Thus Mr. Prout remarks, 

 in his Bridgewater Treatise, that "in tropical climates, the qualities of animals, as well 

 as those of vegetables, are developed to the utmost ; and hence arises that harmonious 

 adaptation of all the works of nature, conspicuous indeed in all climates, but in tropical 

 climates more especially: for where else than amidst the profuse exuberance of the 

 vegetation within the tropics could the elephant, the rhinoceros, the giraffe, and other 

 large quadrupeds find subsistence ? "Where else could we expect to see such birds as the 

 ostrich and the cassowary such reptiles as the crocodile such serpents as the boa ?" It 

 need only be remarked, to show the fallacy of this statement, that, upon the principle laid 

 down, intertropical America ought to be well stocked with the animal tribes of the 

 largest class, whereas it is remarkably deficient in them ; while in Africa the same tribes 

 should be rare, whereas that is precisely the region where they are most abundant. 



The incorrectness of the opinion advanced by Mr. Prout, in common with other 



