214 THE PHILOSOPHY OF BIRDS’ NESTS. 
great height, with an open bamboo floor; and the 
whole structure is exceedingly slight and thin. Now, 
what can be the reason of this remarkable difference 
between countries, many parts of which are strikingly 
similar in physical conditions, natural productions, and 
the state of civilization of their inhabitants? We ap- 
pear to have some clue to it in the supposed origin 
and migrations of their respective populations. The 
indigenes of tropical America are believed to have im- 
migrated from the north—from a country where the 
winters are severe, and raised houses with open floors 
would be hardly habitable. They moved southwards 
by land along the mountain ranges and uplands, and 
in an altered climate continued the mode of construc- 
tion of their forefathers, modified only by the: new 
materials they met with. By minute observations of 
the Indians of the Amazon Valley, Mr. Bates arrived 
at the conclusion that they were comparatively recent 
immigrants from a colder climate. He says :—‘ No 
one could live long among the Indians of the Upper 
Amazon without being struck with their constitutional 
dislike to the heat. . . Their skin is hot to the touch, 
and they perspire little. . . They are restless and 
discontented in hot, dry weather, but cheerful on cool 
days, when the rain is pouring down their naked 
backs.” And, after giving many other details, he 
concludes, “‘ How different all this is with the Negro, 
the true child of tropical climes! The impression gra- 
dually forced itself on my mind that the Red Indian 
lives as an immigrant or stranger in these hot regions, 
