TEE HUMAN SPECIES. 457 



Topographic and climatic differences led, however, to lines of 

 minor ethnic variation, which, for environmental reasons, cross each 

 other at right angles. Topographically considered, the western hemi- 

 sphere combines longitudinal uniformity with latitudinal diversity, so 

 that in this respect the two sections of the continent are very much 

 alike. Both North and South America have their mountain ranges 

 along the west and the mural masses of each section are succeeded by 

 deforested plains and forested river valleys extending to the Atlantic 

 coast. As a result, there is a corresponding variation of ethnic types 

 running through both continents from west to east, showing more or 

 less marked distinctions between the men of the mountain, the men 

 of the plain, the men of the forest and the men of the shore. Owing to 

 its extension across almost all the degrees of latitude, the western hemi- 

 sphere offers, on the other hand, an extreme longitudinal range of cli- 

 mate, so that in this respect there is a striking difference between the 

 two Americas. Both triangular sections have their bases on the north 

 and their apexes turned towards the south in such a way that the 

 northern continent is mostly temperate and the southern continent 

 predominantly tropical. As a result, there are likewise lines of ethnic 

 variation running along the longitudes, which distinguish the inhabit- 

 ants of the northern or temperate continent from the inhabitants of 

 the southern or tropical continent. From the fact that they cross each 

 other at right angles, however, these longitudinal and latitudinal 

 variations tend to neutralize each other to a large extent and leave a 

 relatively uniform type. It is possible on this account, despite the 

 diversity that exists among the American aborigines, to distinguish 

 the Eed man from his human fellows by his brown or copper-colored 

 skin; his lank black hair, which is nearly round in cross section; his 

 deep-set beady black eyes; his aquiline nose; his massive jaws; and his 

 finely formed figure. 



There has been no attempt in the foregoing, either to make an exact 

 analysis of the ethnic make-up of mankind, or to follow the process of 

 varietal differentiation in detail. The sole purpose of the enquiry has 

 been, by combining the analytical and geographical methods of investi- 

 gation, to indicate the probable order of racial ramification and to 

 determine in a general way under what environmental conditions the 

 ethnic differentiation of mankind occurred. 



