| OCR Text |
Show 4.'.' •'*•' BASIS OP AMERICAN HISTORY [ 1500 • * * 1 ;\* migration and the consequent contact of differing "••" groups, also affects development of culture even among primitive peoples whose institutions tend to evolve along independent lines. Hence the political fortimes even of a people of high culture are largely dependent upon the physical geography of their home. A comprehensive history of the American nation must, therefore, be based upon an accurate appreciation of the features of the territory within which it is working out its future; and the physical geography of the United States demands consideration not only of that portion embraced within the present political boundariS7 but also of the general characteristics of the continent of North America as a whole. 1 J The great triangle of North America presents its base to the arctic and narrows to its apex in tike tropics. This means that its greater area is includild in high latitudes and ruled by a relatively sever* inmate. While the United States lies mainly in the southern half, roughly between the parallels pi 290 N. and 490 N., its greatest extent lies far enough north to gain the advantage which colder clima tes seem to possess in producing efficient racial groufis. The character of the / coast - line of a continent is a matter of prime concern in colonization or invasion, and becomes of constantly greater iin 1 For general authorities on the physiography of the United States, see chap, xviii., below. 1 1 \ |
