When the Europeans came to this continent at the end of the fifteenth century they found it already inhabited by races of men very different from themselves. These people, whom they took to calling 'Indians,' were spread out, though very thinly, from one end of the continent to the other. Who were these nations, and how was their presence to be accounted for? To the first discoverers of America, or rather to the discoverers of the fifteenth and sixteenth centuries (Columbus and his successors), the origin of the Indians presented no difficulty. To them America was supposed to be simply an outlying part of Eastern Asia, which had been known by repute and by tradition for centuries past. Finding, therefore, the tropical islands of the Caribbean sea with a climate and plants and animals such as they imagined those of Asia and the Indian ocean to be, and inhabited by men of dusky colour and strange speech, they naturally thought the place to be part of Asia, or the Indies. The name 'Indians,' given to the aborigines of North America, records for us this historical misunderstanding. But a new view became necessary after Balboa had crossed the isthmus of Panama and looked out upon the endless waters of the Pacific, and after Magellan and his Spanish comrades had sailed round the foot of the continent, and then pressed on across the Pacific to the real Indies. It was now clear that America was a different region from Asia. Even then the old error died hard. Long after the Europeans realized that, at the south, America and Asia were separated by a great sea, they imagined that these continents were joined together at the north. The European ideas of distance and of the form of the globe were still confused and inexact. A party of early explorers in Virginia carried a letter of introduction with them from the King of England to the Khan of Tartary: they expected to find him at the head waters of the Chickahominy. Jacques Cartier, nearly half a century after Columbus, was expecting that the Gulf of St Lawrence would open out into a passage leading to China. But after the discovery of the North Pacific ocean and Bering Strait the idea that America was part of Asia, that the natives were 'Indians' in the old sense, was seen to be absurd. It was clear that America was, in a large sense, an island, an island cut off from every other continent. It then became necessary to find some explanation for the seemingly isolated position of a portion of mankind separated from their fellows by boundless oceans.