of the Gulf of Mexico. The last civilization was in the course of radiation and transformation when the Europeans came to America, and was wholly independent and autonomous; but, weak and relatively new, it was not able to resist the sudden onset of a stronger race.
Toward the center of the space whose extremes we have marked out must be placed two other centers of civilization, more ancient than either of the two already named, and in the same zone of latitude—Egypt, in the valley of the Nile, and near the Arabian Gulf, and Mesopotamia, near the head of the Persian Gulf. Thus, each continental mass had its particular center of civilization, except Asia, which had two—one in the extreme east, the other near the line which joins it to Europe. This peculiar grouping of the chief centers of civilization in such a relation of neighborhood constitutes the most considerable palæoethnic fact that we are able to record. The Nile and the Syrian sea on the west, upper Armenia and the Caspian on the north, the Hindoo-Koosh and the Indus on the east, and the Arabian Sea on the south, bound the region where Cushites, Semites, and Aryans, the first farmers, workers, and founders of cities, the second pastoral people, and the third mountaineers, afterward emigrants and conquerors, met, elbowed each other, and mingled, conquerors and conquered by turns, inventing arts and the use of metals, learning arms and how to organize themselves hierarchically, reaching their ideal through religion, and having in writing the most powerful instrument at the disposition of human intelligence. With them we have the beginning of history, and a continuous chain of social organizations, down to our own days. The growth of civilization in these centers leaves, however, still unaccounted for the diffusion of mankind all over the earth, which took place at a period far anterior to it.
The spread of man throughout Europe and Asia does not offer very great difficulties, for, in consequence of the long distance for which the two continents are joined, Europe is in reality only a dependency of Asia; and occupation of Europe from Asia is conformable to religious traditions. The difficulties are, however, formidable when we come to America, which we find occupied from one end to the other by races whose unity has struck the best observers. Not only, moreover, did the American man inaugurate on the soil of the New World an original and relatively advanced civilization, but he has left, chiefly in the north, indisputable traces of his presence in the most remote ages. Palæolithic implements have been found in the valley of the Delaware, at Trenton, New Jersey, and near Guanajuato in Mexico, so clearly characterized that they can not be mistaken, the situation of which at the base of the Quaternary alluvions and their coexistence with elephants and mastodons, indicate the existence of a race contemporaneous with that of the gravels of the Somme, having the same industry and doubtless the same manners and physical traits. Whence could this primitive American race, sister to the one that lived