With this solution, the difficulty that occurred to Humboldt is in part removed, viz., that the allotted time--one hundred and seventy years--was too short a period in which to transform a tribe of North American Indians into a settled community. The remainder of the difficulty is explained by an event taking place in our own days. It is hardly thirty years since the Apache Indians began the systematic plunder of the northern states of Mexico, and now even these nomades begin to show the first glimmerings of civilization. Their captives teach them the use of much of the plunder they have brought to their own villages. Though their treatment of female captives is inhuman, yet it is not an uncommon thing for a captive to become a wife, and to introduce into her wigwam, and to inculcate upon the minds of her children, a few of the primary ideas of civilization. It is the commonly received notion that the Toltecs abandoned the table-land about the time of the arrival of the Aztecs, but continued to flourish in the region of the Gulf coast and in other parts of the hot country; that the vast ruins which abound in those regions were inhabited cities till within a few generations of the coming of the Spaniards; and that in Yucatan, the part most distant from Mexico, that civilization continued quite down to that period; that for a great portion of the one hundred and seventy years of their national existence, the Aztecs kept up predatory excursions into the Toltec region, and out of its dense population derived an inexhaustible supply of slaves and the plunder of civilization, included in which may have been the best wrought of the stone idols that are still preserved. So that the Aztec civilization resolves itself into the very ancient civilization of the Toltecs. PYRAMID OF PAPANTLA. We have removed to a greater antiquity, but have not got rid of the question of the origin of Mexican civilization. The year 600, named by Humboldt, may be considered as the time of their appearance on the table-land; out many of the ruins in the hot country might claim a thousand years earlier antiquity. These massive remains must have stood, abandoned as they are now, in the midst of the forest, for a long time before the Conquest, as their very existence was unknown to the Spaniards until near the close of the last century. The close resemblance between the apparently most ancient of these works, and those of the Egyptianss and other Eastern civilizations, does not involve the idea of a common origin or of intercourse, but only leads to the suggestion that the human race, in its progress, naturally follows the same path, whether upon the eastern or western continent, and that it is separated by a cycle of thousands of years from the civilization of our day. As a specimen of the works of the Toltecs, I insert a sketch of the pyramid of Papantla. [Illustration: PYRAMID OF PAPANTLA.]