It was frequently the policy of the Incas, after providing a deserted tract with the means for irrigation, and thus fitting it for the labors of the husbandman, to transplant there a colony of mitimaes, who brought it under cultivation by raising the crops best suited to the soil. While the peculiar character and capacity of the lands were thus consulted, a means of exchange of the different products was afforded to the neighboring provinces, which, from the formation of the country, varied much more than usual within the same limits. To facilitate these agricultural exchanges, fairs were instituted, which took place three times a month in some of the most populous places, where, as money was unknown, a rude kind of commerce was kept up by the barter of their respective products. These fairs afforded so many holidays for the relaxation of the industrious laborer.26 Such were the expedients adopted by the Incas for the improvement of their territory; and, although imperfect, they must be allowed to show an acquaintance with the principles of agricultural science, that gives them some claim to the rank of a civilized people. Under their patient and discriminating culture, every inch of good soil was tasked to its greatest power of production; while the most-unpromising spots were compelled to contribute something to the subsistence of the people. Everywhere the land teemed with evidence of agricultural wealth, from the smiling valleys along the coast to the terraced steeps of the sierra, which, rising into pyramids of verdure, glowed with all the splendors of tropical vegetation. The formation of the country was particularly favorable, as already remarked, to an infinite variety of products, not so much from its extent as from its various elevations, which, more remarkable, even, than those in Mexico, comprehend every degree of latitude from the equator to the polar regions. Yet, though the temperature changes in this region with the degree of elevation, it remains nearly the same in the same spots throughout the year; and the inhabitant feels none of those grateful vicissitudes of season which belong to the temperate latitudes of the globe. Thus, while the summer lies in full power on the burning regions of the palm and the cocoa-tree that fringe the borders of the ocean, the broad surface of the table-land blooms with the freshness of perpetual spring, and the higher summits of the Cordilleras are white with everlasting winter.