[Sidenote: Agriculture carried to perfection.] In their extraordinary provisions for agriculture, the national pursuit, the skill of the Peruvians is well seen. A rapid elevation from the sea-level to the heights of the mountains gave them, in a small compass, every variety of climate, and they availed themselves of it. They terraced the mountain sides, filling the terraces with rich earth. They excavated pits in the sand, surrounded them with adobe walls, and filled them with manured soil. On the low level they cultivated bananas and cassava; on the terraces above, maize and quinoa; still higher, tobacco; and above that the potato. From a comparatively limited surface, they raised great crops by judiciously using manures, employing for that purpose fish, and especially guano. Their example has led to the use of the latter substance for a like purpose in our own times in Europe. The whole civilized world has followed them in the cultivation of the potato. The Peruvian bark is one of the most invaluable remedies. Large tracts of North America would be almost uninhabitable without the use of its active alkaloid quinine, which actually, in no insignificant manner, reduces the percentage mortality throughout the United States. [Sidenote: The great aqueduct of Condesuya.] Indispensably necessary to their agricultural system were their great water-works. In Spain there was nothing worthy of being compared with them. The aqueduct of Condesuya was nearly 500 miles long. Its engineers had overcome difficulties in a manner that might well strike modern times with admiration. Its water was distributed as prescribed by law; there were officers to see to its proper use. From these great water-works and from their roads it may be judged that the architectural skill of the Peruvians was far from insignificant. They constructed edifices of porphyry, granite, brick; but their buildings were for the most part low, and suitable to an earthquake country.