Continuing our voyage along the coast, the eye may fall upon the white guano-covered headlands, and the attention is suddenly arrested by what appears at first sight to be a low dark cloud moving on the face of the waters. It approaches, and we see that it is not a cloud, but a flight of birds, innumerable, and flying in close formation--at times, indeed, they obscure the sky. These are the guano-producing birds, which haunt the rocky headlands and islets, and whose product has been so considerable a source of wealth and contention on this coast. Guano was used by the Incas in their intelligent and painstaking agricultural operations, and its misuse or monopoly was prohibited. The Incas, vestiges of whose remarkable structures and curious customs we find scattered in profusion throughout the enormous territory--perhaps two thousand miles in length--which formed their empire, upon whose coast we are journeying here, made little use of the sea, except for fishing. By relays of posts, of Indian runners, fish was carried in fresh, across the deserts and over the Cordillera, for the table of the Inca at Cuzco, which town, the ancient Mecca and capital of the early Peruvians, is situated in a valley 11,500 feet above sea-level and over two hundred miles inland--a remarkable performance. The Incas were not a seafaring people, and their civilization--for it fully merits the name of such--was indeed cut off from the rest of the world both by the ocean and by the enormous rugged chains of the Andes, and by the impenetrable forests of the Amazon basin on the east. As far as is known, they appear not to have had knowledge even of the contemporaneous cultures of the Mayas, the Aztecs, and the Toltecs of Mexico and Central America, although all these early American cultures may have had a common origin, in times much nearer the general childhood of the world. Was this coast first explored and even settled by the Chinese long before Columbus sailed? There are reasons for thinking this may have been so. The exploits of Pizarro and his followers took place in the neighbourhood of Tumbez, near the westernmost point of the South American Continent. How, fighting against famine, they made their way along this stark and inhospitable littoral and ascended the Andes, where by a combination of intrepidity and treachery they overcame the reigning Inca chief and his people, forms one of the most fascinating episodes of early American history.