coast. For centuries this has laid upon both man and beast the heavy necessity of making such use of natural resources as they could. There were high mountains to cross, difficult streams to ford; at some seasons of the year there was drought so severe that water for stock was hard to find, at others the streams were in flood; and the extremes of weather encoun- tered—the hailstorms and occasional snowstorms of the cordil- lera, the dust storms and burning salars of the high basins—all required the hardiest types of animals. The mule is not only well adapted to this service but is economical in that it has learned to forage at night for its food. It may be driven across the most inhospitable country in South America, brows- ing only on dried grass and bushes and perhaps a little green stuff carried with the cargo and some dried corn or preferably barley. It will live and work under these circumstances where a horse would die. Only the llama, the native beast of burden, can be compared to it for hardiness, and the llama is unable to carry heavy loads or to cover distances rapidly. After a severe journey the mule is rested and well fed for such time as it requires to regain its strength and to be in condition to undertake the next journey.
The source of the mule supply for the plateau was the Plata region. Between the two there was, on the one hand, a broken mountain country in places thinly inhabited, in places cold and barren; and, on the other, wide arid pampas, where good cattle pasture was found only at places widely separated and attained by crossing rivers, sometimes in flood, sometimes entirely dry. The times and the seasons of rain were reflected in a periodic traffic, and this naturally led to the development of the live-stock fairs at selected points, where buyer and seller could meet and conduct their business in short order and re- turn home again.
The journey from Buenos Aires to Peru was accomplished in three stages, the first to Cérdoba, where in the rainy season (November to March) water and pasture were to be had in abundance. There the troops were pastured for some months. In April they set out on the second stage of their journey. They were organized into troops of 1300 or 1400 head in charge
