The country is dry, rolling, and unproductive. In some places there is a sparse growth of cacti and thorny shrubbery, but vast areas are rocky and barren of all vegetation. We crossed ridge after ridge, the elevation of the trail varying between eight thousand and twelve thousand feet. Travel in this type of country is most trying. Water is so scarce that long distances must be covered in order to find suitable camping-sites; in one instance we were compelled to ride thirty-six miles in the course of a day, between streams. The temperature varies 100° each twenty-four hours. At two in the afternoon the thermometer registered 132° F.; at night ice formed on the water in our pails. Christmas day was spent at Puno, with every member of the party ill from the effects of the climatical changes. The inhabitants went about their occupations as usual, quite ignoring this all-important opportunity for a _fiesta_. All the dwellings of the Indians were made of adobe. In the walls of some of them rows of disused earthenware pots had been used as building material. When the huts crumbled, a fine collection of pottery was covered up in the mound. This is probably an ancient custom and may account for much of the material found in old ruins to-day. Two days later, the last of the long, weary miles across the cheerless upland had been left behind, and at noon we galloped briskly into Villazón, on the Bolivian side of the border. Villazón contains about a score of scattered, low, adobe buildings. We arrived on a Sunday, when the customhouse was closed, but the officials in charge very courteously permitted us to proceed on our way. A brook three or four feet wide separates the two republics and, stepping across this, we found ourselves in La Quiaca and--in Argentina. CHAPTER XXIII BIRD-NESTING IN NORTHWESTERN ARGENTINA La Quiaca is similar in size and appearance to Villazón. There are a number of stores or trading-posts where miners from the surrounding mountains secure their outfits and provisions. It is also the terminus of the railroad from the south. One may go by rail directly to Buenos Aires. The settlement stands on a level, wind-swept plateau, and the weather was very cold. The neighboring peaks of the Andes are rich in mines, and multitudes of llamas and mules come down the steep trails each day, laden with copper, bismuth, silver ore, and gold ore. They discharge their burdens at the railroad-station, where it is loaded on cars to be hauled to the smelters in Buenos Aires. Our object in coming to the Argentine was to continue the biological survey we had carried on in Bolivia; and also to secure specimens of a rare little bird (_Scytalopus_) which was thought to exist in the province of Salta. The acquisition of this bird was most important for the light it would throw on certain problems of distribution.