The prosperity of the town was also shown by corrugated iron roofs. Far less picturesque than thatch or tile, they require less attention and give greater satisfaction during the rainy season. They can also be securely bolted to the rafters. On this wind-swept plateau we frequently noticed that a thatched roof was held in place by ropes passed over the house and weights resting on the roof. Sometimes to the peak of a gable are fastened crosses, tiny flags, or the skulls of animals--probably to avert the Evil Eye or bring good luck. Horseshoes do not seem to be in demand. Horses' skulls, however, are deemed very efficacious. On the rim of the Titicaca Basin is La Raya. The watershed is so level that it is almost impossible to say whether any particular raindrop will eventually find itself in Lake Titicaca or in the Atlantic Ocean. The water from a spring near the railroad station of Araranca flows definitely to the north. This spring may be said to be one of the sources of the Urubamba River, an important affluent of the Ucayali and also of the Amazon, but I never have heard it referred to as "the source of the Amazon" except by an adventurous lecturer, Captain Blank, whose moving picture entertainment bore the alluring title, "From the Source to the Mouth of the Amazon." As most of his pictures of wild animals "in the jungle" looked as though they were taken in the zoölogical gardens at Para, and the exciting tragedies of his canoe trip were actually staged near a friendly hacienda at Santa Ana, less than a week's journey from Cuzco, it is perhaps unnecessary to censure him for giving this particular little spring such a pretentious title. The Urubamba River is known by various names to the people who live on its banks. The upper portion is sometimes spoken of as the Vilcanota, a term which applies to a lake as well as to the snow-covered peaks of the cordillera in this vicinity. The lower portion was called by the Incas the Uilca or the Uilcamayu.