Tampu Machai is located on a little bluff above the Lkalla Chaca, a small stream which finally joins the Huatanay near the town of San Sebastian. Before it reaches the Huatanay, the Lkalla Chaca joins the Cachimayo, famous as being so highly impregnated with salt as to have caused the rise of extensive salt works. In fact, the Pizarros named the place Las Salinas, or "the Salt Pits," on account of the salt pans with which, by a careful system of terracing, the natives had filled the Cachimayo Valley. Prescott describes the great battle which took place here on April 26, 1539, between the forces of Pizarro and Almagro, the two leaders who had united for the original conquest of Peru, but quarreled over the division of the territory. Near the salt pans are many Inca walls and the ruins of structures, with niches, called Rumihuasi, or "Stone House." The presence of salt in many of the springs of the Huatanay Valley was a great source of annoyance to our topographic engineers, who were frequently obliged to camp in districts where the only water available was so saline as to spoil it for drinking purposes and ruin the tea. The Cuzco Basin was undoubtedly once the site of a lake, "an ancient water-body whose surface," says Professor Gregory, "lay well above the present site of San Sebastian and San Geronimo." This lake is believed to have reached its maximum expansion in early Pleistocene times. Its rich silts, so well adapted for raising maize, habas beans, and quinoa, have always attracted farmers and are still intensively cultivated. It has been named "Lake Morkill" in honor of that loyal friend of scientific research in Peru, William L. Morkill, Esq., without whose untiring aid we could never have brought our Peruvian explorations as far along as we did. In pre-glacial times Lake Morkill fluctuated in volume. From time to time parts of the shore were exposed long enough to enable plants to send their roots into the fine materials and the sun to bake and crack the muds. Mastodons grazed on its banks. "Lake Morkill probably existed during all or nearly all of the glacial epoch." Its drainage was finally accomplished by the Huatanay cutting down the sandstone hills, near Saylla, and developing the Angostura gorge. In the banks of the Huatanay, a short distance below the city of Cuzco, the stratified beds of the vanished Lake Morkill to-day contain many fossil shells. Above these are gravels brought down by the floods and landslides of more modern times, in which may be found potsherds and bones. One of the chief affluents of the Huatanay is the Chunchullumayo, which cuts off the southernmost third of Cuzco from the center of the city. Its banks are terraced and are still used for gardens and food crops. Here the hospitable Canadian missionaries have their pleasant station, a veritable oasis of Anglo-Saxon cleanliness.