At the western end of Tibet the Tso-mo-gualari, a series of five connected lakes, lies at an elevation of 14,000 feet in a narrow valley winding for over 100 miles from east to west, among magnificent snowy mountains. The upper lakes, which drain from one to the other and are fresh, lie in Tibetan territory and are but imperfectly known; the lowest and largest lake, Pangong, which has no outlet and is saline, lies in the Indian province of Ladakh or Little Tibet, and is visited almost yearly by British sportsmen. As the two main lakes, Pangong and Nyak Tso, with a combined length of 75 miles, and apparently the others also, lie at nearly the same level and are separated from one another only by an alluvial fan or delta like that at Interlaken in Switzerland, the whole series may be regarded as occupying a single basin with a length of 105 miles, a maximum width of 4 miles, and an average width of only 1.8 miles where covered with water. The basin appears to be due to glacial erosion, and the lakes, as their scenery indicates, belong to the same type as the famous valley lakes of Switzerland. Old moraines show that previous to the formation of the present lake the basin was once or twice filled with ice; while lacustrine deposits and elevated beaches show that in later times the lake-level has fluctuated in response to changes of climate less severe than those which caused the invasion of the basin by glaciers. Thus a record of various phases of the glacial period is preserved in a region where it is especially valuable for purposes of comparison. While on the way to Chinese Turkestan as a member of the Barrett Expedition to central Asia, I visited Pangong, remaining there from May 1 to May 6, 1905. The lake is exquisitely beautiful, a sparkling sheet of the clearest, deepest blue, shading delicately to purple in the shadows and to pure, pearly green in the shallow rim