THE work of the great N. M. Prjevalsky, the first explorer of Central Asia, has been continued by one of his pupils and lieutenants, Mr. P. K. Kosloff, whose portrait appears as frontispiece to vol. i. of the account of the expedition conducted by himself in 1899–1901 to Mongolia and Cham. This volume is dedicated to the memory of the great pioneer, who projected a fifth journey which he did not live to accomplish. As a member of former expeditions, Mr. Kosloff was well equipped for the vast undertaking which he describes. At the end of 1898 he submitted a plan for exploration of the southern or Mongolian Altai, the neighbouring central Gobi, and, if practicable, of eastern and central Tibet. The Imperial Russian Geographical Society and the Ministry of War warmly approved, invested Mr. Kosloff with powers of command and discretion, and furnished the expedition with scientific instruments. Under distinguished auspices the party made its way to the Altai station, and halted to survey the sublime snow-clad range and to collect specimens. Here the members met with a venerable member of a company of Old Believers, Rachmanoff, whose pilgrimages and adventures of mçre than forty years are mentioned by Prjevalsky. Having achieved satisfactory results, the expedition moved into the arid, sandy wastes of Gobi, an unattractive region. It met with a hearty welcome at the Tshortentan monastery from the lamas, whose personalities and the etiquette of their rule are described at length. Next the party proceeded to the salt-marsh district of Tsaidam. The Mongols of this region appear to have had a distinguished history, but in course of time were forced to cede territory to Chinese and Tibetans, their conquerors coitipelling them to destroy all documents and records of the earlier Mongol princes. There is only local tradition to depend upon, without any means of verification. A chapter is devoted to an ethnographical sketch of the Tsaidam Mongols, and in other chapters the author discusses Mongolian marriage customs and folklore. A wallet of excellent maps, showing the routes taken by Prjevalsky and other explorers, is appended to the volume.