have been most neglected by explorers. Several travellers have touched Tibet on the north-east and on the west, and through the journeys of the Indian pundits we have long had a fairly clear conception of southern Tibet, at all events of certain portions of it. But the parts of the high, inaccessible Tibet which I made it my object to explore, namely the region bounded by the Kwen-lun on the north, the central lacustrine area on the south, the Kara-korum route on the west and long. 91° E. Greenwich on the east, has been visited only by Nain Singh, Krishna, Prschevalskij, Carey, Pjevtsoff, Bonvalot, Littledale, Rockhill, Dutreuil de Rhins, Wellby, Bower, Deasy, and Rawling, and to these must be added certain journeys in the peripheral parts, e. g. the Kara-korum route, which has been traversed many times, and the districts around the Panggong-tso. Yet some of the travellers whom I have just enumerated have only in part touched the region thus defined. Really extensive journeys on the Central Tibetan highlands have been carried out only by Nain Singh, Krishna, Bonvalot and Orléans, Dutreuil de Rhins and Grenard, Bower, Wellby and Malcolm, Deasy, Littledale, and myself. It is in the material which these explorers have brought home with them. that we can alone hope to find points of contact with my journeys. But the journeys of such important travellers as Count Széchenyi, Roborovskij, Holderer and Futterer, Kosloff, Bonin, Filchner and Tafel, and several others lie entirely outside my purview. In his Versuch einer Orograj5hie des Kwenlun Dr. Georg Wegener has published an excellent map of all the journeys in Tibet which have touched the Kwen-lun Mountains and which date from before 1891. But it does not of course embody the journeys which have been carried out during the last fifteen years, journeys which are calculated in an especial manner to throw light upon the orographical structure of the Kwen-lun and the character of the highlands of Central Tibet.
But let us proceed to examine the journeys which possess interest for us, and which can furnish us with the requisite material for a comparison. I will begin with Prschevalskij's first, and perhaps his most remarkable, journey in Central Asia, in the years 1870-73, by quoting a couple of extracts which have to do with Northern Tibet. Although that part of his journey lies really outside the region I have defined, still the following passages will justify my quoting them in this connection.
Prschevalskij first penetrated Tibet from the Koko-nor and Tsajdam. The observations which he then made, in so far as they are of general geographical interest, are reproduced in the following greatly condensed account: »Between the lake of Toso-nor (Tosun-nor) in the east and the river of Nomochun-gol in the west stretches the mountain-range of Burchan-Budha, bordering the high plateau of Tibet on the north. In the course of 3o versts this range gradually rises to an altitude of about 466o m. and on its southern side sinks slowly down towards the valley of Nomochun. It is only near the crest that the ascent is steep; yet notwithstanding the considerable altitude, the summit bears no perpetual snow and it is only in the east that it touches the snow-line. When we visited the same region in November we found a mere sprinkling on the northern versant only; •but when we returned that same way in February we failed to perceive any trace of snow, even in the glens. The Burchan-Budha range forms a natural boundary between Tsajdam and
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