A plateau of considerable but very unequal elevation runs with little interruption, in a S.S.W.-N.N.E. direction, from Eastern Thibet towards the mountain node of Kentei, south of Lake Baikal, and is known by the names of Gobi, Scha-mo, (sand desert,) Scha-ho. (sand river,) and Han-hai. This swelling of the ground, which is probably more ancient than the elevation of the mountain-chains by which it is intersected, is situated, as we have already remarked, between 81° and 118° east longitude from Greenwich. Measured at right angles to its longitudinal axis, its breadth in the south, between Ladak, Gertop, and H’lassa (the seat of the great Lama), is 720 miles; between Hami in the Celestial Mountains, and the great curve of the Hoang-ho, near the In-schan chain, it is scarcely 480; but in the north, between the Khanggai, where the great city of Karakhorum once stood, and the chain of Khin-gan-Petscha, which runs in a meridian line (in the part of Gobi traversed in going from Kiachta to Pekin by way of Urga), it is 760 miles. The whole extent of this elevated ground, which must be carefully distinguished from the more eastern and higher mountain-range, may be approximately estimated, including its deflections, at about three times the area of France. The map of the mountain-ranges and volcanoes of Central Asia, which I constructed in 1839, but did not publish until 1843, shows in the clearest manner the hypsometric relations between the mountain-ranges and the Gobi plateau. It was founded on the critical employment of all the astronomical determinations accessible to me, and on many of the very rich and copious orographic descriptions in which Chinese literature abounds, and which were examined at my request by Klaproth and Stanislaus Julien. My map marks in prominent characters the mean direction and the height of the mountain-chains, together with the chief features of the interior of the continent of Asia from 30 to 60 degrees of latitude, between the meridians of Pekin and Cherson. It differs essentially from any map hitherto published.