The expedition made by Ehrenberg, Gustav Rose, and myself, by the command of the Emperor of Russia, in 1829, to Northern Asia (in the Ural and Altai mountains, and on the shores of the Caspian Sea), falls between the period of publication of the second and third editions. This expedition has contributed materially to the enlargement of my views in all that regards the form of the surface of the earth, the direction of mountain-chains, the connection of steppes and deserts with each other, and the geographical distribution of plants in relation to ascertained conditions of temperature. The long subsisting want of any accurate knowledge on the subject of the great snow-covered mountain-chains which are situated between the Altai and the Himalaya (_i. e._ the Thian-schan and the Kuen-lün), and the ill-judged neglect of Chinese authorities, have thrown great obscurity around the geography of Central Asia, and have allowed imagination to be substituted for the results of observation in works which have obtained extensive circulation. In the course of the last few months the hypsometrical comparison of the culminating summits of the two continents has almost unexpectedly received important corrections and additions, of which I hasten to avail myself. (Vol. i. pp. 57-58, and 92-93.) The determinations of the heights of two mountains in the eastern chain of the Andes of Bolivia, the Sorata and the Illimani, have been freed from the errors which had placed those mountains above the Chimborazo, but without as yet altogether restoring to the latter with certainty its ancient pre-eminence among the snowy summits of the New World. In the Himalaya the recently executed trigonometrical measurement of the Kinchinjinga (28178 English feet) places it next in altitude to the Dhawalagiri, a new and more exact trigonometrical measurement of which has also been recently made. For the sake of uniformity with the two previous editions of the “Ansichten der Natur,” I have given the degrees of temperature in the present work (unless where expressly stated otherwise) in degrees of Reaumur’s scale. The linear measures are the old French, in which the toise equals six Parisian feet. The miles are geographical, fifteen to a degree of the equator. The longitudes are reckoned from the Observatory at Paris as a first meridian. BERLIN, 1849. NOTE BY THE TRANSLATOR.