According to the mean measurements of Humboldt, the lower plateau of Auvergne, in southern France, is 1040 feet in elevation; still less in altitude (840 feet) is the plateau of Burgundy and Lothringia, between the Vosges and the Ardennes. Limousin, Aveyron, la Forez, Monts, and Côte d’Or are plateaus.
The plateau of Lothringia, whose mean elevation is 648 feet, lies between the Rhine and the Moselle. The plateau of Luxemburg extends northward to the Eifel, where Prum lies, and to the Ardennes, where Malmedy, Eupen, Namur, Liege, and Aix-la-Chapelle lie.
In Middle Germany, a series of plateaus of the second grade begins in Upper Hesse, and extends eastward, crossed by mountains and valleys, traversing Upper Silesia and Galicia, and running along the northern side of the Carpathian Mountains to Podolia, on the Dnieper, thus embracing a strip extending through the larger part of central Europe.
A line of plateaus begins still farther to the north, at the low hills of Jutland, crossing Holstein, Mecklenberg, the whole southern edge of Pomerania, and extending to Lithuania and the Valdai Hills. It is characterized by a band of inland lakes, whose basins it incloses, and is crossed by the valleys of the Oder, Vistula, Niemen, and Duna. It has been called the Pomerania lake country. In the hollows where the lakes lie, (whose surfaces are, at the highest, not more than 300 feet above the sea,) and yet more in the depressions, where rivers break through, the level descends to as low a point as that of the great plain of Central Europe; but at other places it rises to an elevation as high as 500 feet, and so touches upon the limits of plateaus of the second range. Many parts of this broad upland may possibly be formed of shifting sand dunes which have been gradually piled up along the sea line. The plateau reaches its highest point at the eastern end, in the Valdai Hills, where it averages 1000 feet in elevation. The highest point is 1100 feet. East of the Volga, which rises at the eastern side of these hills, the plateau falls off by imperceptible steps, till it is lost in the great Russian plain.
In the peninsulas of Southern Europe, as in the Morea, (2000 feet,) and in the Crimea, (800 to 1200 feet,) the plateau again appears in not insignificant proportions.
The lower range of plateaus, it will be seen, is far more frequently met with through all parts of the earth than the higher, yet both combined occupy a larger share of the surface of the globe. We can designate them as sharply defined and broadly massive elevations, in contradistinction to the long, narrow, and broken masses which have received the name of mountain chains. The latter have too often been confounded with the former and have received from geographers a treatment disproportionately full in relation to their claims. The plateau has been until recently an almost forgotten geographical element. Humboldt restored it to its rightful place; by many hundreds of measurements he has accurately settled its form, its effect on climate, on isothermal lines, on agriculture, on the physical and moral life of nations, and even on the course of human history.
In closing this attempt at a general consideration of plateaus, I must confirm the reproach which Humboldt has cast upon most geographers of this day for their abuse of the word plateau. And I must at the same time admit that it is justly due to some parts of my own “Erdkunde,” where I have considered the plateau systems of Central Asia and Africa. When I wrote the pages of that work, thirty and more years ago, there were no scientific measurements then made of those regions, and the general ignorance led to a premature generalization, in which I used the ascertained features of the New World as probably in analogy with the unexplored center of the Old World. This use of really untrue analogies was carried by others to great lengths, and choratographers went so far as to depict the country according to the hypothesis of those who had written at first hand, and after using all the lights then existing, but who had never supposed that what they had indicated in general terms, would be afterward made so definite and real to the public eye. Those untrue statements of my own, I must leave however just as they are, and rejoice that the great advance of science has led to the accurate knowledge of the great plateaus of which the civilized world then knew but little. One word more: I set the lower limit of plateaus of the second grade at 500 feet, lower therefore than the great master in Physical Geography set his.
“Elevations of the soil,” says Humboldt, “which do not display a marked difference in climate and vegetation from the country around them, are not rightly called plateaus.” His meaning is, that the name does not relate to absolute height measured from the sea, but harmonious climatic relations existing between contiguous districts, one of which is more elevated than the other. Highland and lowland are therefore to him words of unfixed meaning, if they do not stand in the contrast of height, climate, relief, and rates of temperature. Humboldt therefore did not consider the depression of Central Asia, at the Taringol, as a plateau; and table-lands from 200 to 1200 feet in absolute elevation, i.e. from the sea level, are passed over by him as not worthy of the same name which he applied to the plains 6000 to 10,000 feet above the sea.
Dealing as I do with the elementary features and the physical contrasts of countries which for the most part are now thoroughly explored, I prefer, for the purpose of elucidating the subject of Physical Geography, to consider the plateau as beginning at 500 feet above the level of the sea. By comparing the plateaus of both hemispheres it is not difficult to deal with a variety of features, and to make a number of discriminations which, without an absolute standard, it would be impossible to make.
We pass to the consideration of the much more varied and more imposing characteristics of mountains.