It is constructed on the western third of a vast mountain axis, which reaches in a broken and irregular course from the Sea of Japan to the Bay of Biscay. On the flanks of this range, peninsular slopes are directed toward the south, and extensive plateaus to the north. The culminating point in Europe is Mont Blanc, 16,000 feet above the level of the sea. The axis of elevation is not the axis of figure; the incline to the south is much shorter and steeper than that to the north. The boundless plains of Asia are prolonged through Germany and Holland. An army may pass from the Pacific to the Atlantic Ocean, a distance of more than six thousand miles, without encountering any elevation of more than a few hundred feet. The descent from Asia into Europe is indicated in a general manner by the mean The great path-zone. elevation of the two continents above the level of the sea; that for Asia being 1132 feet, that for Europe 671. Through the avenue thus open to them, the Oriental hordes have again and again precipitated themselves on the West. With an abundance of springs and head-waters, but without any stream capable of offering a serious obstacle, this tract has a temperature well suited to military movements. It coincides generally with the annual isothermal line of 50°, skirting the northern boundary beyond which the vine ceases to grow, and the limiting region beyond which the wild boar does not pass.
Exterior and interior accessibility.
Constructed thus, Europe is not only easily accessible from Asia, a fact of no little moment in its ancient history, but it is also singularly accessible interiorly, or from one of its parts to another. Still more, its sea-line is so broken, it has so many intrusive gulfs and bays, that, its surface considered, its maritime coast is greater than that of any other continent. In this respect it contrasts strikingly with Africa. Europe has one mile of coast-line for every 156 square miles of surface, Africa has only one for every 623. This extensive maritime contact adds, of course, greatly to its interior as well as exterior accessibility.
Distribution of heat in Europe.
The mean annual temperature of the European countries on the southern slope of the mountain axis is from 60° to 70° F., but of those to the north the heat gradually declines, until, at the extreme limit on the shores of Zembla, the ground is perpetually frozen. As on other parts of the globe, the climate does not correspond to the latitude, but is disturbed by several causes, among which may be distinguished the great Atlantic current—the Gulf Stream coming from America—and the Sahara Desert. The latter gives to the south of Europe an unduly high heat, and the former to Ireland, England, and the entire west a genial temperature. Together they press into higher latitudes the annual isothermal lines. If in Europe there are no deserts, there are none of those impenetrable forests seen in tropical countries. From the westerly shores of Portugal, France, and Ireland, the humidity diminishes as we pass to the east, and, indeed, if we advance into Asia, it disappears in the desert of Gobi. There are no vast homogeneous areas as in Asia, and therefore there is no widespread uniformity in the races of men.
And the quantity of rain.
But not only is the temperature of the European continent elevated by the Gulf Stream and the south-west wind, its luxuriance of vegetation depends on them; for luxuriance of vegetation is determined, among other things, by the supply of rain. A profusion of water gives to South America its amazing forests; a want inflicts on Australia its shadeless trees, with their shrunken and pointed leaves. With the diminished moisture the green gardens of France are replaced in Gobi by ligneous plants covered with a gray down. Physical circumstances control the vegetable as well as the animal world.
The westerly regions of Europe, through the influence of the south-west wind, the Gulf Stream, and their mountain ranges, are supplied with abundant rains, and have a favourable mean annual temperature; but as we pass to the eastern confines the number of rainy days diminishes, the absolute annual quantity of rain and snow is less, and the mean annual temperature is lower. On the Atlantic face of the mountains of Norway it is perpetually raining: the annual depth of water is there 82 inches; but on the opposite side of those mountains is only 21 inches. For similar reasons, Ireland is moist and green, and in Cornwall the laurel and camellia will bear a winter exposure.
There are six maximum points of rain—Norway, Scotland, South-western Ireland and England, Portugal, North-eastern Spain, Lombardy. They respectively correspond to mountains. In general, the amount of rain diminishes from the equator toward the poles; but it is greatly controlled by the disturbing influence of elevated ridges, which in many instances far more than compensate for the effects of latitude. The Alps exercise an influence over the meteorology of all Europe.
The number of rainy days;