SWITZERLAND, with an area of 15,976 square miles, may be divided into three physical regions—the Alps, the Central Plateau, and the Jura—which extend across the country from south-west to north east. The Alps, which cover about three-fifths of the whole of Switzerland, rise in places to great heights, but are penetrated by the longitudinal valleys of the Rhine, the Rhone, the Inn, and numerous other rivers, so that their topography is very varied. The Central Plateau, whose area is about one-half that of the Alpine region, has been much cut up by the rivers which flow across it, and its height ranges from 1,000 to 3,000 feet above sea-level ; it consists of Tertiary sandstones generally covered by glacial deposits which frequently provide a fertile soil. The Jura, which occupies the remainder of the country, is of limestone forma tion, and has an average height of about 3,000 feet ; it has been thrown into a great series of folds, which run nearly parallel to one another and present a serious barrier to communications.
CLIMATE.—The climatic conditions of Switzerland vary greatly with altitude, with the slope of the land from, or towards, the sun, and with the direction of the prevailing winds. The mean tempera ture of the plateau in January ranges from about 32°F. in the
lowlands to about 26°F. in the uplands, and in July from about 68°F. in the former districts to about 62°F. in the latter. The temperature on the mountains decreases with increasing elevation, and over considerable areas snow lies throughout the year, while in the Jura the climate is somewhat more severe than at similar altitudes on the Alps. Several factors which introduce local varia tions, frequently of considerable economic importance, may be noted. The larger lakes exercise a modifying influence upon the winter temperatures of the land in their vicinity ; the difference in mean temperatures on the two slopes of a valley, one of which faces the sun while the other looks away from it, frequently corre sponds to a difference of many degrees in latitude ; the Fan winds hasten the spring in the valleys down which they blow. The precipitation varies greatly from one place to another, but over the plateau it is generally between 30 and 40 inches, while on the Alps it is as a rule much greater, though some of the Alpine valleys are so sheltered from the rain-bearing winds that irrigation is necessary.