632 A L P S of the chief deciduous trees oak, beech, ash, and syca more. These do not reach exactly to the same elevation, nor are they often found growing together; but their upper limit corresponds accurately enough to the change from a temperate to a colder climate that is further proved by a change in the wild herbaceous vegetation. This limit usually lies about 4000 feet above the sea on the north side of the Alps, but on the southern slopes it often rises to 5000 feet, sometimes even to 5500 feet. It must not be supposed that this region is always marked by the presence of the characteristic trees. The interference of man has in many districts almost extirpated them, and, excepting the beech forests of the Austrian Alps, a con siderable wood of deciduous trees is scarcely anywhere to be found. In many districts where such woods once existed, their place has been occupied by the pine and Scotch fir, which suffer less from the ravages of goats, the worst enemies of tree vegetation. The mean annual temperature of this region differs little from that of the British islands; but the climatal conditions are widely different. Here snow usually lies for several months, till it gives place to a spring and summer considerably warmer than the average of our seasons. 4. Subalpine Region, or Region of Coniferous Trees. This is the region which mainly determines the manner of life of the population of the Alps. On a rough estimate, we may reckon that, of the space lying between the summits of the Alps and the low country on either side, one quarter is available for cultivation, of which about one-half may be vineyards and corn-fields, and the remainder produces forage and grass. About another quarter is utterly barren, consisting of snow-fields, glaciers, bare rock, lakes, and the beds of streams ; and there remains about one-half, which is divided between forest and pasture, and it is the produce of this which mainly supports the relatively large popula tion. For nearly half the year the flocks and herds are fed on the upper pastures ; but the true limit of the wealth of a district is the number of animals that can be sup ported during the long winter, and while one part of the population is engaged in tending the beasts and in making cheese and butter, the remainder is busy cutting hay and storing up winter food. The larger villages are mostly in the mountain region, but in many parts of the Alps the villages stand in the subalpine region at heights varying from 4000 to 5500 feet above the sea, more rarely extend ing to about 6000 feet. The most characteristic feature of this region is the prevalence of coniferous trees, which, where they have not been artificially reduced, form vast forests that cover a large part of the surface. These play a most important part in the natural economy of the country. They protect the valleys from destructive ava lanches, and, retaining the superficial soil by their roots, they mitigate the destructive effects of heavy rains. In valleys where they have been rashly cut away, and the waters pour down the slopes unchecked, every tiny rivulet becomes a raging torrent, that cuts away and carries off the grausy slopes and devastates the floor of the valley, cover ing the soil with gravel and debris. In the pine forests of the Alps the prevailing species are the common spruce and the silver fir; on siliceous soil the larch flourishes, and surpasses every other European species in height. The Scotch fir is chiefly found at a lower level, and rarely forms forests. The Siberian fir is found scattered at intervals throughout the Alps, but is not common. The mughus, creeping pine, or Krummholz of the Germans, is common in the Eastern Alps, and sometimes forms on the higher mountains a distinct* zone above the level of its con geners. In the Northern Alps the pine forests rarely surpass the limit of 6000 feet above the sea, but on the south side they commonly attain to 7000 feet; and the larch, Siberian lir, and mughus often extend above that elevation. 5. Alpine Region. Throughout the German Alps the word alp is used specifically for the upper pastures, where cattle are fed in summer, but this region is held to include the whole space between the uppermost limit of trees and the first appearance of permanent masses of snow. It is here that the characteristic vegetation of the Alps is developed in its full beauty and variety. Shrubs are not wanting. Three species of rhododendron vie with each other in the brilliancy of their masses of red or pink flowers; the common juniper rises higher still, along with three species of bilberry; and several dwarf willows attain nearly to the utmost limit of vegetation. The upper limit of this region coincides with the so-called limit of perpetual snow, which demands further explanation. 6. Glacial Region. On the higher parts of lofty moun tains more snow falls in each year than is melted on the spot. A portion of this is carried away by the wind before it is consolidated ; a larger portion accumulates in hollows and depressions of the surface, and is gradually converted into glacier-ice, which descends by a slow secular motion into the deeper valleys, where it goes to swell perennial streams. As on a mountain the snow does not lie in beds of uniform thickness, and some parts are more exposed to the sun and warm winds than others, we commonly find beds of snow alternating with exposed slopes covered with brilliant vegetation ; and to the observer near at hand there is no appearance in the least corresponding to the term limit of perpetual snow. But the case is otherwise when a high mountain chain is viewed from a distance. Similar conditions are repeated at many different points, so that the level at which large snow-beds show themselves along its flanks is approximately horizontal. But this holds good only so far as the conditions are similar. On the opposite sides of the same chain the exposure to the sun or to warm winds may cause a wide difference in the level of permanent snow; but in some cases the increased fall of snow on the side exposed to moist winds may more than compensate the increased influence of the sun s rays. Still, even with these reservations, the so-called line of perpetual snow is not fixed. The occurrence of favourable meteorological conditions during several successive seasons may and does increase the extent of the snow-fields, and lower the limit of seemingly permanent snow; while an opposite state of things may cause the limit to rise higher on the flanks of the mountains. From these remarks it may be inferred that all attempts to fix accurately the level of perpetual snow in the Alps are fallacious, and can at the best approach only to local accuracy for a particular district. In some parts of the Alps the limit may be set at about 8000 feet above the sea, while in others it cannot be placed much below 9500 feet. As very little snow can rest on rocks that lie at an angle exceeding 60, and this is soon removed by the wind, some steep masses of rock remain bare even near the summits of the highest peaks, but as almost every spot offering the least hold for vegeta tion is covered with snow, few flowering plants are seen above 10,000 feet. There is reason to think, however, that it is the want of soil rather than climatal conditions that checks the upward extension of the Alpine flora. Increased direct effect of solar radiation compensates for the cold of the nights, and in the few spots where plants have been found in flower up to a height of 12,000 feet, nothing has indicated that the processes of vegetation were arrested by the severe cold which they must sometimes endure. The climate of the glacial region has often been compared to that of the polar regions, but they are widely different. Here, intense solar radiation by day, which raises the
surface when dry, to a temperature approaching 80 Fahr.,
