account of the intense action of the sun by day and the rapid cooling by radiation by night, as in all elevated regions. The absolute humidity decreases with the altitude, and is greater in summer than in winter. The relative humidity, and, consequently, the degree of cloudiness, is least in winter in the Alps, while in the surrounding region the relative humidity and cloudiness are usually greatest in winter.
On the north side the annual rainfall is from 25 to 40 inches; but this increases irregularly to about 90 inches on the southern side, where the steep slopes deflect upward the mois- ture-laden warm winds from the Mediterranean Sea. The average annual rainfall for the whole region cannot be far from 60 inches, while that of the surrounding lowlands is less than 35 inches. Where the high mountains have a copious rainfall on the windward side, the val- leys on the leeward side experience a deficiency; so that on one side of a mountain range the rain- fall may be many times that on the other side. Of the total annual rainfall throughout the Alps about 18 per cent. occurs in the spring and about 25 per cent. in winter. In summer the pro- portion decreases from 37 per cent. in the north- ern part to 25 per cent. in the south; but in the fall, on the contrary, the proportion increases from 20 per cent. in the north to 33 per cent. In the south. In the higher Alps much of the pre- cipitation is of course in the form of snow, which is carried down to lower levels by glaciers and is there melted. The snow line in the Alpine moun- tains undergoes an annual variation, reaching its lowest altitude, about 2000 feet, toward the end of January, and its highest altitude, in the neighborhood of 9500 feet, about the middle of August. The limit differs for the northern and southern exposures, the snow line on the south- ern slopes lying over 150 feet higher in mid- winter, and about 1300 feet higher in the early fall. At low altitudes of 2000 to 3000 feet, the snowy days much exceed the number of days on which the ground remains snow-covered, but at altitudes of 8000 feet, the first snow commonly remains throughout the season of snow. The lower limit of perpetual snow is at an altitude ranging from 8500 feet to 9500 feet.
The general winds of the Alps follow the cyclonic and anti-cyclonic laws, which give a veering through the south when the cyclones pass to the north, as they usually do, and through the north when the cyclones pass to the south. Local winds are very prevalent; among these the mountain and valley winds, blowing upward from the valleys by day and downward from the mountains by night, are the most characteristic. In the Central and Northern Alps occur these hot, dry winds called the föhn. These are the result of descending air on the leeward side of the mountains after much of the moisture has been condensed by the cold high up on the windward side. These föhn winds, while a source of discomfort to the inhabitants, are welcomed in the spring, for they clear the ground of snow much more rapidly than the sun can accomplish it. Such is the evaporating power of the föhn winds that it may cause two feet of snow to disappear in half a day.
Fauna. The large native animals of the Alps are becoming scarcer and scarcer, by reason of the increasing number of sportsmen and the fact that the exploration habit, which is here practiced by tourists as in no other part of the world, has left scarcely a valley in untrodden seclusion. The wild cat, the brown bear, and the wolf have been driven into the more remote recesses, and are gradually becoming rare. The chamois and the ibex are found among the higher mountains, the haunts of the latter being among the inaccessible rocky solitudes bordering on the snow line. The pursuit of these animals is the most exciting and dangerous of European hunting sports. Foxes, weasels, and Alpine hares are plentiful, while otters and ermines are less numerous. The badger is common in the lower Alps, but the marmot is more distinctively an Alpine habitant, and it seems to maintain its numbers, and flourishes along with some smaller rodents in the higher altitudes even up to the snow line, the Alpine snow mouse having been found up to an altitude of 12,000 feet. The birds of the lower Alps are very numerous, consisting of the adjoining European species, and among the higher mountains are to be found eagles, hawks, and owls, and the smaller birds, choughs, snow finches, and larks. The great lammergeyer, once quite common in the higher Alps, has now become almost extinct. Game birds, such as woodcock, grouse, and partridges, are fairly abundant. Reptiles are not numerous. The lakes of the Alpine region contain a large variety of fishes; trout, salmon, and in some localities species of whitefish being the most important. Insects of all kinds flourish in the Alps. Butterflies and beetles are numerous, and extend up to snow altitudes. With increase of elevation, however, their colors become more and more subdued, and they become more and more deficient in wing power, thus necessitating a closer contact with the ground than prevails in like species below.
Flora. The forms of plant life of the Alps differ with the altitude, ranging from those com- mon in Europe, at lat. 46°, to those typical of the arctic regions. The main subdivision of the Alpine plant growth is therefore into altitudinal zones: with increase of altitude there is a corres- ponding poleward change in the flora. The Alpine slopes are noted for their verdure up to the limits of vegetation: at low altitudes are the forests and meadows, while above these are the shrub and flower-decked pastures, which are such an im- portant feature both in the landscape and in local life. At the base of the Alps on the south side, the lemon and olive flourish; but on the whole the prosperous growth of the vine may be taken as the most significant indication of plant life. With the grape occur the hardy plants of Central Europe, grains, and the princi- pal deciduous trees, oak, beech, ash, sycamore, maple, chestnut, and walnut. These latter are to be found up to an altitude of 4000 or 5000 feet, when they give way to the coniferous trees, which, while plentiful only up to an altitude of 0000 to 7000 feet, are in places found at still greater elevations, where the fir, the larch, and the creeping pine are the chief species seen, together with shrubs of Central and Northern Europe. The Alpine roses and violets are cele- brated for their beauty. The typical Alpine plants, those which grow above the tree line, in some instances up to the region of eternal snow, are characterized by a low, clumpy growth which sends forth at the proper season flower stalks which bear beautifully colored flowers. The blossoms of many species have peculiar hairy or woolly coatings. Gentians, violets, Alpine bells,
