Not only the rivers of Northern Italy, but also the springs, or _fontanelle_, however small, which burst forth at the foot of the Alps, are utilised for purposes of irrigation. Virgil alludes to these springs in his Bucolics, where he says, “Children, stop the water; the meadows have drunk enough.” Lombardy is indebted to these springs for her fine prairies, or _marcite_, which sometimes yield eight crops a year. The great Adriatic plain has indeed undergone vast changes through the work of man. Originally it was a swamp surrounded by forests and heaths, but is now one of the best-cultivated countries of Europe. One of its great features consists in plantations of mulberries, the uniformity of which is relieved in many districts—and especially in the Brianza of Como, that {214} garden of Italy—by groups of tall trees, little lakes, and sinuous valleys. There still remain extensive heaths covering the moraines of ancient glaciers, which become more and more sterile from year to year; but the engineers are considering schemes for irrigating them by means of the fertilising waters of the Alpine lakes. The irrigated area in the valley of the Po nearly amounts to 5,000 square miles, and the water it absorbs every second is estimated at 35,000,000 cubic feet, equal to about one-third of the volume of the Po. If the proposed works of irrigation are carried out, the Po, which now plays so important a part in the economy of the country by its floods and alluvial deposits, will be reduced to the dimensions of a small river. The evaporation from the numerous rivers and canals of the country fills the air with moisture. Rains are less frequent than on the Atlantic coasts of England and France, but the clouds, driven by southerly winds against the cool slopes of the Alps, discharge themselves in torrents. The quantity of rain that falls in the upper Alpine valleys equals that of the most humid districts of Portugal, the Hebrides, and Norway, and the rainfall in the plains of Lombardy is equal to that of Ireland. The annual rainfall in the basin of the Piave is estimated at five feet, exclusive of what may evaporate or be absorbed by plants. These rains are not confined to certain seasons, though it has been observed that they are most abundant in May and October, and least so in February and July.[68]