There is a great diversity of cli matic conditions in the different regions of Italy, caused not alone by the difference in lati tude, but also the multiplicity of the ramifica tions of its principal mountain systems.
Italy is very long from north to south com pared with other countries. The German Em pire, for instance, covers less than 8° of lati tude; the kingdom of Italy, which is a little over half as large as Germany, covers more than 10°. Hence it follows that in the most northerly regions the sun does not set in certain places in summer until almost one and one-half hours later and in winter almost one and one-half hours earlier than in more southerly points. At the same time, however, the angle of inci dence of the sun's rays on the horizontal plane in various places becomes greater at all places in the south and attains to 10° more than in the north; and it exercises therefore a much stronger calorific influence. Therefore the longer continuance of heat of the long summer day in the north is made up for in the south by the greater intensity of the sun's rays and the continued clearness of the sky, and the difference in the summer temperature between the north and the south of Italy would tend to diminish, while in winter the greater length of the day as well as the greater intensity of the sun's rays combined produce a condition advan tageous to the southern portion, and the cli matic differences in winter between the two por tions of the country also caused by the sun in diverse latitudes will be more marked.
But to increase this meteorological diversity there enters the special oro-hydrographic con figuration of the country. The sea which sur rounds Italy, and which, except in the northern portion, is distant a maximum of almost 62 miles from any inland point, tends to lessen these extreme differences, but in very diverse ways according to the direction of the prevail ing winds, and the mountain ranges.
Thus the great northern plain enclosed on three sides by mountains, as if it were a great amphitheatre, sloping down and open toward the little Mor di Venezia, does not profit as much by the tampering action of the sea as the rest of that portion, whilst it is exposed almost without protection to the atmospheric influences from the interior of the eastern European continent ;• its climate becomes neces sarily aContinental,n i.e., extreme, with intense
cold in winter, and great heat in summer, no more than one might expect from its greater distance from the equator. In fact, the tem perature in Palermo in midsummer is 23°.9 centigrade; in Naples 23°.2; at Venice 23°.1; at Milan 23° • whereas in winter it is at Palermo; 8°.8 at Naples; 3°.7 at Venice; and 2°.2 at Milan. To this must be added the other great climatological factor of rainfall. The magnificent bulwark of the Alps which encircles Italy to the north acts as a powerful condenser of the moisture of the atmosphere, carried by the prevailing winds from the Tyrrhenian Sea, whence the enormous down fall of rain and snow which the year round feeds the numerous affluents on the left bank of the Po, and the rivers flowing into the Gulf of Venice. The amount of rain reaches in northern Law Maggiore (Cannobio) yearly 1,332 millimeTErs, and this is higher on the Carnic Alps (yearly 2,248 millimeters), where the currents of moisture from the Mediter ranean spend themselves, either surmounting the minor obstacle of the depression in the Ligurian Apennines, or avoiding this obstacle traveling by way of the long channel of the Adriatic. In Peninsular Italy, on the contrary, the special distribution of the Apennines and of the prevailing aerial currents produces a diversity of favorable conditions in the various regions. The Apennines and the other moun tains sloping toward the Tyrrhenian Sea are more frequently exposed to warm and damp currents deviating more or less from. south west direction, while on the Adriatic slope there is in winter exactly the opposite, and in sum mer a great variation of currents. Hence, in all the situated on the Tyrrhenian Sea from the Ligurian Riviera to the Gulf of Salerno there is a more copious rainfall. The regions at the base of the northern slope, on the contrary, have a smaller annual rainfall. Still smaller is the rainfall around the Plain of Foggia and near the Gulf of Tarentum, and in almost all the islands.