Page:Africa by Élisée Reclus, Volume 2.djvu/63

 CLIMATE. 46 difference is enormous, for it oftcm freezes on the plateaux. Snow is even said to have fallen in the Jofra oasis, as well as on the neighbouring hills. On the coast the heat and dryness of the air are daily tampered, at least from April to October, by the marine breeze, which blows regularly from the north- east in the same direction as the normal trade winds. It deflects gradually east- wards, and after an interval of calm the land breeze springs up, lasting the whole night, but towards the morning veering a little round to the west. Occasionally storms arise in this season, when the marine breezes become violent gales, dan- gerous to the shipping along the coast, on which the surf beats with great fury. During the winter months, which also coincide with the rainy season, the winds blow usually from the west, north-west, or north, and these also arc accompanied by storms. But far more dangerous, owing to their sudden appearance, are the abrupt transitions from north-east to south-west, generally followed by thunder and heavy rains. Of frequent occurrence are the calms, during which vapours accumulate in the air in such abundance that the sun becomes obscured, and the firmament is every- where overcast by a white veil of mist. In the Mediterranean basin there are few other regions where grey tints prevail so generally in the atmosphere. To catch a glimpse of the blue aerial spaces, the traveller must penetrate far into the interior of the coimtry. Here the vapours, instead of spreading in a uniform veil over the whole sky, are condensed into thick layers of dappled cloudlets. Nevertheless the skies of Tripolitana never acquire the serene azure which is so much admired in the temperate regions of Europe. The dust raised and dispersed throughout the atmosphere by the desert wind, at times in the form of the simoom, is held for weeks and months in suspension, always imparting to the heavens a slightly leaden effect. Vessels anchored in the port of Tripoli often find their decks strewn with sand by the storm, during which the town and the shore become wrapped in a thick fog or cloud, dry and parching rather than damp. Under the influence of the sandstorm, commonly called (jcbli, or "south wind," electricity is freely liberated. Sheltered in his tent, the traveller Stecker was on one occasion able to write his name in streaks of flame on the canvas covering. In the province of Tripolitana proper the mean annual rainfall is estimated at about eight inches, a proportion far exceeded in Mauritania and Cyrenaica, that is to say, the two regions projecting northwards to the right and left of the depres- sion of the Syrtes, In its pluvioraetric conditions Tripolitana thus belongs rather to the desert zone than to that of the coastlands. Heavy showers occur most fre- quently and in greatest abundance on the northern slopes of the Jebel Ghurian and of the other chains forming the scarp of the plateau. Henee in wealth of vege- tation the§e tracts rival the Algerian Kabylia itself, and might easily afford sustenance for a population of many hundred thousand souls. IJut in the oases of the plains it sometimes happens that tillage is suspended for years, owing to the absence of rain. Even moist fogs are rare, although here and there developed on the cultivated plateaux before sunrise, or spreading a fleecy veil over the palm groves of the oases. But however intensely dry the atmosphere usually is,