CLIMATE OF ALGEIUA. 221 Stoppage of the supplies sometimes occur, as in the Hodna district, in 1862, when un underground shock suppressed two wells and reduced the volume of a third by one-half. Thanks to this increase of irrigating waters, the oases have been largely extended, and M. Holland alone has planted as many as forty thousand palms in reclaimwl districts. Other fruit trees have been doubletl ; the crops have increased in pn>- jwrtion, and new plants have been introduced in the gardens. New villages have sprung up amid the {Milm groves ; the jwpulation of the lluaras has been doubled, and the tents of many nomad tribes have been converted into fixed habitations grouped round about some newly created oasis. The siime i)roccss may also be applied in many places to the development of thermal and mineral springs, thua increasing the already abundant supply of medicinal waters in Algeria. It might even be possible to utilise the subterranean sources for pisciculture, the wells of TJrlana, Mazer, and Sidi Amran having revealed the presence of several varieties of fishes, crustaceans, and freshwater molluscs. Efforts are also being made to prevent the waste of the surface waters, which are lost by evaiwration or infiltration in the sands and crevices of the rocks. 80 early as the year 1801, a first barrage was constructed in the gorges of the Meurad, above Marengo in the west Mitija plain. Since then large dykes have been raisetl in the Macta basin, and for many years an extensive barrage has been in progress, which is intended to intercept the waters of the Wed Ilamiz south-east of Algiers. Similar works are being erected in the Shalif basin or its affluents, as well as on other rivers of Algeria. On the completion of the schemes already projected, all the streams rising in the uplands will be arrested at their entrance on the plains by means of dams diverting the current to lateral channels. But these works, some of which are stupendous monuments of human enterprise, are not unattended with danger. The two great reservoirs of the Sig and the Habra have already burst through their barriers, the tumultuous waters overflowing on the surrounding plains, wasting the cultivated tracts and sweeping away houses and villages. IJut the havoc caused by these disasters is partly compensated by the fresh supply of alluvial matter thus spread over the exhausted soil. Climate of Algeria. The diflFerences of climate correspond to those of the relief, aspect, and latitude of the land. Each of the several zones — maritime strip, coast range, central plateau, southern slope, and desert — has its special climate, variously modifying the shifting curves of temperature, moisture, and other meteorological pheno- mena. Algiers, lying about the middle of the north coast over against Provence, may be taken as typical of the maritime region. On the whole, its climate may be described as mild and temperate, although very variable, owing to the sudden changes of the atmospheric currents. According to M. Bulard's observations, it« mean temperature is about G0° F., fulling ia January to O-i^, and in August, the
