THE ANNALS MAGAZINE OF NATURAL HISTORY. [FOURTH SERIES.] No. 48. DECEMBER 1871. XLVII. — Memoir on the Hydrograj^Mcal System and the Freshwater Fish of Algeria. By Lieut. -Colonel R. L. Playfair, H.M. Consul General, and M. Letourneux, Conseiller a la Cour d'Appel, in Algeria*. I. Hydrographical System. In Europe an admirable system of circulation restores to the ocean the waters which the sun has taken from it, and which, having escaped from their aerial reservoirs in the clouds, are poured out on the surface of the earth. In every country a network of natural canals reunites into one central stream, and carries to the sea, the surplus of the rains and snows which have fertilized the soil, in the same manner that the venous system carries back the blood to the heart to be purified and to serve for the regeneration of the bodily organs. In Algeria, on the contrary, the system is far from being so simple : a very small part of the country is subject to ordinary hydrographic laws ; in the rest the waters either return to the clouds without passing through the sea or circulate in vast subterranean lakes. A glance at the map of Algeria will suffice to show that the country consists of three regions, as distinct in their hydrographical features as in their climate and vegetation : these are the Tell, the High Plateaux, and the Sahara. The first, occupying the littoral zone, Avith a breadth of from 50 to 70 miles, is for the most part mountainous, watered by copious rains, tempered by sea breezes, and possessing in a high degree the ordinary Mediterranean features. The flora and fauna of the eastern portion do not differ essentially from those of Sicily and Sardinia, while in the west they resemble rather those of Spain f. * Communicated by the Authors, having been read at the Meeting of the British Association in August 1871. t The separation of Spain from Africa hardly goes boynnd the limit of Ann.iL-Mag.X.If/st. Ser. 4. Vol. v in. 29
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