362 HEPORT— 1882. 



ascribed to the meteoric iron globules whicli occur in the sand of remote 

 localities, and under the most different conditions, as, for instance, in snow. 



These sandy superficial deposits form the last chapter of the geological 

 history of the Sahara, for, so far as I know, no well-ascertained traces 

 of the glacial period have been discovered either in Algeria or in the 

 Sahara-Lybian desert, so that the absence of the glacial period in those 

 parts of Africa furnishes an additional proof of the local and comparatively 

 limited character of this important phenomenon, a fact on which I have 

 repeatedly insisted in numerous publications.' 



But if after the formation of the superficial sandy masses the Sahara 

 had acquired the most prominent features of her present physiognomy, 

 still, since that time, not only the hydrographic and climatic, but also 

 some topographic conditions of that country have undergone very im- 

 portant modifications, as may be deduced from many facts, among which 

 I will mention only those pointed out by Rollaud and Clave. The first 

 calls our attention to the numerous incrustations of travertine, evidently 

 produced from sources which have disappeared, and to the immense 

 quantity of siliceous fragments worked and shaped by human hands, and 

 scattered about large tracts of the desert, where it is not likely that they 

 could have been distributed, if the now uninhabitable country were not 

 once inhabited. M. RoUand sums up the conclusions derived from a great 

 number of similar facts in the following words : ' The climate of Algeria 

 must have suffered a considerable deterioration since the times of the 

 Romans.' M. Clave is of the same opinion. He mentions with astonish, 

 ment the quantity of fragments of arrows made of polished flint, scattered 

 over the whole space between Biskra and Wargla ; and what is still more 

 significant, he has observed in the neighbourhood of Oglu-el-Kassi, 

 those fragments covered by a coating 16 inches thick of gypsum, 

 evidently deposited by sources of which all traces have vanished. ' Those 

 flint-fragments invested by gypsous incrustations,' says M. Clave, ' are 

 most probably the oldest known witnesses of human industry.' Now, the 

 Lybian desert j-ields to Dr. Zittel exactly similar conclusions. The 

 learned German geologist observes that between the oasis Chargeh and 

 the valley of the Nile, the basaltic tufa include leaves of plants, among 

 others, of the evergreen oak (Querctcs ilex), which no longer exist either 

 on the oasis or in Upper Egypt. ' Caves bristling with stalactites in 

 a country perfectly devoid of water,' says Dr. Zittel, 'but particularly 

 the polished and well-worked flints accumulated on different points of the 

 now thoroughly dry and empty desert, speak distinctly of a much more 

 favourable climate than the present one.' 



No doubt such climatic changes ascertained in the Sahara-Lybian 

 desert must suppose similar changes in the countries surrounding the 

 Mediterranean basin, as among others : Egypt, Syria, Asia Minor, &c. 

 And that is really the fact ; the arguments supporting it being as 

 numerous as convincing. It would not be consistent with the limits im- 

 posed on this paper to mention even a small number of them, so that I 

 must content myself with the following observations. 



In his remarkable work on the climate of the Mediterranean coun- 

 tries,^ Theobald Eischer, after having studied the changes which they 



' Une Page sur V Orient, pp. 2.51-272; La vi'getation du Glohe ; Espagne, 

 Algerie et Tunisie, pp. 429 et seq. 



^ Stiidien uber das Klima der Mediterraneen Lander, in Petermann's Mittheil- 

 »ngen, 1879. 



