278 ANNUAL OF SCIENTIFIC DISCOVERY. 



stretched from the Gulf of Cabes, in Tunis, to the west coast of Africa 

 north of Senegambia, having a width of several hundred 1 (perhaps, 

 where greatest, according to Mr. Tristram, 800) miles. The high 

 lands of Barbary, including Morocco, Algeria, and Tunis, must have 

 been separated at this period from the rest of Africa by a sea. All 

 that we have learnt from zoologists and botanists in regard to the 

 present Fauna and Flora of Barbary favors this hypothesis, and seems 

 at the same time to point to a former connection of that country with 

 Spain, Sicily, and South Italy. 



When speculating on these changes, we may call to mind that certain 

 deposits, full of marine shells of living species, have long been known as 

 fringing the borders of the Red Sea, and rising several hundred feet 

 above its shores. Evidence his also been obtained that Egypt, placed 

 between the Red Sea and the Sahara, participated in these great conti- 

 nental movements. This may be inferred from the old river- terraces, 

 lately described by Messrs. Adams and Murie, which skirt the modern 

 alluvial plains of the Nile, and rise above them to various hights, from 

 30 to 100 feet and upwards. In whatever direction, therefore, we look, 

 we see grounds for assuming that a map of Africa in the glacial period 

 would no more resemble our present maps of that continent than Europe 

 now resembles North America. If, then, argues Escher, the Sahara was 

 a sea in post-teruary times, we may understand why the Alpine glaciers 

 formerly attained such gigantic dimensions, and why they have left mo- 

 raines of such magnitude on the plains of Northern Italy and the lower 

 country of Switzerland. The Swiss peasants have a saying, when they 

 talk of the melting of the snow, that the sun could do nothing without 

 the Fohn, a name which they give to the well-known sirocco. This 

 wind, after sweeping over a wide expanse of parched and burning sand 

 in Africa, blows occasionally for days in succession across the Mediterra- 

 nean, carrying with it the scorching heat of the Sahara to melt the snows 

 of the Apennines and Alps. 



M. Denzler, in a Memoir on this subject, observes that the Fb'hn blew 

 tempestuously at Algiers on the 17th of July, 1841, and then, crossing 

 the Mediterranean, reached Marseilles in six hours. In five more hours 

 it was at Geneva and the Valais, throwing down a large extent of forest 

 in the latter district ; while in the cantons of Zurich and the Orisons it 

 suddenly turned the leaves f many trees from green to yellow. In a 

 few hours new-mown grass was dried and ready for the haystack ; for 

 although, in passing over the Alpine snows, the sirocco absorbs much 

 moisture, it is still far below the point of saturation when it reaches the 

 sub-Alpine country to the north of the great chain. MM. Escher and 

 Denzler have both of them observed, on different occasions, that a thick- 

 ness of one foot of snow has disappeared in four hours during the 

 prevalence of this wind. No wonder, therefore, that the Fohn is much 

 dreaded for the inundations which it sometimes causes. The snow-line 

 of the Alps was seen by Mr. Irscher, the astronomer, from his observa- 

 tory at Neufchatel, by aid of the telescope, to rise sensibly every day 

 while this wind was blowing. Its influence is by no means confined to 

 the summer season, for in the winter of 1852 it visited Zurich at Christ- 

 mas, and in a few days all the surrounding country was stripped of its 

 snow, even on the shadiest places and on the crests of high ridges. I 

 feel the better able to appreciate the power of this wind from having 



