ADDRESS. 



Ixxi 



several hundred (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 favours this hypothesis, and seems at the same time 

 to point to a former connexion of that country with Spain, Sicily, and South 

 Italy. 



^Tien 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 huudi-ed feet above its 

 shores. Evidence has also been obtained that Egypt, placed between the 

 Eed Sea and the Sahara, participated in these great continental 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 heights, from 30 to 100 feet and upwards. In what- 

 ever 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-tertiary times, we may understand why 

 the Alpine glaciers formerly attained such gigantic dimensions, and why they 

 have left moraines 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 

 Eohn, 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 Mediterranean, 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 Fohn 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 Grisons it suddenly 

 turned the leaves of many trees from green to yeUow. 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 stUl 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 thickness of one foot of snow has dis- 

 appeared in four hours during the prevalence of this wind. No wonder, 

 therefore, that the Eohn is much dreaded for the sudden inundations which 

 it sometimes causes. The snow-line of the Alps was seen by Mr. Irscher, 

 the astronomer, from his observatory at Neuchatel, by aid of the telescope, 

 to rise sensibly every day wlule 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 Christmas, and in a few days all the suiTounding country was 

 stripped of its snow, even in the shadiest places and on the crests of high 

 ridges. I feel the better able to appreciate the power of this wind from 

 having myself witnessed in Sicily, in 1828, its effect in dissolving, in the 

 month of November, the snows which then covered the summit and higher 

 parts of Mount Etna. I had been told that I should be unable to ascend to 

 the top of the highest cone tiU the following spring ; but in thirty-six hours 

 the hot breath of the sirocco stripped off from the mountain its white mantle 

 of snow, and I ascended without difficulty. 



