SANDS OP NOETHERN APRIOA. 629 



and gravel carried into tlie Mediterranean by the torrents of the 

 Maritime Alps, the Ligurian Apennines, the islands of Corsica, 

 Sardinia and Sicily, and the mountains of Calabria, is apparently 

 great. In mere mass, it is possible, if not probable, that as much 

 rocky material, more or less comminuted, is contributed to the 

 basin of the Mediterranean by Europe, even excluding the shores 

 of the Adriatic and the Euxine, as is washed up from it upon 

 the coasts of !N"orthem Africa and Syria. A great part of this 

 material is thrown out again by the waves on the European 

 shores of that sea. The harbors of Luni, Albenga, San Remo, 

 and Savona west of Genoa, and of Porto Fino on the other side, 

 are filling up, and the coast near Carrara and Massa is said to 

 have advanced upon the sea to a distance of 475 feet in thirty- 

 three years.^ Besides this, we have no evidence of the existence 

 of deep-water currents, in the Mediterranean, extensive enough 

 and strong enough to transport quartzose sand across the sea. It 

 may be added that much of the rock from which the torrent 

 sands of Southern Europe are derived contains Httle quartz, and 

 hence the general character of these sands is such that they must 

 be decomposed, or ground down to an impalpable slime, long be- 

 fore they could be swept over to the African shore. 



Sa/nds of Northern Africa. 



The torrents of Europe, then, do not at present furnish the 

 material which composes the beach-sands of Northern Africa, 



into a singularly heterogeneous conglomerate, that one deposit seems to be 

 consolidated into a breccia before the next winter's torrents cover it with an- 

 other. 



In the northern part of the peninsula there are extensive deposits of sand 

 intermingled with agate pebbles and petrified wood, but these are evidently 

 neither derived from the Sinaitic group, nor products of local causes known 

 to be now in action. 



I may here notice the often repeated but mistaken assertion, that the petri- 

 fied wood of the Western Arabian desert consists wholly of the stems of palms, 

 or at least of endogenous vegetables. This is an error. I have myself 

 picked up in that desert, within the space of a very few square yards, frag- 

 ments apparently of fossil palms, and of at least two petrified trees distinctly 

 marked as of exogenous growth both by annular structure and by knots. In 

 ligneous character, one of these almost precisely resembles the grain of the 

 extant beech, and this specimen was worm-eaten before it was converted into 

 eUex. 



* BOTxaER, Das Mittdmeer, p. 128. 



