ISLANDS. 9 



Limpopo. Other cavities below sea-level follow in succession between tbe Great 

 Syrtis and the Nile south of the plateau of Cyrenaica. At the foot of the Abys- 

 sinian hio-hlands on the Red Sea coast are also found deep troughs, the surface 

 waters of which have sunk to a level far below that of the neighbouring inlets. In 

 the southern section of the continent such maritime depressions do not occur. 



Islands. 



Africa is as poorly furnished with a complement of islands as it is with large 

 inlets and orographic systems. In their submarine relief those in the Mediterranean 

 belong rather to Europe than to this continent. Crete is connected with Asia 

 Minor and with Greece ; Sicily, Corsica, and Sardinia with Italy ; the Balearic 

 group by a submarine bank with the coast of Valentia ; Jerba alone and a few islets 

 in the Gulf of Cabes and along the Mauritanian shores form parts of the northern 

 seaboard. On the Atlantic side little occurs beyond some rocks and low-lying banks, 

 such as the Bissagos or Bishlas Archipelago, which a slight alluvial deposit or up- 

 heaval of the land would suffice to connect with the continent. The more distant 

 groups of Madeira and Porto Santo, the Canaries and Cape Verde Islands, are of 

 volcanic origin, and separated from the mainland by abysses over 3,000 feet in 

 depth. Of igneous formation are also the islets in the Gulf of Guinea, Annabom, 

 Saint Thomas, Prince, Fernando-Po, which form a chain of volcanoes all more recent 

 than the neighbouring mainland. 



The small groups in the Red Sea are mere coral reefs dominated here and there 

 by a few volcanic peaks. Even in the Indian Ocean the only real African island is 

 Socotra, the " spear-head " of the peninsula at present terminating at Cape Garda- 

 fui, and farther south Pemba, Zanzibar, and Mafia, disposed parallel with the 

 coast. The Comoro Group is of volcanic origiu, and Madagascar too far removed 

 from Mozambique to be regarded as a dependency of the continent. Its nearest 

 headland is 180 miles distant, and even this space is doubled for ordinary craft by 

 the velocity of the intervening marine currents. Its flora and fauna also show that 

 this great island belongs to a distinct geological domain. Geoffroy de Saint-Hilaire 

 looked on it as a world apart, and most subsequent zoologists have regarded it as a 

 fragment of " Lemuria," a vanished continent, which also embraced the granite 

 groups of the Seychelles and Rodriguez as well as Ceylon and the Maldives, and 

 may have even reached as far as Celebes in the Eastern Archipelago. 



Climate. 



Above all the great divisions of the globe, Africa is distinguished by the general 

 regularity of its climatic phenomena, a circumstance due to its massive form and 

 to its equatorial position. In the region approaching nearest to the northern or 

 southern lines of the equinoxes, rain falls throughout the year, thanks to the 

 opposing trade winds, which by neutralising each other often preserve the stillness 



