SAHARA 



75 



mountainous parts embrace many deep valleys, 

 most of them seamed with the dry beds of ancient 

 rivers, as the Igharghar and the Mya, both going 

 some hundreds of miles northwards towards the 

 'shotts' (see below) of Algeria and Tunis. These 

 valleys always yield an abundance of water, if not 

 on the surface in the watercourses, then a shurt 

 distance below it, and are mostly inhabited, and 

 grazed by the cattle and sheep and camels of the 

 natives. Another characteristic type of Saharan 

 landscape is a low plateau strewn with rough 

 blocks of granite and other rocks, and perfectly 

 barren. These elevated stone-fields, called ' ham- 

 mada" the best known is the Hammada el-Homra, 

 south-east of Ghadames and on the border of Tri- 

 poli alternate with tracts of bare flat sand, with 

 broad marshes, where water has stood and evapor- 

 ated, leaving salt behind it, and with extensive 

 tracts of small, polished, smoothly-rounded stones. 

 In very many parts of the Sahara, especially 

 in the valleys of the mountainous parts, in the 

 recesses or bays at the foot of the hills, alongside 

 the watercourses, and in the hollows of the sand- 

 dunes, in all which localities water is wont to exist, 

 there are oases habitable, cultivable spots, islands 

 of verdure in the midst of the ocean of desert. 

 These oases occur in greatest number along the 

 southern face of the Atlas and the Algerian moun- 

 tains, on the northern side of the Ahaggar plateau, 

 and along certain definite lines, the chief of which 

 extend between Murziik in Tripoli and Lake Tsad, 

 t h" l;:liarghar and Sokoto by way of Air, the Ighar- 

 ghar and the bend of the Niger by way of Timissao, 

 Morocco and Cairo by way of Tafilet, Tuat (Ain- 

 salah ), and Ghadames, and Morocco and Timbnctoo 

 by way of Tenduf and TandenL These lines of 

 oases mark the great caravan-routes IxHween the 

 central Soudan states and the Mediterranean. 



A large portion of the Sahara, though not the 

 whole, was undoubtedly under water at one time, 

 proliiibly in the Cretaceous period and earlier. 

 Then the surface seems to have been in great part 

 elevated, so that the water remained only in some 

 lakes and in gulfs near the Mediterranean coast. 

 The physical features that at present characterise 

 the Sahara are undoubtedly due in their broad essen- 

 tials to atmospheric, chemical, and even mechanical 

 causes, and only in a very small degree to the 

 action of water. Water has exercised scarcely 

 any influence on a large scale here since the Ter- 

 tiary period ; and there can lie no doubt that a 

 process of desiccation, similar to that which is 

 now going on in the Turkestan deserts, has been 

 in operation throughout the whole of this region 

 from the earliest historic time. The Romans nod 

 colonies or military posts a long way southwards, 

 in what are now desert regions ; and both Herodo- 

 tus and Pliny tell us that the elephant, the rhino- 

 ceros, and the crocodile, all animals that only live 

 near abundant supplies of water, were common 

 throughout North Africa in their day. None of 

 the Egyptian inscriptions or animal-sculptures 

 represent the camel, nor do the Greek and 

 Roman historians mention it either as being a 

 denizen of North Africa. The camel is now the 

 principal carrier across the Sahara, and must 

 nave been introduced since the beginning of the 

 Christian era. The inference from these and other 

 facts is that the process of desiccation has gone on 

 more rapidly during the last 2000 years. The posi- 

 tiun of the sand-dunes is determined by the un- 

 changeable configuration of the surface ; the wind 

 ami chemical action do all the rest. The sand 

 itself is simply the Saharan rocks (granite, gneiss, 

 mica-schists, and cretaceous rocks) ground to 

 'ln*t. The great heat by day causes the rocks to 

 expand ; the great fall of the temperature at night, 

 combined with the enormous evaporation that then 



takes place, makes them split and crack, and break 

 into pieces ; and the strong, often violent, winds 

 use these fragments like files, or even sand-blasts, 

 with which to grind to pieces other rocky frag- 

 ments. The terrors of the desert sand-storm have 

 been often described (see DESERT). Thick deposits 

 of Saharan quartz sand-dust were discovered by the 

 Challenger on the floor of the Atlantic a long way 

 west of the African coast. The sand in the dunes 

 is so dry that in several places the tread of a camel 

 or a man will make the hill hum, or even thunder, 

 as a vast quantity of it slips down to a lower level. 

 The range of temperature is exceedingly great : 

 often the thermometer falls from considerably more 

 than 100" F. during the day to iust below freezing- 

 point at night. In the west of the Sahara the daily 

 average is 85 in the shade in the month of May. 

 Rain does fall in certain parts of the Sahara 

 with more or less frequency ; but in most districts 

 on the average after intervals of two to five years. 

 After a fall ot rain it is not unusual to see the river- 

 beds in the mountainous regions filled with foam- 

 ing torrents. But the atmosphere is so dry and 

 clear that objects can lie seen and sounds heard at 

 a vast distance. The Mirage (q.v.) is no un- 

 common feature. Owing to this extreme dryness 

 of the air, the Sahara, especially where it is reached 

 by the prevailing west and north-west winds, is 

 very healthy. 



"flie plant-life is very rich in the oases, the date- 

 palm, which has its home in these regions, being 

 the principal ornament as well as the most valu- 

 able possession of these fertile spots. But fruit 

 trees, as oranges, lemons, peaches, figs, pome- 

 granates, &c., are also grown, with cereals, rice, 

 durrha, millet, and such-like food crops. In the 

 desert regions the plant-life is confined principally 

 to tamarisks, prickly acacias and similar thorny 

 shrubs and trees, salsolacew, and coarse grasses. 

 The animals most commonly met with include the 

 giraffe, two or three kinds of antelope, wild cattle, 

 the wild ass, desert fox, jackal, hare, lion (only on 

 the borders of the desert), ostrich, desert lark, 

 crow, viper, python, locusts, flies. The people 

 keep as domestic animals the camel, horse, ox, 

 sheep, and goat. 



The human inhabitants, who are estimated alto- 

 gether at between 1,400,000 and 2,500,000, consist 

 of Moors, Tuareg, Tibbu, Negroes, Arabs, and 

 Jews. The Moors and Tuareg are both Berbers 

 (q.v. ) ; the former live between Morocco and Sene- 

 gal, the latter in the middle, south of Algeria and 

 Tunis. The Tuareg are great traders, and control 

 the principal caravan-routes. The Tibbu, who 

 number about 200,000, and are regarded as being 

 ethnically intermediate between tlie Berbers and 

 the Negroes, occupy the oases between Fezzan and 

 Lake Tsad. The Arabs of pure stock are very 

 few ; they have become mixed with the Berbers 

 and the Negroes. The most valuable products 

 of the Sahara are dates and salt, the latter col- 

 lected on the salt pans, and made from the rock- 

 salt of Taudeni in the west, and of Kawar (Bilma) 

 in the east ; the remaining products are horses, 

 soda, and a little saltpetre. But for many long 

 years there has been a very active trade carried on 

 by caravans, between the central Soudan and 

 Niger countries and the Mediterranean states, the 

 ivory, ostrich-feathers, gums, spices, musk, hides, 

 gold dust, indigo, cotton, palm-oil, shea-butter, 

 kola-nuts, ground-nuts, silver, dates, salt, and 

 alum of the interior lands being exchanged for 

 the manufactured wares (textiles, weapons, gun- 

 powder, &c. ) of Euro|>ean countries. The French 

 desire to get this trade into their own hands, 

 and are proposing to construct a trans-Saharan 

 railway, light and of narrow gauge, from the 

 coast to the shores of Lake Tsad and the Niger. 



