290 NORTH-EAST AFEICA. 



Climate. 



Nubia is divided into two climatic zones, whose limits, changing yearly, are 

 defined by the struggle between the northern and southern winds. In summer, 

 when the solar rays fall vertically on the soil between the equator and the northern 

 tropic, the southern winds follow the sun into the northern hemisphere, carrying 

 the rain-clouds with them ; but they scarcely ever reach the seventeenth degree of 

 latitude. The last periodical rains fall in the valley towards the junction of the 

 Atbara, the last tributary watercourse of the Nile. In this spacious region the 

 force of the southern winds is neutralised by that of the aerial currents blowing 

 from the north, the result of this struggle being the constant shifting of the 

 parting-line. 



Travellers across the Bayuda territory in May or June have to struggle 

 against the winds, being at one time forced from their course by the south wind 

 at another by that of the north, their way thus lying between two conflicting 

 tempests. However, the winds often blow alternately, that of the north prevailing 

 during the day and being replaced at night-time by that of the south. To the 

 south of this zone fall periodical rains, the more copious and longer in duration 

 the nearer the equator is approached. To the north, the soil is not watered by the 

 summer rains, being visited only by a few showers, which sometimes even cease 

 for several years together. When the northern winds predominate in the inter- 

 mediary zone and drive the opposing currents south of the usual limit, the drought 

 becomes general, bringing to the Nubians distant from the Nile famine, involun- 

 tary exile, and brigandage. 



The region of the border mountains, in the vicinity of the Red Sea, is more 

 favoured than the countries of the interior. The abundance of the vapours in this 

 littoral zone promotes the advance of the rain-bearing clouds towards the north. 

 Instead of stopping at the seventeenth degree of latitude, they extend as far as the 

 twenty- first degree of latitude, and beyond this limit occasional showers are 

 frequent ; but brought down by the northern winds they fall in winter, whilst the 

 opposed southern winds cause the moisture to be again precipitated in summer. 

 The result of this relative abundance of the rains on the coast region is a great 

 contrast between the Nubian districts near the Red Sea and those of the interior. 

 To the east the Arab nomads find abundance of wells, fountains, and pasturages 

 for their cattle ; but to the west nothing is visible but rocks and sands, the eye of 

 the traveller seldom lighting upon a grove of palms or mimosas, or any trailing 

 shrubs growing on the banks of the wadies. In some years the drought is so 

 complete that no shepherd dare venture into the desert. 



Nubia thus offers some well-defined natural divisions. The southern part of 

 the country, comprising nearly the whole peninsula of Bayuda, is a district of 

 steppes ; the coast of the Red Sea presents an analogous appearance, whilst all the 

 rest is desert and atmur, with the exception of the verdant and populous Nile 

 Valley lying between these two dreary wastes. In many places this valley is 

 reduced to a strip a few yards in width ; it even disappears altogether at the 



