xiv INTRODUCTION. 
Sudan, and a purely arbitrary limit to its southern extension may be placed in the 
neighbourhood of the sources of the Tumat, a branch of the Blue Nile, and of those of 
the Sobat, a leading affluent of the White Nile. The almost rainless region of Lower 
Nubia has had its northern limit placed at Assuan ; but as the crystalline mass of 
mountains that traverses it from south to north does not stop short there, but is 
continued along the so-called Arabian desert to Wadi Araba, the entire region 
between the Nile and the Eed Sea from Suakin to near the head of the Gulf of Suez 
may be dealt with as a whole ; there being, as has been already said, no natural 
barriers to interfere with the distribution of animal species, and the climate throughout 
being transitional. 
A brief outline will now be given of the main features of the entire area from the 
Bayuda Peninsula to Suakin, and northwards to the Delta. The first portion to be 
considered is the peninsula enclosed by the great curve of the Nile between Metammeh 
and Ambukol, occasionally erroneously called on maps the Desert of Bayuda, but which 
partakes in reality of the character of a savannah. From the position it occupies in 
the Nile Valley, it is a region in which the struggle between the southerly and northerly 
winds is felt in its full intensity. In days of great heat also it is subject to numerous 
whirlwinds, that rise in columns up to 45 metres, charged with fine dust, the product 
of the denuding action of the winds on the sandstones. It lies just within the area in 
which the periodical rains make themselves felt, but they are so slight that rain seldom 
falls on more than fifteen days throughout the year, the rainy season occurring between 
May and August. Sometimes, however, two consecutive seasons may be actually 
rainless. The rain is rapidly absorbed by the sandy soil, and in about 24 hours after 
its fall all trace of it is lost, except in the vivifying influence which it exercises on the 
parched vegetation. 
The now memorable route between Metammeh and Korti, over which a column of 
British troops marched in 1884, is described as almost perfectly level. It traverses 
an extensive plain with low ranges of hills, showing in places abundant signs of 
cultivation. Numerous wadis are passed through, in which long coarse grass and 
groups of acacia-trees are met with. The vegetation, sparse though it be, supports 
numerous herds of sheep, goats, and camels, the property of the nomadic Beduins 
who inhabit the district. The soil in places, during the rainy season, can be profitably 
cultivated, and there are numerous wells. To the east of this route the centre of the 
peninsula is occupied by a group of mountains (Jebel Magaga), consisting of primitive 
rocks, sandstones, and volcanic lavas and scoria;, similar to those found in the 
mountain-range along the coast of the Bed Sea. The peaks of these mountains are 
said to rise from 1014 metres to 1115 metres above the level of the sea. The half of 
the peninsula to the north-east of this central area of elevation has much the same 
characters as those met with along the Metammeh-Korti route. The western portion is 
