THE NORTHEKN HiUllLANDS. 131 



sections. Instead of facilitating communication, as in the lowlands, ttie Abyssinian 

 rivers become so many defiles difficult to traverse, and often completely cutting off 

 two conterminous provinces for weeks and months at a time. 



Orographic System. 



From a geological point of view, the Ethiopian highlands present a striking 

 resemblance to those of Arabia facing them. The rocky formations are identical, 

 and consequently the mountains have much the same outlines, the same general 

 aspect, and almost the same vegetation ; while the populations, of common origin 

 on both plateaux, have been developed in almost identical surroundings. The back- 

 bone of the whole Ethiopian plateau, still appearing on some old maps under the 

 name of " Spina Mundi," is formed by the eastern edge of the mountains over- 

 looking the low coastlands of the Red Sea. For a distance of about 600 miles 

 this edge, precipitous on one side and developing a gentle incline on the other, 

 runs north and south nearly in the direction of the meridian. West of this range, 

 which also forms the water-parting, the whole of the plateaux gradually slope 

 towards the Nile, as indicated by the kwallas through which flow the waters of 

 the Mareb, Takkazeh, Beshilo, Abai, Jemna, and their affluents. On the eastern 

 slope the escarpments are intersected at intervals by the deep valleys of the 

 wadies rising on the plateau, which thus affords an accessible route to the heart of 

 Ethiopia ; but one river alone, the Awash, rises far west of the chain. The valley 

 of this watercourse describes a regular semicircle south of the Shoa highlands, 

 thus forming a natural barrier between the Abyssinian and southern Galla 

 territory. 



The Northern Highlands. 



In its northern section the axis of the range is scarcely sixty miles broad, 

 including the spurs and the lateral ridges. Its lowest eminences overlook the 

 plain of Tokar from the south, where the river Barka loses itself in a marshy delta. 

 Rising in abrupt terraces, it presents a steep face to the coast-line, which is here 

 indented by inlets and broken into rugged headlands ; the jagged crests leave only 

 a narrow passage at their base, blocked by rocks and interrupted by wadies 

 interspersed with quagmires. This region would prove an Ethiopian Thermopylae 

 for an army endeavouring to reach the mountain regions on this side. Farther 

 south the sea retires from the mountains, leaving a strip of lowlands known, as in 

 Algeria, by the name of Sahel, which stretches at a mean breadth of twelve miles 

 along the base of the gneiss, granite, and schist escarpments ; a few volcanic cones 

 are scattered between the hills and the seacoast, while lava-streams here alternate 

 with the sand and clay beds of the arid zone. The mountain range rises to a height 

 of from 4,000 to 6,000 feet above the Sahel, The Rora, as the parallel chains are 

 here called, expand in some places into plateaux, which, from the abundant rainfal 

 and fertility of the soil, would amply repay the labour of cultivation. Thus the Rora 



