sections. Instead of focilitatinp communication, as in the lowlands, the 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 backbone of the whole Ethiopian plateau, still appearing on some old maps ubder the name of "Spina Mundi," is formed by the eastern edge of the mountains overlooking 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 iwirallel 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
