second range sends a chain (the Harrar hills) eastward to the Gulf of Aden. The two chief eastern ranges maintain a parallel course S. by W., with a broad upland valley between—in which valley are a series of lakes—to about 3° N., the outer (eastern) spurs of the plateau still keeping along the line of 40° E. The southern escarpment of the plateau is highly irregular, but has a general direction N.W. and S.E. from 6° N. to 3° N. It overlooks the depression in which is Lake Rudolf and—east of that lake—southern Somaliland. The western wall of the plateau from 6° N. to 11° N. is well marked and precipitous. North of 11° N. the hills turn more to the east and fall more gradually to the plains at their base. On its northern face also the plateau falls in terraces to the level of the eastern Sudan. The eastern escarpment is the best defined of these outer ranges. It has a mean height of from 7000 to 8000 ft., and in many places rises almost perpendicularly from the plain. Narrow and deep clefts, through which descend mountain torrents to lose themselves in the sandy soil of the coast land, afford means of reaching the plateau, or the easier route through the Hawash valley may be chosen. On surmounting this rocky barrier the traveller finds that the encircling rampart rises little above the normal level of the plateau.
(2) The aspect of the highlands is most impressive. The northern portion, lying mainly between 10° and 15° N., consists of a huge mass of Archaean rocks with a mean height of from 7000 to 7500 ft. above the sea, and is flooded in a deep central depression by the waters of Lake Tsana. Above the plateau rise several irregular and generally ill-defined mountain ranges which attain altitudes of from 12,000 to over 15,000 ft. Many of the mountains are of weird and fantastic shape. Characteristic of the country are the enormous fissures which divide it, formed in the course of ages by the erosive action of water. They are in fact the valleys of the rivers which, rising on the uplands or mountain sides, have cut their way to the surrounding lowlands. Some of the valleys are of considerable width; in other cases the opposite walls of the gorges are but two or three hundred yards apart, and fall almost vertically thousands of feet, representing an erosion of hard rock of many millions of cubic feet. One result of the action of the water has been the formation of numerous isolated flat-topped hills or small plateaus, known as ambas, with nearly perpendicular sides. The highest peaks are found in the Simen (or Semien) and Gojam ranges. The Simen Mountains lie N.E. of Lake Tsana and culminate in the snow-covered peak of Daschan (Dajan), which has an altitude of 15,160 ft. A few miles east and north respectively of Dajan are Mounts Biuat and Abba Jared, whose summits are a few feet only below that of Dajan. In the Chok Mountains in Gojam Agsias Fatra attains a height of 13,600 ft.
Parallel with the eastern escarpment are the heights of Baila (12,500 ft.), Abuna Josef (13,780 ft.), and Kollo (14,100 ft.), the last-named being S.W. of Magdala. The valley between these hills and the eastern escarpment is one of the longest and most profound chasms in Abyssinia. Between Lake Tsana and the eastern hills are Mounts Guna (13,800 ft.) and Uara Sahia (13,000 ft.). The figures given are, however, approximate only. The southern portion of the highlands—the 10° N. roughly marks the division between north and south—has more open tableland than the northern portion and fewer lofty peaks. Though there are a few heights between 10,000 and 12,000 ft., the majority do not exceed 8000 ft. But the general character of the southern regions is the same as in the north—a much-broken hilly plateau.
Most of the Abyssinian uplands have a decided slope to the north-west, so that nearly all the large rivers find their way in that direction to the Nile. Such are the Takazzé in the north, the Abai in the centre, and the Sobat in the south, and through these three arteries is discharged about four-fifths of the entire drainage. The rest is carried off, almost due north by the Khor Baraka, which occasionally reaches the Red Sea south of Suakin; by the Hawash, which runs out in the saline lacustrine district near the head of Tajura Bay; by the Webi Shebeli (Wabi-Shebeyli) and Juba, which flow S.E. through Somaliland, though the Shebeli fails to reach the Indian Ocean; and by the Omo, the main feeder of the closed basin of Lake Rudolf.
The Takazzé, which is the true upper course of the Atbara, has its head-waters in the central tableland; and falls from about 7000 to 2500 ft. in the tremendous crevasse through which it sweeps round west, north and west again down to the western terraces, where it passes from Abyssinian to Sudan territory. During the rains the Takazzé (i.e. the “Terrible”) rises some 18 ft. above its normal level, and at this time forms an impassable barrier between the northern and central provinces. In its lower course the river is known by the Arab name Setit. The Setit is joined (14° 10′ N., 36° E.) by the Atbara, a river formed by several streams which rise in the mountains W. and N.W. of Lake Tsana. The Gash or Mareb is the most northerly of the Abyssinian rivers which flow towards the Nile valley. Its head-waters rise on the landward side of the eastern escarpment within 50 miles of Annesley Bay on the Red Sea. It reaches the Sudan plains near Kassala, beyond which place its waters are dissipated in the sandy soil. The Mareb is dry for a great part of the year, but like the Takazzé is subject to sudden freshets during the rains. Only the left bank of the upper course of the river is in Abyssinian territory, the Mareb here forming the boundary between Eritrea and Abyssinia.
(3) The Abai—that is, the upper course of the Blue Nile—has its source near Mount Denguiza in the Gojam highlands (about 11° N. and 37° E.), and first flows for 70 m. nearly due north to the south side of Lake Tsana. Tsana (q.v.), which stands from 2500 to 3000 ft. below the normal level of the plateau, has somewhat the aspect of a flooded crater. It has an area of about 1100 sq. m., and a depth in some parts of 250 ft. At the south-east corner the rim of the crater is, as it were, breached by a deep crevasse through which the Abai escapes, and here develops a great semicircular bend like that of the Takazzé, but in the reverse direction—east, south and north-west—down to the plains of Sennar, where it takes the name of Bahr-el-Azrak or Blue Nile. The Abai has many tributaries. Of these the Bashilo rises near Magdala and drains eastern Amhara; the Jamma rises near Ankober and drains northern Shoa; the Muger rises near Adis Ababa and drains south-western Shoa; the Didessa, the largest of the Abai’s affluents, rises in the Kaffa hills and has a generally S. to N. course; the Yabus runs near the western edge of the plateau escarpment. All these are perennial rivers. The right-hand tributaries, rising mostly on the western sides of the plateau, have steep slopes and are generally torrential in character. The Bolassa, however, is perennial, and the Rahad and Dinder are important rivers in flood-time.
In the mountains and plateaus of Kaffa and Galla in the south-west of Abyssinia rise the Baro, Gelo, Akobo and other of the chief affluents of the Sobat tributary of the Nile. The Akobo, in about 7° 50′ N. and 33° E., joins the Pibor, which in about 812° N. and 33° 20′ E. unites with the Baro, the river below the confluence taking the name of Sobat. These rivers descend from the mountains in great falls, and like the other Abyssinian streams are unnavigable in their upper courses. The Baro on reaching the plain becomes, however, a navigable stream affording an open waterway to the Nile. The Baro, Pibor and Akobo form for 250 m. the W. and S.W. frontiers of Abyssinia (see Nile, Sobat and Sudan.)
The chief river of Abyssinia flowing east is the Hawash (Awash, Awasi), which rises in the Shoan uplands and makes a semicircular bend first S.E. and then N.E. It reaches the Afar (Danakil) lowlands through a broad breach in the eastern escarpment of the plateau, beyond which it is joined on its left bank by its chief affluent, the Germama (Kasam), and then trends round in the direction of Tajura Bay. Here the Hawash is a copious stream nearly 200 ft. wide and 4 ft. deep, even in the dry season, and during the floods rising 50 or 60 ft. above low-water mark, thus inundating the plains for many miles along both its banks. Yet it fails to reach the coast, and after a winding course of about 500 m. passes (in its lower reaches) through a series of badds (lagoons) to Lake Aussa, some 60 or 70 m. from the head of Tajura Bay. In this lake the river is
