The principal rivers are the Boyana, issuing from Lake Scutari, and consequently regarded as a continuation of the Montenegrin Moratcha, the Drin, formed by the confluence of the White and Black Drin, which, flowing respectively to the south and north through a long valley at the foot of the Shar range, take a westerly direction after their junction, the Matia, the Arzen, the Shkumb (ancient Genusos), the Simen (Apsos), formed by the junction of the Devol and Ergene, the Viossa (Aous), which owing to the trend of the Khimara range takes a north-westerly direction, the Kalamas (Thyamis) and the Arta (Arachthos), flowing south into the Ambracian Gulf.
The highest peaks are found in the Simen (or Semien) and Gojam ranges.
The Simen Mountains lie N.E.
Lefebvre, charged (1839) with political and geographical missions, and Captains Galinier and Ferret, who completed for him a useful triangulation and survey of Tigre and Simen (1840-1842).
Shortly afterwards Kassa moved against Tigre, defeated Ubie's forces at Deragie, in Simen (February 1855), took their chief prisoner and proclaimed himself negus negusti of Ethiopia under the name of Theodore III.
Shoa had already shaken off his yoke; Gojam was virtually independent; Walkeit and Simen were under a rebel chief; and Lasta, Waag and the country about Lake Ashangi had submitted to Wagshum Gobassie, who had also overrun Tigre and appointed Dejaj Kassai his governor.