stretched at their foot. But the system is also largely composed of the sandstone and limestone formations, which have been pierced by the eruptive lavas. South of the Black Harûj stretches an extensive calcurcous hamâda, or plateau, terminating north-east of the Murzuk depression in a group of cliffs and hills known as the Harûj-el-Abiad, or "White Harûj." Here, according to the Arab reports, are found the perfect skeletons of large marine animals.
Beyond the pass, which affords communication between the Zella and Fogha
oases on the northern and southern slopes respectively, the Harûj-el-Aswad is continued westwards by the Jebel-es-Soda, or "Black Mountains," already by Pliny designated by the synonymous expression, Mons Ater. According to the explanation of the Roman encyclopædist, this appellation, which has persisted for at least two thousand years, is due to the appearance of these uplands, which look as if blackened by fire, although, when lit up by the solar rays, they seem to be wrapped in flame.
