Page:Africa by Élisée Reclus, Volume 2.djvu/541

 LAKE lOHABO. 448 flowing as a perennial stream round the eoAtom foot of the Udan plateau. Then, after receiving some uffluentH from the Eguereh (liiitrict, it« course i« continued between the Northern Tubsili und the Iruwen Mountains down to the alluviul pluinn which stretch north of the Devonian plateaux. So far it« course is quite clear, and its slope perfectly regular. Near the Temassinin zawya, at the southern foot of the zone of chalk formations, its betl stands at an absolute altitude of l,'2o0 feet. Here it is joined, if not by the waters, at least by the fonnerly fl(Midi-<l valleys, which have their source in the central depressions of the Northern Tujwili plateau. The main outlines of these affluents of the Igharghar, the We<ls Ighurgharen and Issawan, are clearly indicated by chains of dunes, high banks, windings, and serpentine meanderings in the sands. Further north is also distinctly seen a breach or gorge traversing the region of cretaceous formations. But further on the incline soon becomes indistinct. It becomes uncertain whether its course is continued northwards, and it is impossible to say in whut direction the wuter would flow were the depressions again flooded. Nor in this section of the WchI Igharghur hu« any current been seen in the memory of man. What at first seems to look like a river- bed running between banks, with a breadth varying from 1 to G miles, becomes further on completely merged in the surface of the surrounding desert. It is a mere succession of hollows interrupted by sandhills, and in many places the vulky has been entirely closed by the shifting stmds. According to Duveyrier, the junction of the Ighargharen and Ighurghar is effected by un underground channel flowing beneath the dunes. Lake Miiiaro. Numerous lakes are scattered over the cavities in the Northern Tassili district, and in the outer cirques, where the torrents take their rise. Duveyrier haa suggested that these lakes are old craters of extinct volcanoes, where the waters have gradually collected. But this cannot at all events be the case with the meres usually designated by the name of " Lake " Miharo, and even by the natives sjwken of as ki/n; or " seas." These flooded depressions, which were visittnl in the year 187G by Von Bary under the escort of a Tuareg from Rhat, are nothing more than the hollows in the channel of a wady, where the water remains throughout the year. AVhen it flows in sufficient abundance from the hillside, these pools become united in one basin, which during the dry season is again broken up into a number of separate jxinds. In the vicinity rise some gastnjus springs, which the natives have named Sebarhbarh, or the " Garglings," from the bubbles incessantly rising from the bottom and bursting on the surface. According to Von Bary. the water of these springs, without reaching the boiling-ix.int, as asserte<l by the Tuaregs, is slightly thermal, with a normal temi)erature excetnling 200^^ F. The German explorer saw no crocodUes in the Miharo ponds, but detected very distinct traces of thdr presence. These saurians, which are much dreade<l by the surrounding nomads, do not appear to exceed G or 8 feet in length, judging at least from the imprint of their feet.