On leaving the shore, a most striking specimen of columnar basalt presented itself in the ravine of Galeylaféo, which, for nearly half a mile, runs through the heart of a huge mountain. In width it is about 200 yards, and the perpendicular pillars are 200 feet in height. It is evident that water could not have been the sole agent in producing such a huge cleft, although at present the ravine presents the appearance of a regular water-course. The surrounding hills consist of the same rock, but covered with loose boulders, which are much stained with oxide of iron.
Amongst the confusion of volcanic masses on the plain of Warelissán, excepting in some rare cases, when the true lava stream could be traced to its source, it was difficult to determine the exact site of the craters from whence they had been ejected. The hill which separates Báhr Assai from the sea, with its singular tops of limestone, slate, and creta, deserves a more minute examination than could be given at this season of withering heat. The western side is the most interesting, as being more open and disclosed; there is, however, as in all formations in the vicinity of volcanic countries, no uniform inclination of the layers. The range bordering the eastern shore of the lake is basalt and basaltic wacke; on the western, it is partly gypsum and limestone, but resting on basalt.
The great salt lake is a deep extensive basin, separated by an immense lava stream from the remainder of the bay, the head of which it once formed. Resembling the Dead Sea in the depression of its level, in the density and chemical constitution of the fluid, and in the loneliness, sterility, and desolation of its borders, it yet differs from it materially in the ways by which volcanic action has produced the strange phenomenon of the existence of shores so considerably below the level of the ocean. In the Dead Sea, the lake of Tiberias, and the valley of the Jordan between them, it has apparently been a distortion and crushing of immense masses which have subsided into subterranean caverns. In the Báhr Assai it has been produced by the erection of a new bank, serving as a dam or barrier across the head of a long narrow bay, by which a considerable body of sea-water was separated from the former common receptacle. As high as the level of the Arabian Gulf are to be found, in the basin of Báhr Assai, the salts and earthy (magnesian) precipitates of the salt water, which in the course of time was reduced to its present level by evaporation, the yearly supply of rain-water being but as a drop to the ocean. Huge heaps of lava, having been apparently in strife with the opposite element, are erected on the banks over wacke, or in other cases over a finely-grained soft mart. The latter, when clear of lava, presents a thin layer of gypsum, with numerous shells of Melania, Limnaeus, Physa, Planorbis, Cyclostoma, Unio, and Cycas, some of which are at present to be found in the distant fresh-water pools and rivulets.
The shallow water on the borders of the lake presents natural salt-pans, and a crust of fine salt, two inches thick and tolerably clean, covers nearly the whole of the surface. The supply would seem to be inexhaustible; for when cut out with a spaddle, a new crust is soon furnished from the waters beneath. Being visited by almost every tribe of the Adaïel and Somauli, and unhappily situated on the borders of the most lawless and savage of them, this remarkable spot is almost forbidden ground for the observer, not to speak of the obstacles thrown in the way by the destructive temperature and the general absence of the necessaries of life.
In the ravine of Goongoonteh, and during the continuation of the journey as far as Killulloo, slight variations of trap formation were met with. The wacke is of a fine grain, and its constituents are indistinctly mingled; it is traversed by empty holes and bubbles, and occasionally by druses of zeolith. Coarse quartz, sandstone, and conglomerates are sometimes found towards the surface. The country must have frequently been agitated by violent earthquakes, detaching huge masses of rocks from the hills; and, bereft alike of vegetation and animal life, it presents altogether a most monotonous appearance.
The lower classes of animals, of ephemeral existence, are found on every living or vegetating body.
Of Coleoptera were observed: two species of Pimelia (longipes), one of Cetonia, of Copris (Isidis), of Erodius (gibbus), several Staphylini and one Gyrinus.
Of Orthoptera: Locusts, Blattidae, Mantidae, Truxalidae.
Of Hymenoptera; several bees, especially at Killulloo, one of which, marked with light brown segments on the abdomen and bearing a long sting, was exceedingly annoying.
Of Piezata: many different ants.