The advanced state of the season was unfavourable for observations in
the department of natural history. Both animal and vegetable life were
apparently in a state of torpor; the trees and shrubs were in general
leafless; and no annual plant whatever was to be seen, even in the
immediate vicinity of the watering-places. The few insects that were
not in a state of chrysalis, seemed drowsily to procrastinate their
existence until food for the new generation should be prepared by
nature. Amphibia, Saurii, and Ophidii, which are generally not so
dependent on a supply of water, existed in small numbers in their
lurking-places, whilst birds and larger animals must at this season have
migrated to more favoured countries.
Basaltic and trachytic hills, either isolated or in chains, rise at a
distance of about half a mile from the sea-shore, which is winding and
shelving. The hills are in general rounded, and marked by broad veins
of similar composition, but containing more perfectly crystallised
felspar, quartz, and zeolith. They have not the sharp peak, but are
broken and cliffy, and have apparently been upheaved at different
periods.
On leaving the shore, a most striking specimen of columnar basalt
presented itself in the ravine of Galeylafeo, 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 Warelissan,
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
Bahr 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
Bahr 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 Bahr 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 Adaiel 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.
Of _Diptera_ and _Hemiptera_: several species.
Of _Lepidoptera_: two species of Papilio and several of moths; and it
was a matter of great wonder whence these butterflies obtained food in a
country where even one flower could not be discovered.
Of _Myriapoda_: one Iulus, and several Scolopendra.
_Arachnida_ were in great numbers: Mygale, Epeira, Lycosa, and one small
Androctenus.
Of _Crustaceae_: near the sea-shore a Pagurus existed in astonishing
numbers, and in the sweet waters a Daphnia.
_Vertebrata_ were still scarcer; and the _Reptilia_ had their
representatives in the three orders Saurii, Ophidii, and Batrachii. A
small lizard, very agile, existed under stones; also serpents, Vipera
and Coluber, and in moist places Bufo and Rana.