Appendix, Number I.
By the pa.s.sage of the polar star over the meridian, the magnetic variation at Ankober was observed, with the aid of a well-regulated chronometer, to be 7 degrees westerly.
The longitude was determined both by a series of lunars, and by the eclipses of Jupiter"s satellites, the mean of upwards of 150 observations having been taken.
Appendix, Number II.
Remarks on the Natural History of that Portion of the Adel Country Situated along the Route from the Sea-Coast to the Frontier of Efat.
FROM TAJURA TO KILLULLOO.
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-sh.o.r.e, 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 sh.o.r.e, 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 ma.s.ses 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 a.s.sai 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 sh.o.r.e 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 const.i.tution 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 sh.o.r.es 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 ma.s.ses which have subsided into subterranean caverns. In the Bahr a.s.sai 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 a.s.sai, 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 sh.e.l.ls 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 const.i.tuents are indistinctly mingled; it is traversed by empty holes and bubbles, and occasionally by druses of zeolith. Coa.r.s.e quartz, sandstone, and conglomerates are sometimes found towards the surface. The country must have frequently been agitated by violent earthquakes, detaching huge ma.s.ses of rocks from the hills; and, bereft alike of vegetation and animal life, it presents altogether a most monotonous appearance.
The lower cla.s.ses 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 b.u.t.terflies 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-sh.o.r.e 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.
Amongst the Birds--
Of _Rapaces_: Perenopterus and Falco are numerous.
Of _Gallinacea_: Numida meleagris, and various partridges.
Of _Cursorii_: Struthio-camelus and Otis.
Of _Ciconidae_: Ciconia Marabu.
Of _Cantores_: Corvus, Loxia, Sylvia, Vidua.
Of _Mammalia_, three species of Antelope, one of Hyrax, one of Equus (Onager), one of Sus (Phacochaerus); and fresh holes in the sand indicated the presence of animals most probably of the order Rodentia.
The sheep of the country are the Hejaz lamb (Ovis aries laticaudata); white body and black head and neck, covered with hair, and having thick, short, fat tails; male without horns. The goats and cattle are generally small in stature, of all colours, and surmounted with very large horns. The shepherd dogs are small, and spotted with yellow and white; they have long pointed skulls like the fox.
With regard to the flora of this part of the country, the small quant.i.ty found in flower, belongs, with few exceptions, to the family of the _Leguminosae_, amongst which the order of _Mimoseae_ is the most extensive both in species and specimens; they are however all stunted and shrubby, and seldom attain any size. Still the only fuel and shade found during the journey was supplied by this tribe. There exist also several _Capparideae_; Cadaba, Sodada, Capparis. Cadaba rotundifolia is the most common.
The _Asclepiadeae_ are represented in the Stapelia pulvinata, which however was seldom found in blossom, and in the Pergularia tomentosa, with stately flowers and capsules.
The _Malvaceae_ existed in Ruitzia and Abutilon; and the other families found by the wayside, Moringeae, Rutaceae, Tamariscineae, Chenopodeae, Amaranthaceae, Cruciferae, presented only solitary specimens.
Of the _Euphorbiaceae_ there were but three; and of the Palm tribe there only appeared to be two species, the Phoenix dactylifera and Hyphaene crucifera, both of which gradually disappeared as the soil improved.
Nature has scattered the necessaries of existence with a n.i.g.g.ard hand over these desert plains, and the supply of water is indeed scanty. In such a hot climate, those pools which are not fed by running streams soon become adulterated by the decomposition of organic and inorganic matter. The wacke cannot resist any long exposure, and thence the water imbibes oxide of iron and muriate of soda, discovered in the pools of Goongoonteh, Allooli, and Bedi Kuroof; and again the numerous flocks and cattle of the caravans which are driven into the pools taint and corrupt the liquid in a still more offensive manner. The fetid smell and taste of the waters of Duwaylaka, Amadoo, Fialoo, and Killulloo, is indeed so oppressive as to be subdued only by a considerable quant.i.ty of spirit; and moreover the deposited mud, when stirred up, emits a volume of sulphuretted hydrogen. During the wet season all the lower parts of the country are said to be exceedingly unhealthy, violent storms and incessant rain in the plains and wadies forcing the inhabitants to retreat to the mountains.
FROM KILLULLOO TO THE FOOT OF THE ABYSSINIAN MOUNTAINS.
The desert of the Adaiel, spreading from the sea to the foot of the Shoan Alps, is not altogether a plain, as it has been most likely in remote ages, numerous wadies, with banks more or less high, now intersecting the greater part of it. These banks rise in some instances to hills of firm rock, generally wacke. They however consist of but lightly cemented conglomerates, or loose boulders. Towards the middle, as the ground rises, extinct volcanoes make their appearance, sometimes scattered and solitary, with indistinct cones and craters, completely covered with volcanic cinders, and sending off sheets of lava in all directions; or in whole cl.u.s.ters, with cones and craters complete, connected with each other, and environed by belts of their products.
The extensive plain of Eyroluf is a solid level of a dark, black, undecayed lava.
The tract of land between Killulloo and Dathara especially has been visited and overwhelmed by the action from below, which, having reversed the original disposition, has covered the surface with the effects of its violence. There is little to be seen of the under parts, although here and there some of the later formation, the residuum of the calcareous waters, has spread like a thin coat over the low grounds; but violent commotions have again and again altered and destroyed the first appearance, and it is now difficult to determine the centre pool from whence the fiery stream issued. In the absence of a main volcano and a main volcanic range, it may be concluded that, similar to some violent eruptions in South America, large mountains have been thrown up in the midst of former extensive plains, the fluid and half-fluid matter having burst forth wherever they were nearest to the surface.
Small extinct volcanoes were found on the plains of Sultelli and Eyroluf. The road pa.s.ses close to the isolated cone of one of these, called Jebel Helmund. The walls are straight and black, covered with several smaller cones of ashes; the hill itself is about four hundred feet in height; the crater is on the eastern side, a little below the top; and the sides, which are steep and sloping, are clothed with shrubs towards the base.
On the road to Moo stands a similar volcano; but the influence of these craters does not seem to have extended far beyond the immediate neighbourhood, although there is a connexion between the whole cl.u.s.ter on the plain of Mittur, which may be seen in the small lava streams and debris of volcanic product on the adjoining plains of Sultelli and Eyroluf. It is not, however, apparent that they alone have formed the present state of the surface, as the south-eastern side of the plains is terminated by a much older formation of wacke.
Between Meinha-tolli and Madera-dubba, obsidian, pumice, clinkstone, and fresh-water limestone containing sh.e.l.ls of Melania, were strewed about Excellent soil is found in all these situations, the low grounds being overflowed at some seasons, and, as in all volcanic countries, producing much vegetation. The extensive plains of Moolu and Burdudda are thickly covered with gra.s.s, and intersected by small brooks and pools, terminating towards the Hawash in very broken, hilly ground, and the large plain on the eastern bank of the river bears every sign of being annually deluged.
The country of the Adaiel is throughout very sparingly watered. During spring and autumn the hills collect sufficient rain-water for numerous rivulets, which after a course of scarcely one mile are absorbed by the sands, and dry up altogether by the end of the rains, whilst the deep hollows and clefts in the firmer rock preserve small quant.i.ties for the dry months of the year. The Hawash itself, although receiving all the rivers of Efat, and of the eastern declivity of the Shoan mountains, does not reach the sea. The banks, thickly overgrown, are about thirty feet in height, and very abrupt. Its fall is scarcely perceptible, yet the rush of the water is very considerable.
On the western bank volcanic hills and sheets of water again appear, the latter being situated lower than the bed of the stream. One of these, impregnated with alkali, is evidently an old crater filled up, and supplied by a hot mineral spring. The water is much esteemed for washing clothes; it possesses an hydrothionic smell and a bitter taste, resembling that of the salt of magnesia; but the borders are verdant, and a species of Cyperus grows luxuriantly in the water.
This portion of the country, though still sparingly supplied with the means of subsistence, is more favourable for specimens of zoology than the burning tract between Tajura and Killulloo.
Of _Beetles_ the family _Coprophaga_ had many representatives: Scarabaeus, Copris, Ateuchus, Onitis, Aphodius, Trox; Melolontha; four species of Cetonia (on the Aloe); one Silpha, Hister, Abax, Graphipterus, Anthia, Staphylinus, Elater, Cantharis, Erodius, Moluria, Pimelia, Mylabria, Chrysomela.
Of _Orthoptera_, large flights of Gryllus migratorius were observed near Azboti. Acrydium and Gryllotalpa very common throughout. Also many Neuroptera, and termite cone studding the face of the country.
Of _Acephala_ only one, Unio, was found near the Hawash.