Them Is however a tract across the desert, in which these dangers are comparatively small. It lies between 13' and 16' E. long., and owes its advantages partly to its climate and partly to its sorb It is remarkable that this tract occurs where no elevated country lies between the Mediterranean and the Sahara, but only the low range of the liarntah, which join. that arm of the Sahara that reaches the shores of the Mediterranean. The country along the shores of the Gulf of Sidra, between 12' and 19' E. long., and between the Gulf and the Sahara, does not appear to rise in any part more than 1000 feet, and in most parts it is ranch lower. Through this gap the northern winds, which frequently blow a gale, and bring moisture from the countries north of the Mediterranean, which at that season are drenched with rain, find access to the Sahara, and produce a con siderable degree of cold even as far south as Mourzuk. To these winds also we may probably ascribe the rain which falls in this season in the kingdom of I ezzan, and renders it the most fertile tract of the Sahara. Them rains appear to extend to 21' N. lat., and as the northern limit of the tropical rains occurs near 16' N. lat., the tract between the two limit, of rain does not exceed 5 degrees of latitude, whilst in other places it occupies more than double that extent. The advantages of this tract as a thoroughfare for cafilas consist in the smaller extent of the sandy tracts and of the continuous or broken ridges of rocks. Though the rocky parts within the rainless region resemble the sandy tracts in being without vegetation, the wells which occur between them are more numerous, and rarely more than a few days' journey from one another. The road through this country gives the easiest access to the interior of Africa from the north. This road, after leaving the town of Tripoli, runs south-east to the northern boundary of Fezzan, over a country which partakes in some degree of the nature of the Sahara, presenting a succession of plains and ridges of hills. The hills are of inconsiderable height, generally not exceeding 400 feet, and never rising above 600 feet. Many of them consist of lime stone overtopped by lava ; others are only sand-hills. They are without vegetation, but contain between them many fertile valleys. This country, which extends to the town of Sokna in Fezzan, has abundance of wells and water. South of this place extends the Ilarutsh Assouat, or Mona Niger, occupying a width of about 35 miles in a straight line. Faxen, which extends from this mountain tract to the northern tropic, consists of numerous small oases separated from each other by com paratively narrow tracts of sand. [FEzzarr.] Water is abundant, except towards the southern boundary, where a level desert occurs, which can only be traversed in four days ; but in the middle of it there is a small place called Gatrone, enrrounded by sandy hills and mounds covered with small trees. At Kasrowa and Tegerhy there are extensive plantations of date-trees and abundance of water. From the southern boundary of Fezzan to the town of Bilma, or from 23° to 18' 30' N. lat., a continuous ridge of steep rocky hills, elevated from 300 to 500 feet above the plain, runs almost due north and south ; and from 5 to 20 miles mat of this ridge there are isolated hills, mostly composed of sand, but in some places of rock. Between these rocks the road runs over a stony plain withont the least vegetation, but Denham says that after the rains a grass quickly springs up, which is several feet high, and that the rains fall in torrents as far as the Tiggerindunnna Dills It would therefore appear that in this tract the northern rains extend to 21° N. lat. No part of this country is inhabited, but wells of drinkable water occur at distances of three or four days' journey. Near 19° N. lat. however there are several small towns or villages, which owe their existence not so much to a certain degree of fertility in the soil, as to numerous small lakes which lie along the foot of the rocky range, and in which trona crystallises. In the vicinity of some of these lakes there are groves of date-trees and pasture-ground for cattle. In some parts the soil is covered with incrustations of pure trona, which extend for several miles in every direction. In a few places mimosa-trece are Sound. Bilma is noted for its extensive salt-pits (Brutal and in its vicinity there are a few spots covered with vegetation. South of Bilma the road runs over loose hills of fine sand, in which the camels sink nearly knee-deep. The hills sometimes disappear in a single night by the drifting of the sand, and all traces of the passage, oven of a large caravan, vanish in a few hours. Wells are rare. After four days' travelling from Bilma the walla of DNA are met with; and after four days more those of Aghadem. The last-mentioned wells are abundant, and situated in a wooded valley, which however is not inhabited. After three days more the country is reached which enjoys a small portion of the tropical rains, and the soil improves. At first the sandy soil is inter spersed with clumps of grass, and here and there with low bushes; trees soon appear, and then Increase in number. Thus the desert ceases
near 16' N. lat., but no permanent habitations are met with until the vicinity of Lan is reached, a town which is situated a short distance from Lake Tchad (14' 20' N. lat.). The desert between Bilma and LaH L called the Desert of Tintnma.
The tract just noticed as traversing the desert from north to south, divides the Sahara into two unequal portions, of which the western and larger is known among the natives by the name of Sahel, and the eastern and smaller among geographers by that of the Libyan Desert.
Cocut.—Until lately many misconceptions prevailed respecting this coast, which extends perhaps more than 1200 miles along the Atlantic.
Modern surveys of the shore have shown that nearly the whole of the coast is elevated, and consists of sandstone, which in most parts rises to the height of 100 feet and more, but in some does not exceed 60 or 80 feet. A low coast only occurs between Cape Mirik (19° N. lat.) and the mouth of the river Senegal, but hbre, as at some other parts of the coast, dunes, er sand-hills, are found at no great distance from the shore, and behind these the flat country seems to have a con siderable elevation above the sea. The whole coast, as far south as Cape Blanco, is free from sand-banks and shoals, and has regular soundings. The depth gradually increases from the beach, and at the distance of 4 miles there are from 30 to 34 fathoms ; at 12 Idles from 50 to 60 fathoms; and at the distance of 30 miles about 100 fathoms. The water then deepens very suddenly. A large sand-bank however extends from Greyhound Bay N. lat.) to Cape MiHk; it is known by the name of the Bank of Arguin, and on it the French frigate 3ledusa was lost in 1816. The currents generally follow the direction of the coast. East of Cape Juby is a sudden bend of the coast, which is the most dangerous place in the whole coast-line, as the swell is almost invariably from the north-west, and consequently almost directly on the coast; besides this, the fine particles of sand which cover the desert being blown into the sea and mingling with the haze occasioned by the heavy surf, render this coast very indistinct. The greatest strength of the ourrent is usually at the distance of 3 to 6 miles from the land, and it gradually decreases as it recedes from it The wind generally blows from the north-west or west, and frequently in hard gales, especially in the night. It is supposed that the rarefaction of the air produced by the arid soil of the Sahara being heated to an extraordinary degree by the almost perpendicular rays of the sun, gives rise to the westerly winds along the coast of the Sahara.
Soil.—The Sahel, or western part of the desert, is by far the worst part of the Sahara. It does not appear that in all this vast extent a single oasis occurs the soil of which is fit for agriculture or for the growth of date-trees. The soil however varies greatly, passing from a fine to a coarse sand and gravel, and then gradually to a bare layer of broken stones and rocks. In many places hills of moderate eleva tion occur. Some of them consist of sand, and are subject to be changed in size and form by the winds ; others consist of rocks, frequently of granite and quartz. All these soils are destitute of vegetation, which only appears in the depressions between the hills and sometimes at the base of the rocky elevations, but it consists only of a few grasses and shrubs. There appear to be numerous tracts, though of small extent, which are fit for pasture ; for, according to all accounts, the number of individuals who find subsistence in this part of the Sahara is considerable, and they subsist altogether on the pro duce of their herds. It is stated, and with some degree of probability, that the caravan-road has been purposely formed through the worst part of the desert, the merchants being less afraid of the dangers of the country than those which they would have to encounter if they traversed a tract which is inhabited by numerous independent tribes, each of which is eager to enrich itself by plundering the caravans or subjectiug them to a heavy tax for a free passage through their terri tories. It would appear that at no great distance from the sea the country contains extensive pasture-grounds, though of very inferior quality, and frequently interrupted by tracts which are completely sterile. Farther inland desert tracts entirely destitute of vegetation and inhabitants are scattered over a much greater portion of the country, but it is perfectly sterile and uninhabited only along the caravan-road, so that the cafilas generally terminate their long journey without meeting with a single person. The different tracts covered with sand, gravel, and rocks, as well as the ridges of low hills which occur along the caravan-road, run east and west, a fact which may perhaps be accounted for by the circumstance of the wind almost without exception blowing from the east. The country between this road and the above-mentioned country between Tripoli and LaH is inhabited by numerous tribes of Tuaricks.