450 NOETH-WEST APEIOA. refuge in these inaccessible recesses, where they defend themselves as in a strong- hold, and whence they can conveniently sweep down on the surrounding districts. The ruling tribe of the Ahaggars are the Kel-llhelas, who occupy the central parts of the plateau, the rallying-place of the whole confederation. The authority of its amghar, or chief, is also acknowledged by all the other tribes throughout these highlands. The Northern Imohaghs. Nearly all the Ahaggars are pastors, a very small number occupying themselves with agriculture. Duveyrier estimates at thirty thousand at the utmost all the northern Tuaregs, or a little over a thousand persons per tribe. The territory roamed over by them has a superficial area of about 400,000 square miles, being in the proportion of one square mile to every thirteen persons. Most of the Tuaregs are of tall stature, with slim figures and robust constitu- tion. Naturally of fair complexion, they acquire a bronze tint in the sun. But although differing little from southern Europeans in colour and the regularity of their features, they can always be distinguished by their slow but somewhat jerky gait, long stride, and haughty carriage of the head. Duveyrier compares their attitude to that of the ostrich or of the camel, and attributes it to the habit of con- stantly carrying a lance. Some of the Tuaregs have blue eyes, and amongst the women this colour of the iris is considered a great mark of beauty. Amongst the Imohaghs no sickly persons are met. The feeble, the infirm, those subject to rickets and other con- stitutional ailments, are soon carried off, while by the law of " the survival of the fittest " those who remain are the better able to endure a life of hardship and resist the ravages of disease. Hence centenarians are by no means rare amongst them. The Tuaregs are doubtless indebted to their extremely temperate habits for their excellent health. Amongst other terms of reproach they heap upon the Arabs is that of being " great eaters." While on the march they themselves take one meal only during the day, and two while sojourning under the tents. Corn, dates, and figs, the berry of the salviulora peraica, some herbs, and a little meat, form their frugal faie. By traditional usage they are forbidden the use of birds or fish, the flesh of these animals being reserved for the exclusive enjoyment of the marabuts. Their most ordinary complaints are rheumatic affections and ophthalmia, disorders easily explained by the habit of sleeping on the sands during the night, and by their constant exposure to the action of the solar rays reflected from the dunes. Amongst the populations of the desert, the features connected with the organ of vision differ from those characteristic of the inhabitants of the oases. . Extremely dense eyebrows overshadow the ball of the eye, which is small and deeply sunk in the socket, with very long lashes, a whitish circle separating the cornea from the sclerotic. The whole presents a slightly reddish tint, due to the suffused state of the blood-vessels. • In order to protect the sight from the glare of the solar rays, and at the same time guard against the dust constantly rising from the sands, the Tuaregs have
