The Bakalahari are a timid race, and in bodily development frequently resemble the aborigines of Australia. They have thin legs and arms, and large protruding abdomens, caused by the coarse indigestible food they eat. Their children’s eyes have no lustre, and such is their want of the animation so natural at that age that Dr. Livingstone never saw them at play. A Bechuana may meet a troop of Bakalahari, and domineer over the whole with impunity; but when he meets a Bushman he is fain to adopt a more humble tone, well knowing that if the request for tobacco is refused, the free son of the desert may endeavour to obtain it by a poisoned arrow. [Illustration: TOWER IN AGADES.] CHAPTER X. THE SAHARA. Its uncertain Limits--Caravan Routes--Ephemeral Streams--Oases-- Inundations--Luxuriant Vegetation of the Oases contrasted with the surrounding Desert--Harsh contrasts of Light and Shade--Sublimity of the Desert--Feelings of the Traveller while crossing the Desert-- Its charms and terrors--Sand-Spouts--The Simoom--The ‘Sea of the Devil’--The Gazelle--Its chase--The Porcupine--Fluctuation of Animal Life according to the Seasons--The Tibbos and the Tuaregs-- Their contempt of the sedentary Berbers. From the Nile to the Senegal, and from the vicinity of Agades or of Timbuctoo to the southern slopes of the Atlas, extends the desert which above all others has been named the Great. Surpassing the neighbouring Mediterranean at least three times in extent, and partly situated within the tropical zone, partly bordering on its confines, its limits are in many places as undetermined as the depths of its hidden solitudes. No European has ever travelled along its southern boundary, nor is its interior known, except only along a few roads, traced for many a century by the wandering caravans. In general the desert may be said to extend in breadth from the thirty-ninth to the seventeenth degree of northern latitude; but while in many parts it passes these bounds, in others fruitful districts penetrate far into its bosom, like large peninsulas or promontories jutting into the sea.