A traveler in central Arabia, speaking of a certain watercourse or "wadi," says: "Never within the memory of man had the wadi been known to flow. But during the summer of 1917 a flood of exceptional violence, descending from the mountains, burst through a barrier of sand dunes that had filled the old channel, and flowed down the long-dry wadi. The governor was seated in the audience chamber drinking coffee with his guests when they brought in the news.
' Bring me a cup and let me drink up this flood,' said he, thinking there was no flood. That eve ning, the first trickle of water reached Faraa, and for seven days a bread, swirling river flowed through the oasis, reaching a point some miles below its eastern extremity. For several months thereafter a deep and gradually evaporating lake stood where water had never been seen before. The havoc wrought by this flood was terrible. It completely wrecked many wells and de stroyed one small hamlet . . . 150 human lives, 450 camels, and thousands of sheep were lost." Thus many strange and unex pected things happen in deserts.
573. Desert springs.—Through cracks or breaks in the rocks, the water which falls on distant high parts of the mountains comes up in springs at some places along the foot of theAtlas and other mountains, or even far out in the desert. (Fig. 114.) From one spring to the next—sometimes a distance of several clays' journey—the caravans travel across this wide, white, glaring furnace. The springs are the stations on their route. The car avan leader must measure his march care fully, for although the caravan is on the move sixteen hours a day, it may cover during that wearisome time only about thirty miles.
574. Desert plants.—Everything that lives in the desert must learn to get along with but little water. The plants have deep roots which reach far down forwater. They aLso have small leaves, so that they do not give much moisture to the air. Some plants grow very quickly when it rains, and then make seed and die.
There are only a few plants, and many of these have a bitter taste, while others are so poisonous that no animal will eat them, or they are so thickly covered with thorns instead of leaves, that no animal can eat them.
575. Desert animals.—The animals are strangely fitted by nature to get alcong in such a place. The camel is a kind of living
storehouse. When he has a chance to get food and drink he takes so much that he adds a hundred pounds or so of fat to his hump. Then for a week at a time he can walk across the burning sands and neither eat nor drink, but each day pounds of fat stored in his hump go into his blood and take the place of food. In order that the camel may eat thorny bushes, his lips are shod with coarse thick hairs that lie flat. To avoid dust, he can shut his nostrils, as we shut our mouths. His eye has a double lid, one of which is almost transparent, so that he can see through it even in sand storms. Instead of a hard hoof, his foot is a wide, soft cushion that spreads out on the sand and keeps his feet from sinking in.
The desert sheep resembles the camel in its ability to store fat, but instead of a hump it has a broad, thick tail that often weighs half as much as the sheep itself. (Fig. 480.) Thedonkey, or ass, and the goat are natives of deserts, and, as we found in Section 561, the donkey requires much less food than the horse. Throughout the desert region there are wild antelope and wild gazelles. They do not store food on their bodies in the form of fat, but they can travel for long distances with astonishing speed, and thus escape their enemies and find food and water. Even the desert man can, like a camel, resist thirst. Many of the Sahara tribes are said to be able to go without water for four days, suffering little discomfort.
576. The nomads.—The desert does not have a clearly defined edge. In stead, it tapers off gradu ally into a country where there are patches of grass in the low places, and still farther from the desert good pasture lands, as described in See. 743.
Here on the edges of the desert live the nomads, people who have only flocks of sheep and goats, camels, donkeys, and a few horses. To get water and food for their animals they drive them from place to place. Many small tribes live by this means. They also buy things here and there, which they carry across the desert to sell. For ages nomads have carried negro staves across the Sahara, just as the band of Ishmaelites took the little boy Joseph down to Egypt 3000 years ago, and sold him to the Egyptians.