Sometimes the Arabs ride on a white ass, mounted on a side saddle. They also ride the camel with a single hump, and from it good milk and wool are obtained. It can travel eighty miles per day and goes for a week without water; but it never learns to know or love its master. Jackals, panthers, and hyenas prowl about the desert, which is also infested with ants, scorpions, and locusts, as well as a horrible kind of spider with double pincers. The Arabs are called the sons of Ishmael. They are traders and workers in leather. They are calm and dignified in appearance, and have never been conquered. Thirteen centuries ago these Arabs were divided into a great number of tribes who made war upon each other. Then Mohammed arose, and proclaimed that he was a prophet sent by God to teach the Arab people, and through them to convert all the world to a new religion. He suffered much persecution at first, but in the end he overcame all his enemies and ruled the whole of Arabia. He destroyed all idols, and taught his people to give up alcoholic drinks, gambling, and usury. His successors, who were called Khalifs, went forth to conquer the world. Those who would not be converted to the Mohammedan religion they forced to pay heavy taxes, those who resisted by force of arms they slaughtered without mercy, but those who became Mohammedans they rewarded with a share of their booty and power of government. They captured Damascus and Jerusalem, they conquered Egypt and North Africa, and besieged Constantinople. In the end they conquered Spain in the west and Persia in the east, so that their Empire stretched from the Atlantic Ocean to India. The Arabs destroyed many kingdoms, but they also knew how to build. They founded great cities, the most glorious of which was Bagdad on the river Tigris, where Harun-al-Rashid reigned and Queen Scheherazade told her tales of goblins, battles, and treasures, and Aladdin worked his wonderful lamp. They also founded Cairo, within sight of the Egyptian pyramids, and made it the capital of Egypt after they had pillaged Alexandria. But Mecca in Arabia, where Mohammed first preached his new doctrine, remains the centre of the Mohammedan religion to this day. [Illustration: Fig. 13.--View of Mecca in the Seventeenth Century.]