History has left unrecorded the exact date of their arrival in Arabia; nor has she defined the period during which they remained tributaries, though often refractory, of the kings of Yemen. But in the fifth century of the Christian era there appeared among the Mustareb tribes a leader of extraordinary talent and energy named Kolaib, sprung from the tribe of Rabiah, who having, in the fashion of William Tell, slain with his own hand the insolent and licentious tax-gatherer sent them from Sana, raised the banner of general revolt in Nejd; and, in the battle of Hazat (500 A.D.), broke forever the bonds of Yemen from off the neck of the northern Arabs. This done, Kolaib aspired to unite his countrymen into one vast confederacy, over which he himself exercised for a time an almost kingly power; but the scheme was prematurely broken off by his own assassination. Left now without a master, but also without a ruler, the Mustareb tribes found themselves involved in a series of wars that lasted during the whole of the sixth century, their heroic period. Yet in spite of severe losses sustained in battle by this or that particular clan, their power as a whole went on increasing, till at the dawn of the seventh century they had wholly absorbed the feeble kingdom of Kindeh, and encroached yearly more and more on the narrowing bounds of Yemen, Irak, and Ghassan. [Illustration: AN ARAB CHIEF] Nor, probably, would they have stayed till they had become absolute lords over the whole, or nearly the whole, of the peninsula, had there not developed itself from among themselves a still more energetic element which, before many years had passed, reduced both northern and southern Arabs alike to common obedience, then raised them to an unexpected height of common glory, and at last plunged them, along with itself, into one comprehensive decline and ruin. This new and potent element was the well-known clan of Fihr or Koreish. Its families, of Mustareb descent, had at an early period, which subsequent and Mohammedan chroniclers have tried to identify with the fortunes of the mythical Ismail, established themselves in the southerly Hedjaz, near the town of Mecca, a locality even then the principal religious and commercial centre of Arabia. Already, at the beginning of the fifth century, the chiefs of Koreish had, by a mixture of violence and craft very characteristic of their race, rendered themselves the masters and the acknowledged guardians of the sacred “Kaaba.” This square stone temple, or rather shrine, itself of unknown antiquity, was situated within the precincts of the town of Mecca; and to it the Arabs were in the habit of bringing yearly offerings, and of making devout pilgrimages, for centuries before Mohammed had adopted it into the new ritual of Islam as the house of the true God. The keys of the consecrated building had originally been in possession of delegates appointed by the monarch of