From this period we find a constant rise and fall of dynasties. While Imams alternately held and lost authority, there were springing up, generally to disappear, princes in many parts of the country, so that at times the Yemen was divided into a number of principalities. Celebrated amongst these were the Sulayhites and the Zurayites, of whom the latter for centuries held possession of the southern province of Aden. But, meanwhile, in the north the Imams were succeeding one another with the usual rapidity of oriental sovereigns, and with very varied authority. In the fifth century A.H. we find the Abyssinian line again in possession of Zebeed, at this time the principal city of the Teháma. Meanwhile the Zaidi family of Rassites continued to govern at Sadah without serious interruption. In 1173 A.D. the then reigning Sultan of Sanaa surrendered his power to Turan Shah, brother of Salah ed-din (Saladdin), the Ayyubite Caliph of Egypt; and Ali, son of the Sultan El-Mansur Hatim, was nominated governor of that city. It would be out of place here to trace the long lines of governors and rulers who dominated the Yemen during the next two centuries. A few names, however, are remembered to-day, and mentioned by authorities as being men of great power or culture. The first is El-Muzaffer, who united for the time at least all the Yemen under his sway, and who died at the end of the thirteenth century; and again, Abdul-Wahab, who reigned early in the sixteenth century, and founded many colleges at Sanaa, Taiz, and Zebeed, and built a number of cisterns and aqueducts at places where water was scarce. During the next period of the history of the Yemen, we come in contact for the first time with European traders and the Turks, who were destined in no small degree to influence the future of the country. About the year 1445 A.D. the Christian king of Abyssinia sent a mission to Florence, and a famous missive to the priests of Jerusalem. This king is well known to history from these two acts alone, and to-day is celebrated as Prester John. Whether his embassy stirred the religious zeal or the cupidity of Europe it is difficult to say, but it resulted, whatever its cause may have been, in a Portuguese expedition to the far East, which eventually ended in the leader, De Covilham, marrying and settling in Shoa. I think there is but little need here to repeat the adventures of many European expeditions that were sent at various periods to visit this portion of the globe. Such as refer more immediately to Aden will be found mentioned in the chapter on that possession, while I have elsewhere referred to the “factories” at Mokha.