Oman was included in Yemen by these earlier geographers, doubtless from the fact that Arabs from Yemen were its first colonisers; but all that is known with any certainty is that, from the ninth century a.d. a long line of imams ruled over Oman, with their capitals at Nezweh or Rostok, at the foot of Jebel Akhdar. This title, by which the Arab rulers were known, had been conferred on the Arab rulers of Oman for centuries, and signifies a sort of priest-king, like Melchisedek, to whom, curiously enough, is given the same title in the Koran. The election was always by popular acclamation, and inasmuch as the Omani do not recognise the two 'imams' who immediately succeeded Mohammed, but chose their own, they form a separate sect. In olden days the men of Oman were called 'outsiders' by their Mohammedan brethren, because they recognised their own chief solely as the head of their own religion, and are known otherwise as the Ibadiet or Ibadhuyah, followers of Abdullah-bin-Ibadh, as distinct from the Shiahi (Shiites) and Sunni, between which sects the rest of Islam is pretty equally divided. Internecine wars were always rife amongst them; but, at the same time, these early Omani had little or no intercourse with the outer world. Of the internal quarrels of the country, the Omani historian Salid-bin-Ragik has given a detailed account, but for the rest of the world they are of little interest. In those days Oman seems to have had two ports, Sur and Kalhat, on the Indian Ocean, which were more frequented than Maskat. Marco Polo, 1280 a.d., calls the second Calaiati in his 'Journal,' and describes it as 'a large city in a gulf called, also, Calatu,' and the Omani paid tribute to the melek or king of Hormuz for many generations, but with the rise of Maskat, Sur and Kalhat declined. Oman first came into immediate contact with Europeans in the year 1506, when Albuquerque appeared in Maskat harbour bent on his conquest of the Persian Gulf, and with the object, not even yet accomplished, of making a route to India by way of the Euphrates valley. From Albuquerque's 'Commentaries' we get a graphic description of the condition of the country when he reached it. At first the Arabs were inclined to receive the Portuguese without a struggle; but, taking courage from the presence of a large army of Bedouin in the vicinity, they soon showed treacherous intentions towards the invaders, so that the Portuguese admiral determined to attack the town and destroy it, and the commentator states that 'within were burned many provisions, thirty-four ships in all, large and small, many fishing barks, and an arsenal full of every requisite for ship-building.'