From time immemorial Arabia was divided into North and South, not only by the trackless desert (_al-Rub‘ al-Khálí_, the 'Solitary Quarter') which stretches across the peninsula and forms a natural barrier to intercourse, but also by the opposition of two kindred races widely differing in their character and way of life. Whilst the inhabitants of the northern province (the Ḥijáz and the great central highland of Najd) were rude nomads sheltering in 'houses of hair,' and ever shifting to and fro in search of pasture for their camels, the people of Yemen or Arabia Felix are first mentioned in history as the inheritors of an ancient civilisation and as the owners of fabulous wealth--spices, gold and precious stones--which ministered to the luxury of King Solomon. The Bedouins of the North spoke Arabic--that is to say, the language of the Pre-islamic poems and of the Koran--whereas the southerners used a dialect called by Muḥammadans 'Ḥimyarite' and a peculiar script of which the examples known to us have been discovered and deciphered in comparatively recent times. Of these Sabæans--to adopt the designation given to them by Greek and Roman geographers--more will be said presently. The period of their bloom was drawing to a close in the early centuries of our era, and they have faded out of history before 600 A.D., when their northern neighbours first rise into prominence. [Sidenote: Ishmaelites and Yoqṭánids.] It was, no doubt, the consciousness of this racial distinction that caused the view to prevail among Moslem genealogists that the Arabs followed two separate lines of descent from their common ancestor, Sám b. Núḥ (Shem, the son of Noah). As regards those of the North, their derivation from ‘Adnán, a descendant of Ismá‘íl (Ishmael) was universally recognised; those of the South were traced back to Qaḥṭán, whom most genealogists identified with Yoqṭán (Joktan), the son of ‘Ábir (Eber). Under the Yoqṭánids, who are the elder line, we find, together with the Sabæans and Ḥimyarites, several large and powerful tribes--_e.g._, Ṭayyi’, Kinda, and Tanúkh--which had settled in North and Central Arabia long before Islam, and were in no respect distinguishable from the Bedouins of Ishmaelite origin. As to ‘Adnán, his exact genealogy is disputed, but all agree that he was of the posterity of Ismá‘íl (Ishmael), the son of Ibráhím (Abraham) by Hájar (Hagar). The story runs that on the birth of Ismá‘íl God commanded Abraham to journey to Mecca with Hagar and her son and to leave them there. They were seen by some Jurhumites, descendants of Yoqṭán, who took pity on them and resolved to settle beside them. Ismá‘íl grew up with the sons of the strangers, learned to shoot the bow, and spoke their tongue. Then he asked of them in marriage, and they married him to one of their women.[3] The tables on the opposite page show the principal branches of the younger but by far the more important family