1. The Persian Ibn Khurdádbih (first half of ninth century) was postmaster in the province of Jibál, the Media of the ancients. His _Kitábu ’l-Masálik wa-’l-Mamálik_ ('Book of the Roads and Countries'), an official guide-book, is the oldest geographical work in Arabic that has come down to us. [Sidenote: Iṣṭakhrí and Ibn Ḥawqal.] 2. Abú Isḥáq al-Fárisí a native of Persepolis (Iṣṭakhr)--on this account he is known as Iṣṭakhrí--wrote a book called _Masáliku ’l-Mamálik_ ('Routes of the Provinces'), which was afterwards revised and enlarged by Ibn Ḥawqal. Both works belong to the second half of the tenth century and contain "a careful description of each province in turn of the Muslim Empire, with the chief cities and notable places." [Sidenote: Muqaddasí.] 3. Al-Muqaddasí (or al-Maqdisí), _i.e._, 'the native of the Holy City', was born at Jerusalem in 946 A.D. In his delightful book entitled _Aḥsanu ’l-Taqásím fí ma‘rifati ’l-Aqálím_ he has gathered up the fruits of twenty years' travelling through the dominions of the Caliphate. [Sidenote: Yáqút.] 4. Omitting the Spanish Arabs, Bakrí, Idrísí, and Ibn Jubayr, all of whom flourished in the eleventh century, we come to the greatest of Moslem geographers, Yáqút b. ‘Abdalláh (1179-1229 A.D.). A Greek by birth, he was enslaved in his childhood and sold to a merchant of Baghdád. His master gave him a good education and frequently sent him on trading expeditions to the Persian Gulf and elsewhere. After being enfranchised in consequence of a quarrel with his benefactor, he supported himself by copying and selling manuscripts. In 1219-1220 A.D. he encountered the Tartars, who had invaded Khwárizm, and "fled as naked as when he shall be raised from the dust of the grave on the day of the resurrection." Further details of his adventurous life are recorded in the interesting notice by Ibn Khallikán.[675] His great Geographical Dictionary (_Mu‘jamu ’l-Buldán_) has been edited in six volumes by Wüstenfeld (Leipzig, 1866), and is described by Mr. Le Strange as "a storehouse of geographical information, the value of which it would be impossible to over-estimate." We possess a useful epitome of it, made about a century later, viz., the _Maráṣidu ’l-Iṭṭilá‘_. Among the few other extant works of Yáqút, attention maybe called to the _Mushtarik_--a lexicon of places bearing the same name--and the _Mu‘jamu ’l-Udabá_, or 'Dictionary of Littérateurs,' which has been edited by Professor Margoliouth for the Trustees of the Gibb Memorial Fund. [Sidenote: The foreign sciences.] [Sidenote: Translations from the Greek.] [Sidenote: Ma’mún's encouragement of the New Learning.]