Persia, which, after the downfall of the Abbasid Caliphate formed the nerve centre of Islamic learning, produced some of the greatest intellectuals of mediaeval times. Great advances were made in almost all branches of knowledge. One of the most outstanding intellectuals of Islam was Abu Rehan Beruni (973--1048 A.D.) who graced the literary meetings of Mahmud Ghaznaui. "Few know physics and metaphysics" says J. N. Sircar, the celebrated Indian historian, "amongst those few the greatest in Asia was Al-Beruni, at once a philosopher and a scientist and preeminent in both of these two seemingly incompatible fields".' Al-Beruni was a distinguished and original scholar of astronomy and other sciences. His Al-Qanun al-Masudi written for his patron Sultan Masud of Ghazni in 1030 A.D. is an astronomical encyclopaedia. A short catechism of geometry, arithmetic, astronomy and astrology ... written in 1030 A.D. and entitled Al-Tahfin li-awail sinaat al-l\rajum deals chiefly with the calenders and eras of ancient peoples.