skilled in geometry, ingenious devices ( lival), music and astronomy. According to Ibn al-Nad m and Ibn Khallikan their weakest subject was astronamy, but this seems to conflict with the opinions of Ibn Yunus and al-BIrun , hoth good judges, who spoke highly of the accuracy of the Banu Musa's astronomical observations. Mul)ammad, who was the most influential of the brothers, specialised in gcomctry and astronomy, and excellcd Al)mad in all the sciences except in the construction of ingenious devices. AI-l: Iasan was a brilliant geometrician with aretenlive memoryand great powers of deduction....