Khulusi notes that although the details of scientific pursuits at the time of the Umayyad Caliphate in Damascus are not clear, those of the Abbasids are much more abundant. At the time of the second Abbasid Caliph, Abu Ja'far al-Mansur (d.775), the Academy of Jundeshpur doubled its scientific research activity. It was later joined by another major academic centre, the House of Wisdom in Baghdad, founded by the Caliph Abu Ja'far al-Ma'mun (d.833).