Alchemy in the Middle Ages was therefore a comprehensive field of endeavor concerning itself with every branch of chemical and mineral technology. Although alchemy was known in the West from the mid-twelfth century, serious attempts to assimilate the huge mass of Arabic writings on the subject were not widespread until the first half of the following century. In the mid-thirteenth century, Latin alchemy underwent a new and powerful treatment in On Minerals by Albertus Magnus. The Opus maius, Opus minus, and Opus tertium of Roger Bacon, all composed in the 1260s at the behest of Pope Clement IV, reveal the keen interest of the Franciscan friar in alchemy. The Summa was apparently written in the last third of the thirteenth century, probably by an obscure Franciscan named Paul of Taranto, who is said to have lectured in Assisi. The Summa perfectionis represents the apogee both of alchemy in the high Middle Ages and its interaction with scholasticism.