Alcuin made the abbey school into a model of excellence and many students flocked to it. He had many manuscripts copied using outstandingly beautiful calligraphy, the Carolingian minuscule based on round and legible uncial letters. He wrote many letters to his English friends, to Arno, bishop of Salzburg and above all to Charlemagne. These letters (of which 311 are extant) are filled mainly with pious meditations, but they form an important source of information as to the literary and social conditions of the time and are the most reliable authority for the history of humanism during the Carolingian age. Alcuin trained the numerous monks of the abbey in piety, and in the midst of these pursuits, he died.