It was not uncommon in the Middle Ages for a variety of short texts on related themes to be written as separate booklets, and later bound together, or else to be collected up and written out as a group. Sometimes, as in the present case, separate groups of texts are bound together to form a larger group. This volume contains several features pointing to the fact that it was used in Ely in the Middle Ages. The 'Philosophia' (also known as 'De naturis inferiorum et superiorum' or 'About the creation of the world') of the scientist and mathematician Daniel of Morley was an important work which brought Arabic mathematical theory into western thought. Daniel of Morley, who flourished about 1200, left England to study in Toledo, where Arabic texts and teachers were available. On this page, he discusses the orbit of the planets when they appear to go backward (to be in retrograde). The Arabs were knowledgeable about planetary orbits and calculating them because they had to navigate across the desert. The diagram refers to the retrograde phase of Saturn.