The 16th-century English bibliophile, Robert Cotton, sometimes bound together unrelated manuscripts. This one contains a fragment of an early 12th-century English scientific textbook from Peterborough and an 11th-century pontifical (manual of services conducted by a bishop), part of which was probably made in France but to which additions were made at Sherborne Abbey in Dorset. The scientific textbook comes from two types of sources. First, an early medieval natural science tradition began in the treatises of Isidore of Seville and Bede, and was later expanded by Abbo of Fleury, who lived at Ramsey in the 10th century. To this tradition belong diagrams incorporating Christian doctrine into classical theories on the structure of the heavens and earth. A second component is astrological. Monks and churchmen used this textbook in their theological training. Annals in another part of the book giving the death dates of Peterborough abbots and the handwriting's similarity to that of the Peterborough Chronicle (at the Bodleian Library, Oxford) place the manuscript's origin at that monastery. Excerpting Isidore of Seville's 'De natura rerum' ('About the nature of things'), this page has the diagrams that usually accompany Chapter Five of the book. Organising the twelve months in to six pairs, they are meant to relate the lengths of months to each other, to show the harmony of time as well as to accommodate calculations. The larger circle shows the number of hours in each month, dividing them along a diameter determined by the winter and summer solistices. In Isidore's treatise, the diagram illustrates a discussion of lunar months and the Roman kalends (months).