This section of MS 17 comprises the following:
The theme of prognostication runs like a subterranean stream beneath MS 17, occasionally breaking the surface of its pages in the form of small but intriguing rivulets. Prognostication is certainly not alien to a computus manuscript: predicting future time is, after all, the very core of the computistical enterprise. Prediction is also a magnet which attracts other types of information into the orbit of computus. A good example of this is medicine, which has a tradition extending back to Antiquity of predicting the outcome of disease on the basis of calculating "critical days". Hence the initial folios of MS 17 contain texts on the "Three Critical Days" and "Three Marvellous Days" (fol. 3v), as well as lunaria and birth prognostics (fol. 4r), and one of the many versions of the Sphere of Life and Death (fol. 8r). The "Egyptian Days" found in this section of the manuscript can also be found as verses attached to the months of the calendar. At the close of the volume, another group of prognostica comprise the sortes sanctorum (fol. 157v-158v), signs of the Last Judgement (fol. 159r) and New Year's Day prognostics (fol. 159r). The collection of prognostic materials found on fols. 40v-41r are devoted to two kinds of divination: Egyptian Days and the Sphere of Life and Death.
This section of MS 17 is wedged between the Cosmography anthology, and the dossier on Mathematics. The insertion seems almost accidental: there was a blank page (40r) between the close of the cosmography and the double-page abacus on fols. 41v-42r, so the scribes filled it up with prognostic material: warnings about perilous calendar days, and diagrams that can be used to divine the future, based on gamatria or calculations based on the numerical value of letters in a word or name. But why choose prognostica to fill this empty space? One possibility is that the exemplar used by the Thorney scriptorium for MS 17's cosmographical anthology closed with prognostica: in the Peterborough computus, MS 17's sibling volume, the Egyptian Days 1 text is written into the margin beside the sygygia elementorum (MS 17 fol. 39v; Peterborough Tiberius fol. 7r), in the same manner as it surrounds the windrose on fol. 40v of MS 17. Moreover, on the following page in the Peterborough computus (Tiberius fol. 7v) is the Sphere of Life and Death in two versions as found on fol. 41v of MS 17. However, the third prognostication diagram is located some distance away in the Peterborough volume (Harley fol. 5r). MS 17 also contains material not found in Peterborough, and vice versa. Nonetheless, it has been persuasively demonstrated by David Juste that these prognostication diagrams were collected and transmitted by Abbo of Fleury 1, so we may confidently conclude that MS 17 and Peterborough, of not copying from one another, were drawing on more than one common Abbonian exemplar.
1 David Juste, "Comput et divination chez Abbon de Fleury," in Oriens-Occidens 2004, 107-114.