For more than twenty years, one of us (Bruce Eastwood) has been studying the texts and manuscripts of four Roman works. These are Pliny the Elder's Natural History, Macrobius's Commentary on Cicero's Somnium Scipionis, Martianus Capella's Marriage of Philology and Mercury, and Calcidius's Commentary on the Timaeus of Plato. Manuscripts of these works multiplied during the ninth century, in the culture of the Carolingian renaissance, and each of the works contained or stimulated astronomical diagrams that can reveal to moderns certain concerns of the Carolingian scholars and leaders involved. An important stimulus for the present work was the discovery that early medieval astronomy, especially in the era of Charlemagne and his successors, consisted of texts that went far beyond the boundaries of computus, which modern scholars have long believed to be the only significant context for astronomical studies of that time. It became apparent early that the texts sometimes contained varying or innovative diagrams where no other sign of divergence from the text could be seen. Such diagrams were not necessarily corruptions or errors; they were frequently found to provide indications of understandings of the texts-understandings different from those of modern scholars and generally ignored by editors of the texts. Furthermore the traditions of these diagrams lasted in many cases from the Carolingian era to the fifteenth century.
Over the years Eastwood collected a large number of microfilms of the manuscripts of the four texts and of other texts using any of the planetary diagrams derived from the four Roman texts. He carried out the initial locating and identifying of all the diagrams referred to in the present work. In the summer of 1997 the two of us came together for three months at the Max Planck Institute for History of Science in Berlin to work directly on the present compilation and analysis of the planetary diagrams. In the summer of 1999 we were, again at the Institute in Berlin, able to work together intensively to follow up our basic work of two years earlier. Finally, in the summer of 2001 we completed the scholarly tasks needed for our work. The long preparatory work by Eastwood was supported generously at different times by the National Science Foundation, the Institute for Advanced Study (Princeton), and the American Philosophical Society and by frequent summer research grants from the University of Kentucky. The collaborative stage, from 1997 onward, was generously supported especially by the Max-Planck-Institut-fur-Wissenschaftsgeschichte (Berlin) and by both the Deutsche Akademische Austauschdienst and the National Science Foundation as well as the University of Kentucky. Without these many sources of support over the years this project could never have been completed, and we are extremely grateful to each of these institutions for helping to make this work possible.
Regarding our collaboration, we want to emphasize that although Eastwood contributed the microfilms and the data about the manuscripts and the diagrams, it was the conversations between us primarily during each of the three summer sessions of work together, that produced the final separations and classifications of the individual diagrams. Often it would seem at first to us that a diagram was referring to a doctrine of one author, Martianus Capella for example, when further questioning and analysis would then show us the error of our preliminary assessment and lead us to assign the diagram in question to a doctrine of a different author, Macrobius for example. Correct assignment of a diagram to its originating text was not always obvious or easy, and our give-and-take in discussing such questions has made the final result in this work far superior to what either of us could have accomplished without the other. Finally, the organization of the work in its present form, while requiring consultation between us, is almost completely the contribution of Graßhoff. …