I would wish in this, my first book worthy of the name, to acknowledge my indebtedness to those who have inculcated in me whatever grasp of the subject I now possess: to Professor Michael Jaffé of Cambridge who never allowed one to lose sight of the fact that art history is about works of art; to Professor John Shearman, formerly of the Courtauld Institute, who cajoled all his students to adopt more rigorous standards of historical analysis; to Professor Sir Ernst Gombrich of the Warburg Institute, who taught me directly only on one or two brief occasions, but whose example and encouragement have been a source of inspiration. It was Sir Ernst Gombrich's generous loan of a preliminary typescript of his paper on Leonardo's studies of water which was responsible for my embarking upon Leonardo studies in earnest. My earlier education in science was shaped at school by Dennis Clark, a remarkable teacher. That I subsequently failed to learn as much as I should from my scientific instructors at Cambridge was largely my fault not theirs. In my immediate post-student days, I owed the foundation of my career to Professor Anthony Blunt and to the late Professor Andrew McLaren Young. Professor McLaren Young of Glasgow University appointed me to my first established post and encouraged me in every way possible. His successor at Glasgow, Professor Ronald Pickvance, generously promoted and facilitated the sabbatical year without which this book would not have been completed when it was, if at all.
Warm thanks are due to the staff of those institutions in which I have pursued my studies over a number of years. The unique nature of the library of the Warburg Institute gave feasibility to my programme of research, and the unrivalled accessibility of its holdings saved more hours than I care to think of wasting. The Milanese libraries each made significant contributions in their different ways: the Biblioteca Ambrosiana, with its determinedly archaic air of punctiliousness; the Biblioteca Trivulziana within the efficient and friendly Archivio di Stato; and the Raccolta Vinciana, a working collection for students. Nearer home I have benefited enormously from the collection of Leonardo literature in the National Library of Scotland, presented in memory of the Rev. Alexander MacCurdy. Numerous individuals have made contributions to the furtherance of my research and publications on Leonardo and related topics in the Renaissance. If I specifically mention Professor James Ackerman, Michael Baxandall, Allan Braham, Cecil Clough, Caroline Elam, Robert Gibbs, Richard