In April 1976 I began to see that this book was already begun. I found myself at that time drawing and writing a scatter of sketches and notes that gradually grew. During the years, however, I have never felt that finality was achieved. Even now, as I write no more and delete no more, the work is incomplete. It is no more than the limited remarks that I can make in the complicated circumstances of the wide field of TMM, the Theory of Mechanism and Machines.

I wish to acknowledge the primary influence of the International Federation for the Theory of Mechanisms and Machines. Without IFToMM, without its wide membership among the territories of the world, and without the magnificent opportunity this body has given me to consult with my colleagues in western and eastern Europe, the USSR, India, Asia, and in the Americas, this book would never have been attempted. Let me mention here with gratitude the encouragement and the general assistance I have had from the many individual scientific workers of IFToMM, and from their institutions. It should be needless to say that we (these colleagues and I) collectively encourage the life of IFToMM and trust that that life will continue to flourish.

At home I must mention my special colleague and sometimes collaborator Professor Kenneth Hunt of Monash University at Clayton in Australia. Without reserve – or so it has seemed to me – he and I have exchanged our views and openly expressed our occasional disagreements for a period now extending over twenty years.