A Treatise on the Theory of Screws

VI PREFACE. instructive developments was not communicated to the Royal Irish Academy until 1890. The twelfth and latest memoir of the series containing the solution of an important problem which had been under consideration for twenty-five years did not appear until 1898. It therefore seemed that the time had now come when an attempt should be made to set forth the Theory of Screws as it stands at present. The present work is the result. I have endeavoured to include in these pages every essential part of the Theory as contained in the twelve memoirs and many other papers. But the whole subject has been revised and rearranged and indeed largely rewritten, many of the earlier parts have been recast with improvements derived from later researches, and I should also add that I have found it necessary to introduce much that has not been previously published. The pleasant duty remains of expressing my thanks for the help that I have received from friends in preparing this book. I have received most useful aid from Prof. W. Burnside, Mr A. Y. G. Campbell, Mr G. Chawner, Mr A. W. Panton, Mr H. W. Richmond, Mr R. Russell, and Dr G. Johnstone Stoney. In the labour of revising the press I have been aided by Mr A. Berry, Mr A. N. Whitehead, and lastly by Professor C. J. Joly, who it will be seen has contributed several valuable notes. Finally, I must express my hearty thanks to the Cambridge Univer- sity Press for the liberality with which they undertook the publication of this book and for the willing consent with which they have met all my wishes. ROBERT S. BALL. Observatory, Cambridge, 17 May, 1900.