PRINCIPLES OF MECHANICS by JOHN L. SYNGE. PREFACE TO THE SECOND EDITION: This edition differs in no essential way from the first. The principal revision occurs in Chap XIII, where the account of the motion of a particle in an electromagnetic field has been completely rewritten. The treatment of principal axes of inertia in Chap XI has been amplified, and some revisions have been made in the treatments of Foucaults pendulum, the spinning projectile, and the gyrocompass. The emphasis on units and dimensions has been increased by the inclusion in the earlier part of the book of a few short paragraphs, with references to the Appendix, where these matters are discussed in detail. A few additional exercises have been inserted, and numerous minor corrections have been made. We wish to thank all those readers who have contributed to the improvement of this second edition by their suggestions, arid, in particular, Professors L. Infeld, A. E. Sehild, and A. Weinstein. JOHN L. SYNGE BYRON A. GRIFFITH PITTSBURGH, PA. TORONTO, ONT. July, 1948. PREFACE TO THE FIRST EDITION: In a sense this is a book for the beginner in mechanics, but in another sense it is not. From the time we make our first move ments, crude ideas on force, mass, and motion take shape in our minds. This body of ideas might be reduced to some order at high school as crude ideas of geometry are reduced to order, but that is not the educational practice in North America. There is rather an accumulation of miscellaneous facts bearing on mechanics, some mathematical and some experimental, until a state is reached where the student is in danger of being repelled by the subject, as a chaotic jumble which is neither mathematics nor physics. This book is intended primarily for students at this stage. The authors ambition is to reveal mechanics as an orderly self contained subject.