THE SLIDE RULE: A PRACTICAL MANUAL BY CHARLES N. PICKWORTH WHITWORTH SCHOLAR; EDITOR OF “THE MECHANICAL WORLD”; AUTHOR OF “LOGARITHMS FOR BEGINNERS”; “THE INDICATOR: ITS CONSTRUCTION AND APPLICATION”; “THE INDICATOR DIAGRAM: ITS ANALYSIS AND CALCULATION,” ETC. _SEVENTEENTH EDITION_ MANCHESTER: EMMOTT AND CO., LIMITED, 65 KING STREET; NEW YORK: D. VAN NOSTRAND CO., 8 WARREN STREET. LONDON: EMMOTT AND CO., LIMITED, 20 BEDFORD STREET, W.C. AND PITMAN AND SONS, LIMITED, PARKER ST., KINGSWAY, W.C. 2. [_Three Shillings and Sixpence net_] _All rights reserved._ PREFACE TO THE FIFTEENTH EDITION. Several new slide rules for special calculations are described in this edition, and the contents further extended to include a section dealing with screw-cutting gear calculations by the slide rule—an application of the instrument to which attention has been given recently. Mention should be made of the fact that some of the special slide rules described in previous editions are no longer obtainable. As, however, the descriptive notes may be of service to those possessing the instruments, and are, in some measure, of general interest, they have been allowed to remain in the present issue. The author tenders his thanks to the many who have evinced their appreciation of his efforts to popularise the subject; also for the many kind hints and suggestions which he has received from time to time, and with a continuance of which he trusts to be favoured in the future. C. N. P. WITHINGTON, MANCHESTER, _November 1917_. PREFACE TO THE SEVENTEENTH EDITION. The sustained demand for this very successful work having resulted in the early call for a new edition, the opportunity has been taken to introduce descriptions of new slide rules and to effect some slight revisions. C. N. P. WITHINGTON, MANCHESTER, _December 1920_. CONTENTS.