X RAYS, AN INTRODUCTION TO THE STUDY OF RONTGEN RAYS - 1914 - PREFACE - THIS little book does not profess to be a treatise or handbook on X rays. It aims merely at giving an account of such of the present-day methods and apparatus as appear valuable or novel, and which, in many cases, can only be found scattered throughout many journals it treats critically, and here and there somewhat comprehensively, some of the features which have laid claim to the interests of the writer from time to time i t is concerned to some extent with the development of theory as well as of experiment and it attempts to convey a notion, however dis connect, ed and iU-proportioned, of the historical trend of events from Prof. Rontgens world-famous discovery in 1895 down to the end of the year 1913. The author trusts that the form of the book will be acceptable, not only to the student of physics, but o the man of general scientific interests, and particularly to the members of the medical profession, most of whom are keenly alive to the possibilities of the rays which Rontgen has placed at their service. He is aware from experience as t e h e r and examiner of medical students, at Cambridge and London, of their need of a book on the subject which is neither recondite nor mathematical. To two of his colleagues at the National Physical Laboratory, the writer wishes especially to record his grateful thanks. Mr. E. A. Owen has revised both manuscript and proof, and has co-operated extensively in the treatment of Chapter XII., on the Interference and Reflection of X Rays by Crystals, a section which the writer believes to be the first collected account of this new and fascinating branch of physics. Mr. W. F. Higgins havs given freely and generously of his time and energies, and rendered invaluable aid in all the different stages of the work. He has executed with great care a large proportion of the diagrams, and is responsible for the preparation of the index and some of the more lengthy tables. Sir J. J. Thomson, Prof. Bragg, and Mr. C. T. R. Wilson have kindly given permission to include original photographs. The writers obligations are also due to the Councils of the Royal Society, the-Cambridge Philosophical Society, and the RGntgen Society, the Editor of the Archives of the Riintgen Ray, Messrs. J. and A. Churchill, and Messrs. Taylor and Francis, for the loan of original blocks and to Messrs. F. R. Butt Co., A. C. Cossor, H. W. Cox Co., C. H. F. Muller, Newton Wright, The Sanitas Electrical Co., Schall Son, and Siemens Bros. Co. for various trade blocks. Finally, the author would wish to thank his wife and Mr. J. R. Willis for general criticism, and Mr. A. A. Robb of St. Johns College, Cambridge, for permission to include his verses on Maxwells famous equations and the birth of . an X ray. Mr. Robbs skill in parody is not so well known outside Cambridge as his mathematical researches and the author ventures to hope that the c c Revolution of the Corpuscle, which first saw light in the Post-Prandial Proceedings of the Cavendish Laboratory, will serve to temper the wind of those critics who can see only the numerous shortcomings in the book. The writer will be content if his work can be regarded as one of the many tokens of esteem with which old students of the Cavenciish School of Research have delighted to honour their distinguished professor, Sir J. J. Thomson. G. W. C. K. February 1914. CONTENTS...