The present fifth conference in this series - counting the 1956 conference in Mainz the same way as the "zeroth" symphonies of Beethoven and Bruckner - was held in conjunction with the centennial of the "Convention du Metre" which was signed May 20, 1875 in Paris, Because of this occasion, an extensive honorary committee was appointed: Honorary Committee; Chairman A. Kastler R. C. Barber(M) W. H. Johnson(M) K. Ogata(M) u. Bonse E. R. Cohen(M) Y. Sakurai A. H. Cook J. H. Sanders(M) P, Dean H. H. Staub(M) R. D, Deslattes U. Stille(M) J. V. Dunworth J, Terrien(M) V. I. Goldanskii(M) M. A. Thompson P. Grivet A. H. Wapstra(M) The members (marked M) of the Commission on Atomic Masses and Fundamental Constants of the International Union of Pure and Applied Physics belonged ex officio to this Committee, The Organizing Committee; chairman A, Horsfield H. Capptuller J . E. Faller J . L. Hall B. W. Petley B. N. Taylor was helped by the following two committees: v vi PREFACE Program Committee; chairman A. H. Wapstra c. Audoin W. H. Johnson W. Benenson R. Klapisch E. R. Cohen A. Rytz P. Giacomo J. H. Sanders Local Committee; chairman P. Grivet c. Audoin R. Klapisch N. Elnekave Y. Le Gallic s. Gerstenkorn P. Petit F. Hartmann M.