First published in 1956, this classic work by N.F. Ramsey, 1989 Nobel Laureate in Physics, provides an account of atomic and molecular structure. After an introductory section reviewing experimental apparatus and the kinds of quantities that can be measured, Ramsey provides comprehensive accounts of gas kinetics, chemical equilibria, and atomic and nuclear magnetic moments by nonresonance methods. He also provides tables of nuclear moments, as well as detailed accounts of nuclear and molecular interactions. Finally there are sections on atomic fine and hyperfine structure, and the design of experimental apparatus. The focus throughout is on the physics of beams composed of electrically neutral particles. As a seminal work by one of the world's leading scientists, this volume will interest students and researchers in a range of fields, including atomic physics, physical chemistry, spectroscopy, and biological chemistry.