Sir Joseph Norman Lockyer (1836–1920) was one of the pioneers of astronomical spectroscopy and became one of the most influential astronomers of his time. His main interest was sun spectroscopy, which led him to discover helium independently of Pierre Janssen, a scientist who posited its existence in the same year. In addition to his work in astronomy, Lockyer was one of the founders of Nature and was the editor of the journal for its first fifty years. This is the second edition of Lockyer's guide to spectroscopy, first published in 1878. It begins with the basics of spectroscopy such as the physics of waves and the method of observing spectra. Later chapters describe the history of the method and some of Lockyer's own experiments and findings. This book is a fascinating part of the history of astronomy, giving insights into the development of a method vital to the field.