Index of Spectra: Appendix S is a book written by William Marshall Watts and published in 1908. This book is a comprehensive index of spectra, which are the unique patterns of light emitted or absorbed by different types of matter. The book is organized alphabetically by element, and within each element, the spectra are arranged by wavelength. The book includes spectra for a wide range of elements, including hydrogen, helium, carbon, oxygen, and many others. This book is an important resource for scientists and researchers in the fields of chemistry, physics, and astronomy, as it provides a valuable reference for identifying and analyzing spectra. Overall, Index of Spectra: Appendix S is a well-organized and informative resource for anyone interested in the study of spectra.This scarce antiquarian book is a facsimile reprint of the old original and may contain some imperfections such as library marks and notations. Because we believe this work is culturally important, we have made it available as part of our commitment for protecting, preserving, and promoting the world's literature in affordable, high quality, modern editions, that are true to their original work.