Excerpt from A Treatise on Astronomical Spectroscopy Since the first introduction of the spectroscope in scientific research, spectrum analysis proper and spectrum analysis in its astronomical applications have been closely and reciprocally related. The rapid development of spectrum analysis has been largely due to the results it has furnished in the observation of celestial objects, and these same results have been of the greatest importance in Astrophysics. It is therefore surprising that hitherto no text-book has existed for this chief field of spectrum analysis, - astronomical spectroscopy. It is true that there is no lack of popular expositions of this branch, some of them admirable in their way, - we need only recall Schellen's excellent work, - but since they do not go beyond the range of popular comprehension they are suitable neither for the serious study of the subject nor for the use of scientists as hand-books. Kayser's Lehrbuch. der Spectralanalyse deals with the subject in a more scientific way, but it treats of celestial spectroscopy in so brief and incidental a manner that it cannot be regarded as a text-book in this branch of spectroscopy. As the domain of astronomical spectroscopy has so constantly widened, every astrophysicist must have felt the increasing need of a work presenting an exhaustive account of all the modern methods and results of research in this branch of science. This need has been so strongly felt by myself as to impel me to undertake the difficult task of compiling a work of this character. The plan of the book indicates the view by which I have been governed: I have endeavored to satisfy the requirements both of practice and theory, while giving at the same time a record of the results thus far accomplished. I have also thought it desirable that the book should be made useful for practical work and advanced study by the addition of a number of spectroscopic tables and a fairly complete Bibliography. In the statement of the results of the spectroscopic investigations upon the heavenly bodies, reference has not been made to all individual observations or discussions, but a selection has been made of those which were sufficient to represent the present state of our knowledge. In the presentation of these facts I have assumed that the reader has such an acquaintance with the subject as may be gained from a book like Schellen's. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.