613920 SON SIX LECTURES, DELIVERED IN 1868, BEFORE THE SOCIETY OF BY HENRY E. ROSCOE, B.A. PH.D. F.R.S. PROFESSOR OF CHEMISTRY IN OWENS COLLEGE, MANCHESTER. WITH APPENDICES, COLOURED PLATES, AND ILLUSTRATIONS. SECOND EDITION. London: MACMILLAN AND CO. 1870. [The Right of Translation and Reproduction is reserved.] PREFACE TO THE SECOND EDITION. IN In the year which has elapsed since the first publication of these Lectures on Spectrum Analysis, much has been done by the active workers in this branch of science to extend our knowledge, especially concerning the physics of the sun. I have, therefore, found it necessary to rewrite almost the whole of the portion of the book relating to celestial chemistry, introducing into the text the latest discoveries of Huggins, Lockyer, Janssen, and Zöllner, which in the former edition were but imperfectly given. It has also been found expedient to re-arrange the subject-matter of Lectures III. and IV., and to add thereto a short description of investigations in several collateral branches of science. The Appendices have been enriched by abstracts of the original communications made to learned Societies by the investigators themselves. Many new illustrations have been introduced into the text, and no pains have been spared to render the work as complete a record as possible of the present state of the subject. April 1870. H. E. ROSCOE. PREFACE TO THE FIRST EDITION. IN publishing the following Lectures I have endeavoured to preserve the elementary character which they naturally assumed in delivery, thinking it best to give further detail in a series of Appendices. If the book thus assumes less of the character of a complete treatise than might be desirable, it gains in value for the general reader, inasmuch as the science of Spectrum Analysis is at present in such a rapid state of growth that much of the subject is incomplete, and, therefore, necessarily unsuited to the public at large. I hope, however, that the addition of many extracts from the most important Memoirs on the subject may prove interesting to all, as it will certainly be useful to those specially engaged in scientific inquiry, as indicating the habits of exact research and accurate observation by which alone such striking results have been attained. For the permission to reproduce exact copies of Kirchhoff's, Angström's, and Huggins' maps, together with the Tables of the positions of the dark solar and bright |