CONTENTS. 



CHAP. PAOE 



J. INTRODUCTORY KEPLER, NEWTON, WOLLASTON, 1600-1802 . . 1 



II. FRAUNHOFER, 1814 13 



III. THE FIRST GLIMPSES OF " BRIGHT LINE SPECTRA" 23 



IV. BREWSTER, HERSCHEL, AND FORBES ; BECQUEREL AND DRAPER, 



1822-1843 34 



V. THE FRAUNHOFER LINES EXPLAINED 49 



VI. KIRCHHOFF'S MAP AND WORK 69 



VII. THE WORK OF ANGSTROM AND THALEN 83 



VIII. A NEW METHOD OF WORK 94 



IX. MORE RESULTS OF THE NEW METHOD 106 



X. PRELIMINARY SEARCH AFTER EXPLANATIONS 126 



XI. THE NEW METHOD APPLIED TO LABORATORY WORK 139 



XII. SOME RESULTS OF THE " LONG AND SHORT " METHOD . . . 150 



XIII. DIFFICULTIES 161 



XIV. DETAILS OF SOME OF THE DIFFICULTIES 182 



XV. A POSSIBLE WAY OUT OF THEM . 199 



XVI. INTRODUCTION OF PHOTOGRAPHY 209 



XVII. A STUDY OF THE PURIFIED SPECTRA 229 



XVIII. DISCUSSION OF THE DISSOCIATION HYPOTHESIS 237 



XIX. DISCUSSION OF THE DISSOCIATION HYPOTHESIS (continued] . . . 259 



XX. SOME TEST EXPERIMENTS ABSORPTION PHENOMENA . . . . . 273 



XXI, SOME TEST EXPERIMENTS TRIAL OF NEW METHODS .... 290 



