Excerpt from Researches in Physical Optics, Vol. 2: Resonance Radiation and Resonance Spectra HE researches described in the following pages were made by Professor Wood, in several cases together with collaborators, while he was Ernest Kempton Adams Fellow of Columbia University in 1912 - 1914, and subsequently. In this work, Part II of these Researches in Physical Optics, the important field of investigation opened by the author has been developed in the direction of more detailed study of resonance radiation and resonance spectra. 0 Publication has been delayed from time to time, in order to include new material and, more recently, on account of conditions arising from the war. In the absence in Europe of the author as the volume goes to press, the editors of the series venture to express for the author his-obligation and thanks to his several collaborators and to all who have assisted in his work. To the Astrophysical Journal thanks are due for cuts used in illustrating the fifth paper. 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.