Prismatic and Diffraction Spectra

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Excerpt from Prismatic and Diffraction Spectra: Memoirs by Joseph Von Fraunhofer The spectrum of the sun was first observed, in 1666, by Newton, who allowed light coming from a small round open ing in a shutter to pass through a glass prism. This spectrum was most impure and a pure spectrum was not obtained until, in 1802, Wollaston repeated Newton's experiment, replacing the round opening by a slit parallel to the edge of the prism. He observed several dark lines crossing the spectrum, which limit ed, as he thought, the difiercnt spectral colors. His descrip tion of this discovery is given at the end of this volume. Working independently of Wollaston, Fraunhofer, in 1814, rediscovered the lines in the solar spectrum, which now bear his name. He at first used a slit and prism but, later, he dis covered that the same phenomena could be obtained by means of gratings made up of wires or ruled on glass. The papers of Fraunhofer in which he describes these results are printed in full in this volume. The great merit of Fraunhofer's work is the systematic, logical method by which he proceeds from ih vestigation to investigation. 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.