Prismatic And Diffraction Spectra eBook

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. 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.