Prismatic and Diffraction Spectra

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II. MEMOIRS Br JOSEPH VON FRAUNHOFER

TRANSITED AND EDITED

By J. S. AMES, Ph.D.

HEW YORK AND WSDON

BARPER k BROTHERS PUBLISBESS 1608

HARPER'S SCIENTIFIC MEMOIRS.

EDITED BT

J. S. AMES, Ph.D.,

NOW READY:

THE FREE EXPANSION OP GASES. Memoirs bv Gay-Lnssac, Jonle, and Jonle and Thomson. Iklitor, J. S. Amks, Ph.D., Johns Hopkins University.

PRISMATIC AND DIFFRACTION SPECTRA.

Memoirs by Joseph von Frannhofer. Editor, J. S. Amrs, Ph.D., Jolms Hopkins University.

IS PREPARATION:

RONTGBN RAYS. Memoirs by Rdutgen, Stokes, and J. J. Thomson. Editor, Prof. GKOueifi F. Babkrb, University of Pennsylvania.

THE SECOND LAW OF THERMODYNAMICS.

Memoirs by Carnot, Clausiiis, and Thomson. Editor, Prof. W. F. Mao IK, Princetcm University.

ON THE PROPERTIES OP IONS. Memoirs by Kohlraiisch and Hittorf. Editor, Dr. H. M. Gooi>- wiN, Massachusetts Institute of Technology.

SOLUTIONS. Memoirs by Pfeffer, Van t'Hoff, Raoult. Editor, Dr. H. C. Jones, Jolms Hopkins University.

ON THE LAWS OP GASRS. Memoirs by Boyle, Amagat, Gay-Lii8sac Editor, Prof. Cabl Babus, Brown University.

THE FARADAY AND ZEEMAN EFFECT. Memoirs by Faraday, Kerr, and Zeeman. Editor, Dr. E. P. Lkwis, University of California.

WAVE THEORY OF LIGHT. Menioii-s by Young and Frefinel. .Editor, Prof. Henbv Cuew, Northwestern University.

MKMOIRS CONCERNING THE LAW OF GRAV- ITATION. Editor, Prof. A. S. Maokenzik, Bryn Mawr College.

NEW YORK AND LONDON: HARPER & BROTHERS, PUBLISHERa

Copyright, 1898, by Habpbb & BBornsBa.

All righU rtttrvtd.

^ PREFACE et

H

The spectrum of the sun was first observed, in 1666, by

Newton, who allowed light coming from a small round opening in a shutter to pass through a glass prism. This spectrum was most impure ; and a pure spectrum was not obtained until, f^* in 1802, Wollaston repeated Newton's experiment, replacing the ^" round opening by a slit parallel to the edge of the prism. He fi observed several dark lines crossing the spectrum, which limit-

ed, as he thought, the different spectral colors. His description 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

(J: 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 investigation to investigation.

The most important contributions of Fraunhofer to the science of Spectrum Analysis are :

1. The application of the objective prism to the study of spectra of the sun, the stars, flames, etc.

2. The discovery of the principle of plane gratings.

3. The discussion of the effect upon spectra of

a. Periodic errors in the ruling of gratings.

I. The shape of the groove.

c. The relative widths of opaque and open spaces.

4. The first measurements of the wave-lengths of various solar lines.

noooo

Preface

5. The discovery of the agreement in wave-length of lines in the spectra of flames and of certain stars with those in the solar spectrum.

All modern work in spectroscopy is based upon that of Fraunhofer, and a brief bibliography of the most important contributions is appended to this volume.

GENERAL CONTENTS

PAGE

Preface v

Determination of the Refractive and the Dispersive Power of Different Kinds of Glass with Reference to the Perfecting of Achromatic

Telescopes 1

New Modification of Light by the Reciprocal Influence and Diffraction of the Rays, and the Laws of this Modification 11

Short Account of the Results of New Experiments on the Laws of Light,

and their Theory 39

Biographical Sketch of Fraunhofer 61

WoUaston's Discovery of the Fixed Lines 63

Bibliography 64

Index 67

Determination of the Refractive and the Dispersive

Power of Different Kinds of Glass, with Eeference

TO THE Perfecting of Achromatic Telescopes.

Denkachriften der kdniglichen Akademie der Wissermhaftemu MuTichen, V.,