CHAPTER PAGE
Introduction. General and Historical[xi]
I.The Luminiferous Ether and the Modern Theory of Light[1]
II.The Interstellar Ether as a Connecting Medium[13]
III.Influence of Motion on Various Phenomena[29]
IV.Experiments on the Ether[44]
V.Special Experiment on Etherial Viscosity[67]
VI.Etherial Density[80]
VII.Further Explanations Concerning the Density and Energy of the Ether[87]
VIII.Ether and Matter[98]
IX.Strength of the Ether[115]
X.General Theory of Aberration[127]
Appendix 1. On Gravity and Etherial Tension[143]
Appendix 2. Calculations in Connexion with Ether Density[146]
Appendix 3. Fresnel's Law a Special Case of a Universal Potential Function[152]

LIST OF ILLUSTRATIONS

FIG.Illustrations of Aberration.
1.Cannon shots[35]
2.Boats or Waves[36]
3.Lighthouse beams[37]
4.Ray through a moving stratum[40]
5.Wave-fronts in moving medium[41]
6.Normal reflexion in moving medium[43]
Experiments on Ether drift.
7.Interference Kaleidoscope[51]
8.Hoek's experiment[53]
9.Experiment of Mascart and Jamin[54]
10.Diagram of Michelson's experiment[61]
Illustrations of Ether Machine (Lodge).
11.Diagram of course of light[69]
12.General view of whirling part of Ether Machine[72]
13.General view of optical frame[73]
14.Drawing of optical details[74]
15.View of Ether Machine in action[Frontispiece]
16.Appearance of interference bands and micrometer wires[76]
17.Iron mass for magnetisation[77]
18.Appearance of bands[76]
19.Arrangement for electrification[78]

INTRODUCTION

"Ether or Æther (αιθηρ probably from αιθω I burn,) a material substance of a more subtle kind than visible bodies, supposed to exist in those parts of space which are apparently empty."

So begins the article "Ether," written for the ninth edition of the Encyclopædia Britannica, by James Clerk Maxwell.

The derivation of the word seems to indicate some connexion in men's minds with the idea of Fire: the other three "elements," Earth, Water, Air, representing the solid, liquid, and gaseous conditions of ordinary matter respectively. The name Æther suggests a far more subtle or penetrating and ultra-material kind of substance.