Présentation de l'éditeur
I. General principles. Theory of free electrons p1
II. Emission and absorption of heat p68
III. Theory of the Zeeman-effect p98
IV. Propagation of light in a body composed of molecules. Theory of the inverse Zeeman-effect p132
V. Optical phenomena in moving bodies p168
The publication of these lectures, which I delivered in Columbia
University in the spring of 1906, has been unduly delayed, chiefly
on account of my wish to give some further development to the sub-
ject, so as to present it in a connected and fairly complete form;
for this reason I have not refrained from making numerous additions.
Nevertheless there are several highly interesting questions, more or
less belonging to the theory of electrons, which I could but slightly
touch upon. I could no more than allude in a note to Voigt's
Treatise on magneto-optical phenomena, and neither Planck's views
on radiation, nor Einstein's principle of relativity have received an
In one other respect this book will, I fear, be found very deficient.
No space could be spared for a discussion of the different ways in
which the fundamental principles may be established, so that, for in-
stance, there was no opportunity to mention the important share that
has been taken in the development of the theory by L arm or and
It is with great pleasure that I express my thanks to Professor
A. P. Wills for his kindness in reading part of the proofs, and to
the publisher for the care he has bestowed on my work.
Leiden, January 1909.
H. A. Lorentz.