Preface to First Edition
In this book the main contents of the lectures which I gave at the University of
Berlin during the winter semester 1906–07 are presented. My original intention
was merely to put together in a connected account the results of my own
investigations, begun ten years ago, on the theory of heat radiation; it
soon became evident, however, that it was desirable to include also the
foundation of this theory in the treatment, starting with Kirchhoff’s Law on
emitting and absorbing power; and so I attempted to write a treatise
which should also be capable of serving as an introduction to the study of
the entire theory of radiant heat on a consistent thermodynamic basis.
Accordingly the treatment starts from the simple known experimental laws of
optics and advances, by gradual extension and by the addition of the
results of electrodynamics and thermodynamics, to the problems of the
spectral distribution of energy and of irreversibility. In doing this I have
deviated frequently from the customary methods of treatment, wherever the
matter presented or considerations regarding the form of presentation
seemed to call for it, especially in deriving Kirchhoff’s laws, in calculating
Maxwell’s radiation pressure, in deriving Wien’s displacement law, and
in generalizing it for radiations of any spectral distribution of energy
whatever.
I have at the proper place introduced the results of my own investigations into
the treatment. A list of these has been added at the end of the book to facilitate
comparison and examination as regards special details.
I wish, however, to emphasize here what has been stated more fully in the last
paragraph of this book, namely, that the theory thus developed does not
by any means claim to be perfect or complete, although I believe that
it points out a possible way of accounting for the processes of radiant
energy from the same point of view as for the processes of molecular
motion.