Vili
THE QUANTUM
A
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atomicity of electricity, in its dual aspect of positive and nega
tive electrification, has also to be explained; and it may prove
to be the case that these three types of atomicity represent
only different aspects of some fundamental property of the
electromagnetic field.
In this book emphasis has been laid on the magnetic aspect
of the interpretation of the quantum. It is, of course, recognized
that a complete theory must take into account both electric
and magnetic forces; indeed, in the theory of relativity these
become most closely linked together. The genius of Faraday led to
the development of a mode of representing electric and magnetic
fields by physical lines of force, and these may still serve a
useful purpose in forming mental pictures of certain atomic
phenomena, even though we may be driven eventually to employ
the four-dimensional tubes of electro-magnetic force introduced
by Prof. E. T. Whittaker. There is still much for the mathe
matician to accomplish in treating these “ calamoids ” as
quanta.
The greater part of this work is based upon lectures delivered
to advanced students in the University of St. Andrews. This
accounts for the mode of presentation, for the somewhat detailed
description of fundamental principles, and for occasional repeti
tion. I have endeavoured to take a middle course between a
mathematical and a purely descriptive treatment.
I wish to express my thanks to all those who have assisted
me, and in particular to Mr. R. S. Maxwell, Mr. W. G. Robson
and Dr. Ian Sandeman for help in the preparation of the manu
script or in reading the proofs. For permission to reproduce
diagrams, or for the loan of blocks, my thanks are due to the
Royal Society of Edinburgh, the Editor of Nature, the Editors
of the Philosophical Magazine, Mr. C. H. Douglas Clark, Sir
Alfred Ewing, Mr. H. Moore, Prof. Arnold Sommerfeld, and
Drs. Goudsmit and Uhlenbeck. I am indebted to Prof. A.
Fowler for tables showing the arrangement of electrons in atoms.
H. S. A.
The University,
St. Andrews,
January, ig28
ME