||The purpose of this volume is to describe the revolution in physics which took place in the first quarter of the twentieth century, and which included the discoveries of Special Relativity, the older Quantum Theory, General Relativity, Matrix Mechanics and Wave Mechanics.
My original intention was to give an account of the history from 1900 to 1950 in a single volume ; but the wealth of material made this undesirable ; and the period from 1926 to 1950 must be reserved for a third book.
I am greatly indebted to Dr E. T. Copson, Regius Professor
of Mathematics in the University of St Andrews, and Dr
J. M. Whittaker, Vice-Chancellor of the University of Sheffield,
for reading the proofs.