The Quantum Theory

From the INTRODUCTION.

THE old saying that small causes give rise to great effects has been confirmed more than once in the history of physics. For, very frequently, inconspicuous differences between theory and experiment (which did not, however, escape the vigilant eye of the investigator) have become starting-points of new and important researches.

Out of the well-known Michelson-Morley experiment, which, in spite of the application of the most powerful methods of exact optical measuremen...