Chapter I: Preface: To Second Edition

The preparation of this new edition has made it possible to correct errors, to further amplify certain portions of the text and to enlarge the ever-increasing bibliography on the subject. Photographs of Professors J. J. Thomson, Michelson, Minkowski and Lorentz are also new features in this edition.

The explanatory notes and articles in the Appendix will, I believe, present no difficulties to readers who have mastered the contents of the book. They are in fact "popular expositions" of various phases of the Einstein theory; but experience has shown that even "popular expositions" of the theory need further "popular introductions."

I wish to take this opportunity of thanking Prof. Einstein, Prof. A. A. Michelson of the University of Chicago, Prof. J. S. Ames of Johns Hopkins University, and Professor G. B. Pegram of Columbia University for help in various ways which they were good enough to extend to me. Prof. J. S. Ames and the editor of Science have been kind enough to allow me to reprint the former's excellent presidential address on Einstein's theory, delivered before the members of the American Physical Society.

B. H.

TABLE OF CONTENTS

PAGE

I. Newton 1
II. The Ether and Its Consequences 27
III. Einstein 41
IV. Appendix 81

Time, Space and Gravitation, by Prof. Einstein 88
Einstein's Law of Gravitation, by Prof. J. S. Ames 93
The Deflection of light by Gravitation and the
Einstein Theory of Relativity, by Sir Frank Dyson,
Prof. A. S. Eddington and Sir J. J. Thomson 112

NEWTON

"Newton was the greatest genius that ever existed."--Lagrange, one of the greatest of French mathematicians.

"The efforts of the great philosopher were always superhuman; the questions which he did not solve were incapable of solution in his time."--Arago, famous French astronomer.

EINSTEIN

"This is the most important result obtained in connection with the theory of gravitation since Newton's day. Einstein's reasoning is the result of one of the highest achievements of human thought."--Sir J. J. Thomson, president of the British Royal Society and professor of physics at the University of Cambridge.

"It surpasses in boldness everything previously suggested in speculative natural philosophy and even in the philosophical theories of knowledge. The revolution introduced into the physical conceptions of the world is only to be compared in extent and depth with that brought about by the introduction of the Copernican system of the universe."--Prof. Max Planck, professor of physics at the University of Berlin and winner of the Nobel Prize.