In laying down a set of general principles to govern the award of the prize, one of the first things considered by the Judges was the relative importance of the Special and the General Theories. It was their opinion that no essay could possibly qualify for the prize which did not very distinctly give to the General Theory the center of the stage; and that in fact discussion of the Special Theory was pertinent only so long as it contributed, in proportion to the space assigned it, to the attack upon the main subject. The same principle has been employed in selecting essays for complete or substantially complete reproduction in this volume. Writers who dealt with the Special Theory in any other sense than as a preliminary step toward the General Theory have been relegated to the introductory chapters, where such excerpts from their work have been used as were found usable. The distinction of publication under name and title is reserved for those who wrote consistently and specifically upon the larger subject--with the one exception of Dr. Russell, whose exposition of the Special Theory is so far the best of those submitted and at the same time so distinctive that we have concluded it will appear to better advantage by itself than as a part of Chapters III. and IV.

Following after Mr. Bolton's essay we have tried to arrange the various contributions, not at all in any order of merit, but in the order that will make connected reading of the book most nearly possible and profitable. Each essay should be made easier of reading by the examination of those preceding it; at the same time each, by the choice of ground covered and by the emphasis on points not brought out sharply by its predecessors, should throw new light upon these predecessors.

The reader will find that no two of the essays given thus in full duplicate or even come close to duplicating one another. They have of course been selected with this in view; each represents the best of several essays of substantially the same character. Not all of them require comment here, but concerning some of them a word may well be said.

Mr. Francis, we believe, has succeeded in packing more substance into his 3,000 words than any other competitor. Mr. Elliot has come closer than anybody else to really explaining relativity in terms familiar to everybody, without asking the reader to enlarge his vocabulary and with a minimum demand so far as enlarging his mental outlook is concerned. Were it not for certain conspicuous defects, his essay would probably have taken the prize. In justice to the Judges, we should state that we have taken the liberty of eliminating Mr. Elliot's concluding paragraph, which was the most objectionable feature of his essay.

Dr. Dushman chose for his title the one which we adopted for this book. It became necessary, therefore, for us to find a new title for his essay; aside from this instance, the main titles appearing at the heads of the various complete essays are those of the authors. The subtitles have in practically every instance been supplied editorially.

Dr. Pickering submitted two essays, one written from the viewpoint of the physicist, the other from that of the astronomer. To make each complete, he naturally found it necessary to duplicate between them certain introductory and general material. We have run the two essays together into a single narrative, with the elimination of this duplicated material; aside from this blue-penciling no alteration has been made in Dr. Pickering's text. This text however served as the basis of blue-penciling that of several other contestants, as indicated in the foot notes.

For the reader who is qualified or who can qualify to understand it, Dr. Murnaghan's essay is perhaps the most illuminating of all. Even the reader who does not understand it all will realize that its author brings to the subject a freshness of viewpoint and an originality of treatment which are rather lacking in some of the published essays, and which it will readily be understood were conspicuously lacking in a good many of the unpublished ones. Dr. Murnaghan of all the competitors has come closest to making a contribution to science as well as to the semi-popular literature of science.

In the composite chapters, the brackets followed by reference numbers have been used as the most practicable means of identifying the various individual contributions. We believe that this part of the text can be read without allowing the frequent occurrence of these symbols to distract the eye. As to the references themselves, the asterisk marks the contributions of the Editor. The numbers are those attached to the essays in order of and at the time of their receipt; it has been more convenient to use these than to assign consecutive numbers to the quoted essays. The several numbers identify passages from the essays of the following contestants:

10: Frederick W. Shurlock, Derby, England. 18: L. L. Whyte, Cambridge, England. 24: Prof. Moritz Schlick, University of Rostock, Germany. 30: C. E. Rose, M.E., Little Rock, Ark. 33: H. Gartelmann, Bremen, Germany. 35: Prof. Joseph S. Ames, Johns Hopkins University, Baltimore. 47: James O. G. Gibbons, East Orange. N. J. 82: Charles H. Burr, Philadelphia. 101: L. F. H. de Miffonis. B.A., C.E., Ottawa, Canada. 102: Charles A. Brunn, Kansas City. 106: J. Elias Fries, Fellow A.I.E.E., Birmingham, Ala. 114: Dean W. P. Graham, Syracuse University, Syracuse, N. Y. 115: Rev. George Thomas Manley, London. 116: Prof. J. A. Schouten, Delft, Netherlands. 121: Elwyn F. Burrill, Berkeley, Cal. 125: Dorothy Burr, Bryn Mawr, Pa. 130: C. W. Kanolt, Bureau of Standards, Washington. 135: Robert Stevenson, New York. 139: Leopold Schorsch, New York. 141: Dr. M. C. Mott-Smith, Los Angeles, Calif. 147: Edward A. Clarke, Columbus, O. 149: Edward A. Partridge, Philadelphia. 150: Col. John Millis, U. S. A., Chicago. 152: George F. Marsteller, Detroit. 156: D. B. Hall, Cincinnati. 165: Francis Farquhar, York, Pa. 178: Dr. George de Bothezat, Dayton, O. 179: Professor A. E. Caswell, University of Oregon, Eugene, Ore. 182: C. E. Dimick, New London, Conn. 186: Earl R. Evans, Washington, D. C. 188: Norman E. Gilbert, Dartmouth College, Hanover, N. H. 192: A. d'Abro. New York. 194: L. M. Alexander, Cincinnati. 197: Kenneth W. Reed, East Cleveland, O. 198: Prof. E. N. da C. Andrade, Ordnance College, Woolwich, England. 216: Professor Andrew H. Patterson, University of North Carolina, Chapel Hill, N. C. 220: Prof. Arthur Gordon Webster, Clark College, Worcester, Mass. 221: Walter van B. Roberts, Princeton University, N. J. 223: Paul M. Batchelder, Austin, Tex. 227: Prof. R. W. Wood, Johns Hopkins University, Baltimore. 229: E. P. Fairbairn, M.C., B.Sc., Glasgow. 231: R. F. Deimel, Hoboken, N. J. 232: Lieut. W. Mark Angus, U. S. N., Philadelphia. 235: Edward Adams Richardson, Kansas City. 263: Prof. William Benjamin Smith, Tulane University, New Orleans. 264: James Rice, University of London, London. 267: William Hemmenway Pratt, Lynn, Mass. 272: R. Bruce Lindsay, New Bedford, Mass. 283: Frank E. Law, Montclair, N. J.

In addition to the specific credit given by these references for specifically quoted passages, the Editor feels that he ought to acknowledge his general indebtedness to the competing essayists, collectively, for the many ideas which he has taken away from their text to clothe in his own words. This does not mean that the Editor has undertaken generally to improve upon the language of the competitors, but merely that the reading of all their essays has given him many ideas of such complex origin that he could not assign credit if he would.

TABLE OF CONTENTS

I.--The Einstein $5,000 Prize: How the Contest Came to be Held, and Some of the Details of Its Conduct. By the Editor 1

II.--The World--And Us: An Introductory Discussion of the Philosophy of Relativity, and of the Mechanism of our Contact with Time and Space. By various contributors and the Editor 19

III.--The Relativity of Uniform Motion: Classical Ideas on the Subject; the Ether and the Apparent Possibility of Absolute Motion; the Michelson-Morley Experiment and the Final Negation of this possibility. By various contributors and the Editor 47

IV.--The Special Theory of Relativity: What Einstein's Study of Uniform Motion Tells Us About Time and Space and the Nature of the External Reality. By various contributors and the Editor 76

V.--That Parallel Postulate: Modern Geometric Methods; the Dividing Line Between Euclidean and Non-Euclidean; and the Significance of the Latter. By the Editor 111

VI.--The Space-Time Continuum: Minkowski's World of Events, and the Way in Which It Fits Into Einstein's Structure. By the Editor and a few contributors 141

VII.--Relativity: The Winning Essay in the Contest for the Eugene Higgins $5,000 Prize. By Lyndon Bolton, British Patent Office, London 169