[Illustration: _Wide World Photos._ DR. ALBERT EINSTEIN IN HIS STUDY AT BERLIN.] EASY LESSONS IN EINSTEIN A DISCUSSION OF THE MORE INTELLIGIBLE FEATURES OF THE THEORY OF RELATIVITY BY EDWIN E. SLOSSON, M.S., Ph.D. _Literary Editor of The Independent, Associate in the Columbia School of Journalism. Author of “Great American Universities,” “Major Prophets of To-day,” “Six Major Prophets,” “Creative Chemistry,” etc._ _With an Article by Albert Einstein and a Bibliography_ ILLUSTRATED [Illustration] NEW YORK HARCOURT, BRACE AND HOWE 1920 COPYRIGHT, 1920, BY HARCOURT, BRACE AND HOWE, INC. THE QUINN & BODEN COMPANY RAHWAY, N. J. _Deepest of all illusory Appearances, for hiding Wonder, as for many other ends, are your two grand fundamental world-enveloping Appearances, Space and Time._--CARLYLE. _Henceforth Space in itself and Time in itself sink into mere shadows and only a kind of union of the two can be maintained as self-existent._--MINKOWSKI. A PREFATORIAL DIALOGUE (The Purpose of which is to Prevent the Prospective Reader from buying the Book under False Pretenses) SCENE: A street car in uniform movement of translation in any direction. TIME: The present. _The Reader_: (looking over the top of a morning paper): Here’s something queer--a whole page taken with a new discovery in physics--“Eclipse Observations Confirm Einstein’s Theory of Relativity.” Anything about it in your paper? _The Author_: Yes. Here’s a cartoon on it by McCutcheon. _The Reader_: Must be something to it then. McCutcheon always knows what’s news. (Reads on with audible fragments) “Most sensational discovery in the history of science”--“Greatest achievement of the human intellect”--“Upsets Galileo, Newton, and Euclid”--“Revolution in philosophy and theology.” It looks as though I ought to know something about this, doesn’t it? _The Author_: I think you will have to sometime. And you might as well do it now and get it over with. _The Reader_: (running down the column and hitting the high spots): “Parallel lines meet”--“a man moving with the speed of light never grows old”--“gravitation due to a warp in space”--“length of a measuring stick depends upon direction of its motion”--“mass is latent energy”--“time as a fourth dimension”--why, the man is crazy, isn’t he?