First published in 1922, this book represents the first attempt to popularise the more accessible aspects of Albert Einstein's general theory of relativity. Eschewing the mathematical components that put the theory beyond many people's grasp, the author employs metaphorical examples and thought experiments to convey the fundamental ideas and assertions of one of physics' most famous principles -- which remains the accepted description of gravitation more than a century after its first publication. This book will of interest to students of physics as an introductory basis to aid further study.