Excerpt from The Earth: Its Shape, Size, Weight and Spin HE aim of this book is to explain in a general way, without mathematical detail, how the shape and size of the Earth have been determined, how its mass has been measured, and how we know that it rotates, and so uniformly that it is a nearly perfect time-keeper. Some account is given of the tidal action which must gradually be reducing the spin, a subject of which our knowledge is chiefly due to the researches of Sir George Darwin. Readers who Wish to study further the matters dealt with here, will find more detailed treatment under various headings in the eleventh edition of the Encyclopaedia Britannica. A bibliography of each subject is there given. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.