Excerpt from A Treatise on the Principles and Practice of Levelling: Showing Its Application to Purposes of Civil Engineering, Particularly in the Construction of Roads The figure of the earth is not exactly that of a sphere, but of an oblate Spheroid flattened at the poles the length of the equatorial diameter being 7924 miles, and that of the polar diameter 7898 miles. For our present pur pose, it is sufficiently correct to consider it as a Sphere. 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.