Excerpt from Text-Book on Geodesy and Least Squares: Prepared for the Use of Civil Engineering Students The arc measured by Snellius Of Holland in 1615, it being the first in which the principle of triangulation was employed. He used 33 triangles; measured his base line with a chain, his angles with a sector having sights attached; and found a meridional arc of about 1 His computed circumference was too small. The introduction of cross hairs in the telescope, and its adapta tion to angle instruments, by Picard in 1669. He extended a triangulation over an arc of about 1 23' from a base line nearly seven miles long, and, derived the most accurate degree length thus far given. His angles were carefully measured with a sector Of 10 feet radius, to which a telescope was attached. The facts reported by Richer, on his return from an astronomical expedition in 1672, namely, that his clock, which beat seconds at Paris before starting, lost about two minutes per day while at the island of Cayenne, South America, and could only be corrected by shortening the pendulum li Paris lines. 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.