A Treatise on the Adjustment of Observations

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Excerpt from A Treatise on the Adjustment of Observations: With Applications to Geodetic Work and Other Measures of Precision It hence followed as the next great advance that the instrument was made adjustable in most of its parts, so that the relative positions of the parts are under the control of the observer. This is getting to be more and more the case with the better class of instruments. Not only is error diminished by the improved construc tion Of the instrument, but also by more refined methods of handling it. It may be, indeed, that some contrivances beyond those required to make necessary readings for the measure of the quantity in question may be needed. Thus, with a graduated circle regular or periodic errors of gradu ation may be expected. If the angle between two signals were read with a theodolite, the reading on each signal, and consequent value of the angle, would be in¿uenced by the periodic errors of the circle of the instrument. Though a single vernier or microscope would suffice to read the cir cle when the telescope is directed to the signals, yet, as the circle is incapable of adjustment, we can only get rid of the in¿uence of the periodicity by employing a number of ver niers or microscopes placed at equal intervals around the circle. It happens that this same addition of microscopes eliminates eccentricity of the graduated circle as well. 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.