Book excerpt: Excerpt from Astronomical Papers Prepared for the Use of the American Ephemeris and Nautical Almanac, 1882, Vol. 1 It is well known to all astronomers who have given attention to the subject that meridian observations of the moon and planets are not completely represented by any of the existing tables, and that the deviation of prediction from observation is constantly increasing. It is true that, so far as the current requirements of astronomy are concerned, the state of the case may be considered as not unsatisfactory. Not only may the planets be found and eclipses predicted for many years to come by the present tables, but, with the exception of the moon, there is every reason to suppose that the tabular positions will serve the purposes for which they are immediately re quired in navigation and practical astronomy. But when we take a wider view and consider the general wants of science both now and in the future, we find that in the increasing discordance between theory and observation there is a field which greatly needs to be investigated. If mutual gravitation according to the law of newton is the only cause which changes the motions of the planets, then it is mathematically possible to construct tables which shall represent observations with the last degree of precision and through any period of time. It is quite possible that the discordances alluded to proceed solely from the imperfections in the mathematical theory, and do not indicate any unknown cause affecting the celestial motions. But when we investigate more closely, and seek to ascertain the cause of such discordances, we find a state of things which renders it impossible to draw any definite conclusions respecting the ultimate possibility of rep resenting observations by existing physical and mathematical theories. This state of things has its origin in the comparative brevity of the period during which accurate observations have been made, and in the difficulty of conducting, on a systematic plan, mathematical investigations having in view the perfection of astronomy. 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.