APPENDIX. TABLE I.-Mean Refractions.. TABLE IJ.-Corrections for Curvature and Refraction. TABLE III.-Elongations and Culminations of Polaris. TABLE V. Reductions for Inclined Stadia Readings. TABLE VI.-Mean Refractions in Declination... TABLE VII.-Pole Distance of Polaris..... 2. For Converting U. S. Weights and Measures. 3. Values of Reciprocals, Squares, etc.. 7. Natural Sines and Cosines.. Conversion of English and Metric Units POCKET IN BACK COVER: GETTYSBURG MAP; ROAD SKETCH AND REPORT; POSITION SKETCH AND Report. CHAPTER I. GENERAL PRINCIPLES. MILITARY TOPOGRAPHY is the determination and representation, by conventional signs and symbols, of such forms and features of a limited portion of the earth's surface as have special reference to its adaptability for military purposes. It includes undulations and accidents of ground, steepness of slopes, relative heights of commanding points, and all occurring incidents of water; the natural growths and character of ground, as forests, prairies, and desert lands; the features of culture and artificial structures of mankind, as crops, groves, canals, railways, roads, bridges, houses, etc., the whole forming a complete and useful picture. The distinguishing characteristic of topography is the graphical representation, on a plane surface, of relative elevations and depressions, as they would appear to an observer looking vertically down from points above the plane. Topography comprises so much of art that the question of personality enters largely into the facility of expressing it, and topographic surveys involve such varied processes, that it is difficult to make hard-and-fast rules to govern them. It has been said by one of the most distinguished scientists of our country, "that while but little more could be done to perfect the principles of other departments of mathematical science, topography was still susceptible of development and improvement." Each topographic position presents a problem as varied and often as difficult of solution as the phases of nature with which it has to deal. |