Excerpt from Methods and Results: Secular Variation of the Magnetic Declination in the United States and at Some Foreign Stations, Appendix No. 12, Report for 1886The practical nature of the inquiry, and the necessity of looking to the publications of the Coast and Geodetic Survey to supply the latest information on the subject of the changes, secular and otherwise, of the direction of the magnetic needle, has caused an ever-increasing demand for these investigations of the survey, and this has acted again as a stimulus to advance our knowl edge Of the secular changes of the magnetic force, both for direction and intensity. It thus becomes necessary every few years to re-discuss or submit to analysis any additional observations, as well as to direct such observations to be made at those places where they may contribute most, effectively towards the elucidation of the laws of change.Appendix No. 6, Coast and Geodetic Survey Report for 1885, contains an exhaustive article on the secular change of the magnetic dip and the magnetic intensity, as observed in the United States from the earliest to the present time. It is accompanied by three maps, showing the actual! Distribution of these magnetic elements for the epoch 1885-0 This, together with the present communication, completes the inquiry in this branch of knowledge by bringing it up to date.During the five years which have elapsed since the last issue of this paper the available material for the discussion of the secular variation of the declination has greatly increased, bring: ing up the number of stations contained in this edition to 94 and the number of declinations to 1071, for each of which full reference is given, as well as a comparison of the observed and com pated values. The average number of observations for a station is 11. It is satisfactory to remark that this increase of observations was found greatly to improve the values of the analytical expres sions, giving greater accuracy to the results deduced and tending to greater uniformity in such phases of the secular variation as the amplitude of the motion and the epochs of maxima and minima or times of magnetic elongation, all of which depend on the geographical position of the stations.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis 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.