Excerpt from Astronomy, Determination of Time, Longitude, Latitude, and Azimuth From time to time during many years publications have been issued describing the. instruments and methods used by the Coast and Geodetic Survey in the determination of time, longitude, latitude, and azimuth. The general aim has been to provide a working manual which would serve as a guide to the observer in the field and the computer in the office in carrying on the astronomic work of the Survey in a systematic maimer. The exhaustion of previous editions and the introduction of new instruments and methods have made necessary the successive editions, in each of which much has been repeated from the preceding one. The edition of the last publication is now exhausted, which gave in one volume descriptions of the instruments and methods, and was entitled "Determination of Time, Longitude, Latitude, and Azimuth." It was published as Appendix No. 7, Report for 1898. The needs of the members of this Survey for a similar manual, and requests for it by others, make it desirable to issue the present and fifth edition. The subject matter includes most of that in the fourth edition, with a number of changes, however. Some of the most important additions to the previous edition are: The determination of time and longitude, using the transit micrometer; the description of the transit micrometer; determination of time with the vertical circle for use in connection with azimuth observations; a description of the method of observing azimuth coincidently with horizontal directions in primary triangulation; an example of the determination of an azimuth in Alaska with a transit equipped with a transit micrometer; examples of the records and computations in the different classes of work, as actually made at present by the Survey; and statements of the field cost of the different classes of work. A number of new illustrations have been added. The writer takes pleasure in acknowledging here his indebtedness to Mr. H. C. Mitchell, Mr. C. R. Duvall, and several other members of the Computing Division who assisted in preparing this edition. The material is principally the work of former Assistant C. A. Schott, who prepared the first three editions, and of former Assistant John F. Hayford, who prepared the fourth edition. It has not been deemed necessary to insert the derivation of formulæ, except in the few rare cases in which such derivation can not be found readily in textbooks on astronomy. For general developments the reader is therefore referred to Chauvenet's Astronomy, to Doolittle's Practical Astronomy, and to Hayford's Geodetic Astronomy. The last-mentioned book and the fourth edition of this publication appeared about the same time, and as they were by the same author it is natural that some of the text is identical in the two. Much of this publication was copied from the fourth edition without change, and some portions are necessarily identical with the corresponding parts of Prof. Hayford's textbook. In addition to this manual on geodetic astronomy, the American Ephemeris and Nautical Almanac for the year of observation will be required in time and azimuth work, and the Boss Preliminary General Catalogue of 6188 stars, together with the Cape Tables, by Finlay, in latitude determinations. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com