390 



SCIENCE. 



[N. S. Vol. XXI. No. 532. 



methods and instruments adopted for the sea 

 work, which have thus far proved successful, 

 are described in detail. In a general retro- 

 spective consideration of the work of the past 

 five years it is pointed out that in this period 

 observations have been made at 1,636 stations 

 of which about one eighth are points previously 

 occupied by the survey and since used for 

 observations to secure data for ascertaining 

 the secular change of the magnetic elements. 

 The work in about a dozen states has been 

 practically completed except for special in- 

 vestigations and secular change observations. 

 During the year a bureau of international re- 

 search in terrestrial magnetism has been 

 created by the Carnegie Institution of Wash- 

 ington, with the inspector of the magnetic 

 work of the coast survey in charge as director, 

 and the cooperation thus ensured is certain to 

 prove extremely profitable in results. 



The determination of the longitude of 

 Manila from San Francisco, thus completing 

 the first longitude circuit of the earth, was one 

 of the astronomical events of the year, and in 

 Appendix No. 4 is a comprehensive illustrated 

 report on the various instruments and opera- 

 tions used in the undertaking with a com- 

 parative resume of the various links and re- 

 sults from which the longitude of Manila had 

 been determined from the westward. The 

 generous cooperation of the Commercial Cable 

 Company, through whose patriotic enterprise 

 the work was made feasible, is gratefully ac- 

 knowledged. The results of the determina- 

 tions from the eastward and westward differ 

 only by Os.006 or about 8.8 feet. The other 

 results of this expedition are the determina- 

 tions by the telegraphic method of the longi- 

 tudes of Honolulu, and Midway and Guam 

 Islands. 



The third attempt at representing the tide 

 for the world at large, the first having been 

 made by Whewell and Airy and the second by 

 Berghaus, is described in Appendix No. 5. 

 The advancement in recent years of the gen- 

 eral use of the harmonic analysis and the 

 greatly improved tidal data that are now ob- 

 tainable for such a great part of the globe 

 coordinate to make a new presentation of this 

 subject very opportune. The theoretical dis- 



cussion of the problems involved, the wide 

 range of data and authorities consulted and 

 referred to, the graphic presentation of the 

 cotidal lines, the results presented and the 

 conclusions deduced make a most suggestive 

 paper and one which will be highly interesting 

 to all students of the subject. 



The results of the precise leveling operations 

 for the year are published in Appendices Nos. 

 6 and 7, which submit them in a detail that 

 makes them immediately available for the re- 

 quirements of surveyors and engineers. These 

 extend the precise level net, as previously pub- 

 lished, six hundred miles to the westward, 

 from Red Desert, Wyoming, to Owyhee in east- 

 ern Idaho; and from Holland, Texas, two 

 hundred miles southwest, to Seguin, Texas. 

 An interesting feature is an account of the 

 change in the manner of support for the level- 

 ing rods, with the comparative discussion of 

 the old and the new methods and the conse- 

 quent confirmation of the importance of the 

 new system. 



The account of operations submitted by the 

 assistant in charge gives the story of the work 

 of the various computing, drawing, engraving 

 and chart divisions of the office, in which the 

 results of the field work are discussed or pre- 

 pared for the publications and charts wherein 

 they are placed at the service of the public. 



A full account of the first recording transit 

 micrometer devised for use in the telegraphic 

 longitude determinations of the Coast and 

 Geodetic Survey is submitted in Appendix No. 

 8, with an account of the exhaustive tests it 

 was subjected to and a recapitulation of the 

 results of experience with this form of instru- 

 ment, mainly in Europe, during the last thir- 

 teen years. The results of these experiments 

 indicate that with the transit micrometer the 

 accuracy of telegraphic longitudes may be 

 considerably increased, if desirable, or the 

 present standard of accuracy may be main- 

 tained at much less cost than formerly. 



The results of all triangulation in California 

 south of the latitude of Monterey Bay are 

 printed in the concluding appendix in full, in- 

 cluding descriptions of stations, as well as 

 their latitudes and longitudes and the lengths 

 and azimuths of the lines joining them. In 



