310 



SCIENCE. 



[N. P. Vol. IX. No. 218. 



year. Added to this, the purely hydro- 

 graphic work has been carried on by a fleet 

 of sixteen vessels, of which ten are steamers. 

 The operations have been widely distribu- 

 ted, extending as far as the Pribilof Islands 

 in the Bering Sea. A longitude determi- 

 nation was made from Sitka, of Kadiak 

 and Unalaska, in which twenty-one chro- 

 nometers were carried on four successive 

 trips. The probable error of the resulting 

 longitudes was 0'.20 for the former and 

 0'.21 for the latter. A tidal indicator, 

 similar to the one in New York, has been 

 erected at Philadelphia, and one is in proc- 

 ess of construction at San Francisco. The 

 mechanism, actuated by the tide, furnishes 

 the navigator at any moment, at a dis- 

 tance of one mile, with necessary informa- 

 tion as to the chai-acter and amount of the 

 tide. 



Among the auxiliarj' duties of the service 

 may be mentioned the establishment of trial 

 speed courses for ships of the Navy (a num- 

 ber of which have been recently laid out) ; 

 the exploration of oyster beds ; the fauna of 

 the Gulf Stream ; the administration of an 

 Office of Standard Weights and Measures, 

 from which prototypes are issued to the dif- 

 ferent States ; meteorological researches for 

 the use of the coast pilot ; the study of as- 

 tronomical refraction ; mathematical inves- 

 tigations on the theory of projections, on 

 the equations of steady motion, on errors of 

 observations ; and finally, in experimental 

 researches in engraving, electrotyping and 

 lithography ; all of which knowledge finds 

 application in the various fields of activity 

 now covered by the Coast and Geodetic 

 Survej^ 



WOEK OF THE "UNITED STATES ENGINEERS. 



Geodetic surveys have also been carried 

 on by the Corps of Engineers of the United 

 States Army. That of the Great Lakes was 

 completed in 1882. The work was reor- 

 ganized in 1892, and resurveys and exten- 



sions thereto are now in progress. Changes 

 in the original plan have been introduced, 

 chiefly in the direction of rapidity of execu- 

 tion. Fewer positions on the circle are now 

 used for horizontal angles, and adjustment 

 is effected by separate small figures, rather 

 than through any extended scheme. In the 

 measure of the Mackinaw base three tapes 

 were used, each a kilometer in length. Each 

 section of the tape was compared with a. 

 standard length of 100 meters established 

 on the ground. This standard length was 

 determined by means of an 8-meter bar 

 packed in ice, which in turn was compared 

 with the Repsold meter, E 1878. 



The Engineer Corps of the Army has 

 also had charge of the Mexican boundary 

 survey, and of the work done by the 

 Missouri and Mississippi Eiver Commis- 

 sions. The report on the Mexican bound- 

 ary is already in type, but is not ready for 

 distribution. 



The Missouri River Commission has 

 completed a triangulation from St. Louis 

 to Three Forks, in Montana, a distance of 

 2,551 miles. The work follows the river 

 and covers the valley from bluff to bluff. 

 Precise levels have been run over 807 miles 

 of it, and ordinary levels cover the remain- 

 der. Ten base lines have been measured 

 with a standardized steel tape. 



The Mississippi River Commission, utiliz- 

 ing some work already done by the Lake 

 Survey and the Coast and Geodetic Survey, 

 has now a complete connection from the 

 Gulf of Mexico to St. Paul, in Minnesota. 

 The total distance is about 1,600 miles. 

 Twenty-seven bases have been used, of 

 which eighteen have been measured by the 

 Commission with a steel tape 300 feet long. 

 The work has been adjusted by quadri- 

 laterals employing the method of least 

 squares. 



E. D. Preston. 



Executive Officer to Supeeintendent 

 U. S. Coast and Geodetic Sukvey. 



