26 CARNEGIE INSTITUTION OF WASHINGTON. 



At the end of the previous fiscal year the Carnegie was en route from the 

 mouth of the Amazon to Rio de Janeiro. After visiting the ports of Rio de 

 Janeiro, Montevideo, Buenos Aires, and Cape Town, she arrived at Colombo, 

 Ceylon, June 7, 1911. Having started on her present circumnavigation cruise 

 June 20, 1910, her arrival at Colombo marked the end, approximately, of the 

 first year out. During this year she traversed upwards of 23,000 nautical 

 miles, measuring magnetic declinations at 252 different points, and dip and 

 intensity at 172 different points at sea. In addition to this work, correspond- 

 ing complete determinations were made on land at seven ports and intercom- 

 parisons of magnetic instruments were made at three ports. 



Unexpectedly large errors have been found almost everywhere, except in 

 the South Atlantic Ocean, in the best compass sailing charts now in use. 

 This is especially the case in the Indian Ocean, for which some recently 

 issued charts are in error as much as 4° to 6° in the "compass variations" 

 assigned. To meet the pressing needs of mariners for more trustworthy 

 charts, the data obtained by the Carnegie are promptly furnished to the hydro- 

 graphic establishments of the world engaged in the publication of magnetic 

 charts. It appears from the investigations of the department that the chief 

 source of the errors in existing charts lies in a lack of knowledge of the secu- 

 lar variation of the magnetic elements. It is worthy of note, also, in this 

 connection that observations of atmospheric electricity and atmospheric 

 refraction have been carried on during this voyage of the Carnegie. The 

 importance of precise navigation in recent times gives special interest to 

 the outstanding uncertainties due to atmospheric refraction. 



Expeditions for land determinations of magnetic data have been made to 

 many countries and to many islands. The most extended of these are that 

 carried out by Mr. Stewart in traversing the length of the Amazon River and 

 that by Mr. Sligh in Asia Minor, Turkey, Arabia, Greece, Tripoli, Tunis, 

 and Algeria. The Director of the department, on his way to meet the Car- 

 negie at Colombo, made observations at Tau Island, of the Samoan Group, 

 on the day of the total solar eclipse, April 28, 191 1 ; and also at six other 

 island stations in the course of his voyage. 



The office work of computation and compilation of results and of the con- 

 struction and testing of instruments has proceeded simultaneously with the 

 operations on land and sea. A complete collection of the data obtained since 

 the establishment of the department, including those of the cruises of the 

 Galilee and Carnegie, will be ready for publication by the end of the present 

 calendar year. Three portable magnetometers have been completed and four 

 others are under construction, while various improvements to instruments 

 and apparatus in use have been made, along with all current repairs, in the 

 construction and repair shop of the department. 



