262 CARNEGIE INSTITUTION OF WASHINGTON. 



and Jamestown was left on April 9 and the course set direct for Bahia. 

 En route observations of the magnetic declination were made during 

 a complete swing of the vessel, confirming the absence of possible 

 deviations greater than the error of observation. 



Bahia was reached on April 24. Here extensive intercomparisons 

 were made ashore of all instruments used aboard and, as the Brazilian 

 station at Bahia was no longer suitable for secular variation purposes, 

 a new magnetic station was established on Jaburn Island. Observer 

 Schmitt joined the Carnegie at this port in place of Observer Johnston, 

 who had been assigned to take charge of important land magnetic 

 work in Paraguay, Uruguay, Argentina, and Brazil. Mr. Johnston 

 reof cupied the magnetic station of the United States Coast and 

 Geodetic Survey, established by the Explorer in 1907. 



After completion of the land work, the Carnegie sailed from Bahia 

 on May 19 for St. Helena, following a south and east course to about 

 36° south latitude and 6° west longitude, and sailing thence north to 

 St. Helena, where she anchored in Jamestown harbor June 23. On 

 this passage considerable cloudy and stormy weather was experienced. 

 Complete intercomparisons of all instruments w^ere now made ashore 

 and one magnetic station of the Gauss expedition was reoccupied. 



Leaving Jamestown on July 21, a north-northwest course was fol- 

 lowed to about 30° north latitude and 35° west longitude, and then 

 north-northeast and northeast courses to Falmouth, where the 

 vessel arrived September 12. On August 16 and 18 magnetic obser- 

 vations were obtained on eight equidistant headings of the ship, the 

 previous conclusions regarding absence of appreciable ship deviations 

 being again confirmed. 



During this passage from St. Helena to Falmouth, the Carnegie 

 on August 10 crossed her track of 1909. A comparison of the value of 

 the magnetic declination obtained at the point of intersection, once 

 in 1909 and next in 1913, showed that the north end of the compass 

 needle had shifted westward at an average annual rate of 5 minutes; 

 this is in the right direction to account to some extent for chart errors. 

 A reliable value of the secular change derived from sea observations 

 for an interval of not quite four years can only be obtained by means 

 of the refined methods and instruments in use on the Carnegie. 



At Falmouth, besides the usual shore comparisons of instruments, 

 the stations established by the Carnegie during her first call at this 

 port in October 1909, at Trefusis Point and St. Anthony, were re- 

 occupied for the purpose of determining the secular change in the 

 magnetic elements since 1909. For the same purpose magnetic 

 observations were made at the two nearest stations of the Riicker 

 and Thorpe Magnetic Survey of Great Britain, namely, Truro and 

 Porthallow, thus giving additional data for connecting this admirable 

 land survey with the work of the Carnegie. The Carnegie was also 



