Discussions of Ocean Magnetic Work, 1905-16 



427 



V 



Fto. 33. — Showing Corrections of Magnetic-Declination Charts for the Sub-Antarctic Voyage of the Carnegie, 1915-1916. 



(British Admiralty, ; United States Hydrographic Office, ; German Admiralty, .) 



Figure 34 shows the corrections of the various magnetic-declination charts for the 

 portions of the Facijic Ocean at the time of the Carnegie's Cruise II, 1912. Figure 35 

 shows the same for Cruise IV, 1915 and 1916. An inspection of the curves indicates that, 

 as the ocean data obtained aboard the Galilee and the Carnegie became available, improve- 

 ments were made in the magnetic charts issued by the various hydrographic estabUshments. 



CONCERNING CONSTRUCTION OF NEW MAGNETIC CHARTS. 



The construction of the world magnetic charts of the Carnegie Institution of Wash- 

 ington, as based chiefly on the observations of the Department of Terrestrial Magnetism, 

 both on land and sea, is deferred until about 1918. By that time there will be available 

 additional data from the Carnegie in the Atlantic Ocean and from the land observers in 

 various parts of the globe. Secular-variation tables may then be successfully constructed 

 for referring all of the accumulated results to some selected date. 



