DEPARTMENT OF TERRESTRIAL MAGNETISM. 23I 



to Tahiti, up to September 11, 1912, having been received, they will also be 

 published soon. 



The maximum errors in the charts of the lines of equal magnetic inclina- 

 tion and of equal horizontal intensity were as follows: In the eastern part 

 of the Indian Ocean, 3.5° in magnetic dip and one-thirtieth part in the hori- 

 zontal intensity; in the China Sea, 1.5° in magnetic dip and one-fortieth 

 part in horizontal intensity ; in the Pacific Ocean between Manila and Suva, 

 3.5° in dip and one- fourteenth part in horizontal intensity, and between 

 Suva and Tahiti, nearly 8° in magnetic dip for one of the charts and about 

 one-thirtieth part in horizontal intensity. It should be stated that at the 

 date of the issue of the charts in question neither the results of the Galilee 

 dip and intensity observations nor those of recent Antarctic expeditions 

 were available. 



As the cruise of the Carnegie is arranged so as to intersect the paths of 

 the Galilee and of other previous expeditions as frequently as possible, 

 valuable secular variation data are also being obtained. The generally sys- 

 tematic nature of the chart errors, as above noted, appear in large measure 

 to be due to imperfect knowledge of the corrections which must be applied 

 if past observations are to be brought up to date. 



CONTINUATION OF THE MAGNETIC SURVEY OF LAND AREAS IN REGIONS WHERE 

 THE ACQUIREMENT OF NEW AND ADDITIONAL DATA IS URGENT. 



The work during the present fiscal year has been chiefly in Africa, Asia, 

 Australia, and South America, the details of which will be found on pp. 232 

 to 234. The chief expeditions were led by Dr. C. K. Edmunds in Southern 

 China, Indo-China, and Siam between November 1911 and February 1912; 

 by Mr. E. Kidson in Western and Central Australia, including an overland 

 trip of 1,100 miles by caravan from the railroad terminus, Oodnadatta, in 

 South Australia, to Pine Creek, thence by rail to Port Darwin, on the north 

 coast of Australia ; by Mr. W. H. Sligh in Tripoli, Tunis, Algeria, and Mo- 

 rocco, and from the Canary Islands by small boat along the coast of Rio de 

 Oro and Mauretania to St. Louis, Senegal ; by Mr. D. W. Berky in Morocco, 

 Sierra Leone, and French Guinea (on October 29 a trans-Saharan expedi- 

 tion, in charge of Mr. Berky, accompanied by Mr. H. E. Sawyer, left Biskra, 

 Algiers, for Timbuktu) ; by Mr. J. P. Ault's party in Peru, Bolivia, and 

 Chile. There has now been completed a series of stations across the entire 

 continent of South America, beginning at Para, at the mouth of the Amazon, 

 and extending to the Pacific coast at Callao, Peru, via the Amazon and 

 Ucayali rivers and Lima. 



The total number of land stations at which the three magnetic elements 

 have been determined during the fiscal year will amount to about 235 ; at 

 about one-tenth of these stations more or less complete observations had 

 been made previously, and thus data for secular variation will also be ob- 

 tained. 



