TERRESTRIAL MAGNETISM 



55 



results of magnetic observations made on Amundsen's Northwest 

 Passage voyage, 1903-1906,^ and by the Swiss expedition to Green- 

 land, 1912-1913, have been published recently.'' 



These new data, approximately corrected for secular change, show 

 that the British Admiralty chart for 1922, the Jones revised polar chart 

 for 1922, and the United States Hydrographic chart (No. 2406) for 

 1925 all indicate too large westerly declinations along the northwest 

 coast of Greenland by about 5° to 10°. For stations along Hudson 

 Strait and the southern part of Baffin Island the charts indicate, in 



general, too small westerly 

 declinations, the difference 

 between observed and 

 chart values reaching at 

 times 10° and averaging 

 about 5°. 



In the region immedi- 

 ately to the north of the 

 north magnetic pole all 

 charts show too large west- 

 erly declinations, on the 

 average about 10°. At Gjoa 

 Harbor, on the southeast- 

 ern side of King William 

 Island, about 130 miles 

 south of the north mag- 

 netic pole, where Amund- 

 sen had in operation a 

 magnetic observatory from 

 November, 1903, to May, 

 1905, the observed mag- 

 netic declination was, on the average, 7.4° West. The three charts 

 mentioned all show east magnetic declination, namely 8° (United 

 States Hydrographic Office), 10° (British Admiralty), and 18° (Jones). 

 On the Arctic drift of the Maud, 1922-1925, observations of the 

 three magnetic elements were made at numerous stations on the ice, 

 sufficiently remote from the ship's influence. Isomagnetic lines 

 (magnetic declination, inclination, and horizontal intensity) have been 

 constructed for the epoch 1925.0 by Dr. H. U. Sverdrup, in charge 

 of the scientific work, for the region north of Bering Strait nearly 

 to the parallel of 75° N. and between the New Siberian Islands and 



sAage Graarud and Nils Russeltvedt: Die erdmagnetischen Beobachtungen der Gjoa-Expedi- 

 tion, 1903-1906, Geofys. Publikaiioner, Vol. 3, No. 8, Oslo, 1925 (abstracted in Terrestr. Magnet, and 

 Atmospher . Electr., Vol. 31, 1926, pp. 17-21). 



6 Alfred de Quervain and P.-L. Mercanton: Ergebnisse der Schweizerischen Gronlandexpedition 

 1912-1913, Neue Denkschr. Schweiz. Nalurforsch. Gesell., Vol. 53. 1920, Zurich; reference on pp. 180- 

 184 (P.-L. Mercanton: Les observations de magnetisme terrestre, abstracted in Terrestr. Magnet. 

 and Atmospher. Electr., Vol. 31, 1926, pp. 15-16). 



Fig. 2 — The lines of equal magnetic declination for 1926 

 from Fig. i without geographical outlines for greater 

 clarity. Scale, 1:75,000,000. The variation is here 

 reckoned 180° east and west, whereas on Fig. i it is 

 reckoned 360° continuouslv from west to east. 



