DEPARTMENT OF TERRESTRIAL MAGNETISM. 



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are of sufficient amount to require the reissue of magnetic charts, even for 

 purely practical purposes, preferably at intervals not exceeding five years. 

 Judging from past experience, theories of the Earth's magnetism which are 

 advanced without adequate consideration of the conditions which must be 

 fulfilled to account for its continual changes are not likely to prevail. Hence 

 for some time at least and for the benefit of successive generations, we must 

 supplement our studies by continued observation of magnetic and electric 

 fluctuations. 



Important as has been the ocean magnetic work, almost equally so, especially 

 for theoretical studies, have been the results obtained at sea pertaining to 

 atmospheric electricity and atmospheric refraction. The "electric" results, 

 obtained chiefly aboard the Carnegie, will have, it is believed, an important 

 bearing on theories of the origin of atmospheric electricity. 



Table 1 brings up to date the summary of the ocean magnetic work of the Galilee and the 

 Carnegie, 1905-1921. From the bottom row of figures, giving the totals for the cruises of the 

 Galilee and the Carnegie, 1905-1921, 317,054 nautical miles, or 365,103 statute miles, it will 

 be seen that the magnetic observations have been made practically daily throughout the entire 

 period, and that the average distance apart for the various magnetic elements is from 96 to 148 

 nautical miles. A comparison of the separate totals for the Galilee, 63,834 nautical miles, and 

 the Carnegie, 253,220 nautical miles, shows the great improvement resulting when a specially 

 constructed non-magnetic vessel like the Carnegie could be utilized and as the instrumental 

 appliances and observational methods were steadily improved in accordance with experience 

 gained. 



