DEPARTMENT OF TERRESTRIAL MAGNETISM.* 



L. A. Bauer, Director. 

 GENERAL SUMMARY. 



OCEAN MAGNETIC WORK. 



Volume III of the Researches of the Department, entitled "Ocean 

 ^lagnetic Observations, 1905-191 G, and Reports on Special Researches," 

 was issued by the Institution in 1917. The volume consists of 456 

 pages, a frontispiece (view of the Carnegie under sail), 25 plates, and 

 35 text-figures. Reference may be made to that volume for the final 

 results of the entire ocean magnetic work accompUshed during the 

 period 1905-1914, as also for the preliminary results for the period 

 March 1915 to October 1916. Pages 259-264 of this report show the 

 prehminary magnetic results for the period November 1916 to March 

 1917 — that is, for the cruise of the Carnegie from San Francisco to 

 Buenos Aires, where the vessel remained throughout the balance of 

 the fiscal year. 



There are thus now in print, and in form for immediate use by 

 hydrographic establishments, the results of all of the ocean magnetic 

 work for the entire period of 12 years, 1905-1917. Table 1 shows for 

 each cruise of the Galilee and of the Carnegie the number of days at 

 sea^ the length of the cruise in nautical miles, and the number of 

 observed values of the magnetic declination, inclination, and intensity 

 of the Earth's magnetic field for the entire work, 1905-1917 (March). 

 The subsequent colimins give the average time-intervals, as well as 

 the average distances apart, between the observations. The entries 

 in the bottom row of the table summarize the work of the two vessels 

 from August 1905 to March 1917. This table is an extension of 

 table 72, given on page 358 of Volume III mentioned above. The 

 portion added is for the period November 1916 to Mai'ch 1917, San 

 Francisco to Buenos .\ires, the total distance sailed being 14,775 miles, 

 at a daily average of 132 miles for the 112 days at sea, magnetic 

 observations having been made daily (see page 250). 



It will be seen from table 1 that the aggregate length of all ci-uises of 

 the Galilee and of the Carnegie to March 2, 1917, is 239,224 nautical 

 miles, or about 11 times the Earth's circumference. The average 

 time-intervals and average distances apart for the Galilee work have 

 been decreased by about 45 per cent in the Carnegie work. The 

 increased efficiency, or productiveness, has resulted from the fact that 

 the Carnegie is a non-magnetic vessel and because of the steady 



♦Address, Thirty-sixth Street and Broad Branch Road, Washington, D. C. 

 ^In the case of the Galilee work, to the number of days at sea were added the days spent in the 

 harbor-swings. 



249 



