INTRODUCTION. 



This publication is the third of the series by the Department of Terrestrial 

 Magnetism of the Carnegie Institution of Washington, bearing the general title 

 "Researches of the Department of Terrestrial Magnetism." Each volume has a 

 subtitle setting forth briefly its special contents. Thus the first volume, here 

 designated as Volume I and entitled "Land Magnetic Observations, 1905-1910," 

 contains the results of all magnetic observations made on land by the Department 

 from the beginning of its observational work in February 1905 to the end of Decem- 

 ber 1910. Volume II, "Land Magnetic Observations, 1911-1913, and Reports on 

 Special Researches," contains the results of all magnetic observations made on land 

 during the three years, January 1, 1911, to December 31, 1913. The titles of the 

 special reports in that volume are: Research Buildings of Department of Terrestrial 

 Magnetism; Magnetic Inspection Trip and Observations during Total Solar Echpse 

 of April 28, 1911, at Manua, Samoa; Results of Comparisons of Magnetic Stan- 

 dards, 1905-1914. 



The present volume, No. Ill, on "Ocean Magnetic Observations, 1905-1916, 

 and Reports on Special Researches," contains the final results of the ocean magnetic 

 observations made aboard the Galilee in the Pacific Ocean, 1905-1908, and aboard 

 the Carnegie in the Atlantic, Indian, and Pacific Oceans, 1909-1914, together with 

 preliminary results of the observations on the 1915-1916 portion of the Carnegie's 

 present cruise (No. IV). The special reports relate to auxiliary observations made 

 aboard these vessels, or to special investigations. 



As director, I desire to take this occasion to express my sincere appreciation 

 and deep sense of obUgation to those who have creditably and successfully dis- 

 charged the arduous and responsible duties of commander of vessel, as also to the 

 observers and computers, whose devotion and unflagging interest have made pos- 

 sible the accumulation of the mass of scientific data presented in this volume. 



PREVIOUS OCEAN MAGNETIC SURVEYS. 



The first attempt at an ocean magnetic survey was made, under the auspices 

 of the British government, by the noted astronomer Edmund Halley, between 1698 

 and 1700. He was placed by King George III in command of the saihng ship. 

 Paramour Pink, for "proceeding with her on an expedition to improve the longitude 

 and the variations of the compass." With this vessel Halley made several voyages 

 in the North and South Atlantic Oceans, penetrating to the parallel 52° south. 

 Only the magnetic declination was determined, since at that time instruments for 

 measuring dip and intensity at sea had not been devised. He embodied the results 

 of his observations on a chart of the "Lines of Equal Magnetic Variation," for 

 the year 1700, which method of portraying the distribution of the magnetic elements 

 was first successfully introduced by him.' 



'For furtlier information, reference may be made to the articles by L. A. Bauer, J. P. Ault. and W. F. Wallis. Terres- 

 trial Magnetism and Atmospheric Electricity, vol. 18, 113-132, 1913. 



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