DEPARTMENT OF TERRESTRIAL MAGNETISM. 331 



an average daily change in the solar constant of 1.5 per cent. Moreover, the 

 reason why the magnetic constant, or the horizontal intensity, is larger, on 

 the average, on the second quiet day, is because, on the average, the solar 

 constant is slightly smaller on the second day than on the first. 



General results of the magnetic survey of the Pacific Ocean. L. A. Bauer and W. J. Peters. 

 Terr. Mag., vol. 20, 95-103 (September 1915). Read at the meeting of the Ameri- 

 can Association for the Advancement of Science, San Francisco, August 4, 1915. 



When the magnetic survey of the ocean areas, by the Carnegie Institution 

 of Washington, was begun at San Francisco, ten years ago, little was known 

 of the magnitude of the errors that were supposed to exist in the magnetic 

 charts covering the high seas, and the Pacific Ocean especially, with the excep- 

 tion of the region covered by the voyage of the Challenger, was nearly a blank 

 as regards magnetic observations. The first magnetic survey of the Pacific 

 Ocean will be completed by the end of 1916. The cruises of the Galilee in this 

 ocean, August 1905 to May 1908, have extended over 61,000 nautical miles; 

 those of the Carnegie, between January 1912 and July 1915 (up to her arrival 

 at Dutch Harbor, Alaska), have covered about 36,900 miles, and they will 

 approximate 75,000 miles by the end of 1916. The aggregate length of the 

 tracks followed by both vessels in the Pacific Ocean, 1905 to 1916, will, accord- 

 ingly, be about 136,000 miles. 



During the decade August 1905 to July 1915, in addition to the observations 

 in the Atlantic and Indian oceans, 689 values of the magnetic declination and 

 578 each of dip and intensity have been observed by the Galilee and the 

 Carnegie in the Pacific Ocean; or, we may say that magnetic observations 

 have been made in the Pacific at stations averaging about 77 miles apart. The 

 many points of intersection serve to correlate the work of the two vessels and 

 to furnish data for the determination of the secular changes. Besides the 

 magnetic observations made at sea, many others were made on land at each 

 port of call, not only to control the constants of the ship's instruments, but 

 also to obtain data for secular change by reoccupying old stations wherever 

 possible, or to establish stations for future use. Valuable instrumental com- 

 parisons were made at the magnetic observatories of Sitka, Honolulu, Zikawei, 

 Tokio, Christchurch, and Apia. 



The magnitude of the corrections to the magnetic charts and their distri- 

 bution is now known in nearly all the oceans. Plate 1 shows the regions of 

 all the largest errors in magnetic decUnation for the Pacific Ocean. In prepar- 

 ing this plate, the declinations were scaled from charts published in 1898 

 (U. S. No. 1700), 1905 (British No. 2598 and German XIV, No. 2), and 1912 

 (British No. 2598), and later editions as they became available during the 

 survey. The corrections are to be added algebraically to the declinations (east 

 declination being considered positive), as scaled from the charts, in order to 

 make them conform to the results from the cruises of the Galilee and Carnegie. 

 It is not possible to differentiate between the British, German, and American 

 charts without adding more figures and thereby losing the salient features of the 

 diagram. Suffice it to say that usually the corrections to the three charts are 

 about of the same order of magnitude and sign, with the one exception in the 

 group just west of the South American coast. In this group the corrections 

 to the British charts were about 1?3 numerically smaller than those of the 

 German and American charts, which are the ones shown in this region. 



It will be seen that all of the large positive corrections are in an area roughly 

 bounded by the one hundred and fiftieth meridian of west longitude, the North 

 American coast, and an imaginary line drawn from Panama to a point in lati- 

 tude 50° south, longitude 150° west. The maximum corrections of over +2° 

 are in the south apex of this triangle. It should, however, be stated that the 



