DEPARTMENT OF TERRESTRIAL MAGNETISM. 325 



fact serves to differentiate an eclipse magnetic effect from a general, or terres- 

 trial, effect such as might be associated with sun-spot activity. The difference 

 in Greenwich mean time for the average of the three observatories in Great 

 Britain and the Danish Observatory is 18™, and is in the same direction as 

 the difference in time of the phase of maximum obscuration of the eclipse. 

 The difference in local mean time is l** IG"". When data from stations within 

 the totality belt are available, the difference in time of the magnetic effect 

 may be further investigated. 



The declination bay is not found developed in the same manner at stations 

 outside the zone of visibility of the eclipse. This fact leads to the presumption 

 that it was not an effect due to the disturbance of the magnetic state of the 

 entire Earth, but was more or less restricted approximately to the region in 

 which the eclipse was visible. 



The subject of a possible eclipse magnetic effect is of sufficient theoretical 

 importance to merit further careful investigation. It is hoped that advantage 

 may be taken of the next favorable opportunity, which will occur in the 

 United States during the total solar eclipse of June 8, 1918. 



[Since the publication of the results described above, the magnetic observations, made 

 during the solar ecUpse of August 21, 1914, at the magnetic observatory, De Bilt, Holland, 

 have been received, and the declinations confirm the progression in the times when the 

 marked bay occurred. The lowest part of the bay was at De Bilt at 12'i 09™ Greenwich 

 mean time, thus falling between the times for Kew (12"" 01^) and Rude Skov (12'» 15™), 

 in accordance with the respective times of maximum obsciu"ation at the three stations.] 



Researches of the Department of Terrestrial Magnetism (vol. in): Ocean magnetic obser- 

 vations, 1905-1916, and reports on special researches. L. A. Bauer, W. J. Peters, 

 J. A. Fleming, J. P. Ault, and W. F. G. Swann. Quarto. Carnegie Institution of 

 Washington Publication No. 175 (vol. iii). 1916. 



This volume presents the final results of all magnetic observations made 

 at sea, on the chartered vessel, the Galilee, 1905 to 1908, and on the specially 

 constructed vessel, the Carnegie, 1909 to 1914, as also the results of the shore 

 magnetic observations made in connection with the work of the two vessels. 

 Furthermore there are given the preliminary results of the magnetic obser- 

 vations made on the Carnegie, 1915-1916 (September). The "Tables of 

 Results" contain the values of the magnetic declination, the inclination, 

 and the horizontal intensity of the Earth's magnetic field. For the Galilee 

 ocean-work there are 443 stations and for the Carnegie 2,807, making a total 

 for the two vessels of 3,250 stations. 



After a general introduction and a brief account of previous ocean mag- 

 netic surveys, the magnetic work of each vessel is treated separately. The 

 headings of the main chapters or sections for the Galilee work are : General 

 remarks and description of the Galilee; synopses of the Galilee's cruises, 

 1905-1908; methods of work on the Galilee; magnetic instruments and list of 

 instruments used in the Galilee work; specimens of observations and of com- 

 putations (during swing of vessel and on course); shore magnetic work; 

 determination of geographic position at sea; reduction formulae and deter- 

 mination of constants; ship constants and deviation coefficients; specimen 

 computations of deviation-coefficients; ocean magnetic observations on the 

 Galilee and tables of results, 1905 to 1908; shore magnetic observations for 

 the Galilee work, 1905 to 1908; extracts from Director's instructions for 

 cruises and observational work; extracts from commander's field reports and 

 abstracts of the log of the Galilee ; discussion of alidade corrections for stand- 

 ard compass; and auxiliary observations. 



