310 



CARNEGIE INSTITUTION OF WASHINGTON. 



ABSTRACTS OF PUBLICATIONS AND INVESTIGATIONS. 



Preliminary results of ocean magnetic observations on tlie Carnegie from Washington, 

 D. C, to Dakar, Africa, thence to Buenos Aires, South America, October 

 1919 to January 1920. J. P. Ault. Terr. Mag., vol. 25, 9-13 (Mar. 1920). 



Preliminary results of ocean magnetic observations on the Carnegie from Buenos Aires, 

 South America, to St. Helena, February and March 1920. J. P. Ault. Terr. 

 Mag., vol. 25, 49-52 (June 1920). 



Preliminary results of ocean magnetic observations on the Carnegie from St. Helena to Cape 

 Town, thence to Colombo, Ceylon, April to June 1920. J. P. Ault. Terr. 

 Mag., vol. 25 (September 1920). 



These three papers give the preliminary results of the magnetic observations 

 on the Carnegie during the present cruise (No. VI) from Washington to 

 Colombo, Ceylon, October 1919 to June 1920. Notes on the various passages 

 are also given. 



Table 1 will serve to show the magnitudes of the chart differences as 

 determined from a comparison of the Carnegie observed values of the mag- 

 netic elements with values scaled from the most recent magnetic charts: 

 For declination, U. S. Hydrographic Office No. 2406 for 1920 and British 

 Admiralty No. 3775 for 1917; for inclination, U. S. Hydrographic Office 

 No. 1700 for 1920; and for horizontal intensity, U. S. Hydrographic Office 

 No. 1701 for 1920. The new material for these charts was supplied almost 

 entirely by the Department of Terrestrial Magnetism. 



In order to explain the significance of the letters E, W, N, S as affecting the 

 application of the chart differences, it may be stated that E and N have been 

 treated as being plus, W and S as minus, the chart difference being equal to 

 the Carnegie value minus the chart value. The horizontal intensity is always 

 regarded as positive, and the signs, plus and minus, have their usual 

 significance. 



Table 1. — Range in chart differences. 



lUnits of third decimal C. G. S. 



Preliminary average annual changes of the magnetic elements in the Atlantic Ocean, 

 1909 to 1920. J. P. Ault. 



The annual-change values given in table 2 were obtained by utilizing the 

 results of observations made near the different points of intersection of the 

 Carnegie's several cruises from 1909 to 1920. As it is practically impossible 

 to repeat observations at precisely the same spot, all the values used were 

 compared with the values as shown on the U, S. Hydrographic Office magnetic 

 charts for 1920. The difference in the chart corrections for two groups thus 

 obtained, divided by the time-interval in years, was taken as the average 

 annual change for the mean position of the two groups under consideration. 

 This method is similar to the method of straight-fine interpolation as outUned 



