294 CARNEGIE INSTITUTION OF WASHINGTON. 



scheme might usefully be arranged whereby anyone desiring such copies could secure them 

 from certain observatories for a prearranged fee. As a preliminary to such a scheme 

 directors of observatories are to be consulted. 



20. That regarding items A 6, 7, and 9 of the printed Agenda, namely, mean annual 

 values and secular change, diurnal inequalities, and publications, the Executive Com- 

 mittee is to consider and formulate any recommendations they maj^ think desirable. 



(Signed) C. Chree, President. 

 (Signed) Louis A. Bauer, Secretary. 



Researches of the Department of Terrestrial Magnetism (Vol. IV); Land magnetic observa- 

 tions, 1914-1920, by L. A. Bauer, J. A. Fleming, H. W. Fisk, and W. J. 

 iPeters, and special reports by J. A. Fleming, H. W. Fisk, and S. J. Barnett. 

 Carnegie Inst. Wash. Pub. No. 175 (Vol. IV), 475 pages, 9 plates, and 17 

 text-figures (1921). 



This volume contains, in continuation of the previous vokimes of "Re- 

 searches" (No. 175, Vols. I, II, and III), and in a similar manner, the results 

 in two parts of magnetic observations made by the Department of Terrestrial 

 Magnetism as follows: (a) The results of all magnetic observations made on 

 land from January 1914 to December 1920, and (6) special reports on various 

 special researches made by members of the staff of the Department. 



The land stations for which the results are reported upon may be sum- 

 marized as follows: Africa, 447; Asia, 356; Australasia, 315; Europe, 24; 

 North America, 113; South America, 339; islands of the Atlantic Ocean, 19; 

 islands of the Indian Ocean, 30; islands of the Pacific Ocean, 104. The total 

 number of land stations is thus 1,747. The tabulation of results gives names 

 of stations, geographic positions, values of the three magnetic elements, dates 

 and local mean times of observations, references to instruments used, and the 

 initials of observers. 



Data for the determination of secular-variation have been obtained at 204 

 C. I. W. repeat localities, the reoccupations for each locality listed involving 

 from 1 to 4 stations. The great majority, 168, of these were either exact 

 reoccupations or close reoccupations (within less than 30 meters) and 36 were 

 within less than 5 km. of stations previously occupied bj"- the Department of 

 Terrestrial Magnetism. For many of these localities the repeat observations 

 were obtained not only at several stations, but also at different times during 

 1914 to 1920. In addition to these sources of secular-variation data, fully 

 150 more of the stations have been practical reoccupations (within less than 

 300 meters) or proximate reoccupations (within less than 5 km.) of stations 

 previously occupied by various exploring expeditions. 



The text preceding the tabulation of results gives a discussion of instru- 

 mental constants and corrections on adopted International Magnetic Stand- 

 ards as defined on pages 270-278 of Volume II of the Researches of the Depart- 

 ment. (For abstracts of the investigations concerned with this portion of the 

 text, see pp. 295 and 298.) A brief discussion of the accuracy of the geographic 

 positions is given, particularly as regards longitudes. The full text of article 

 on "Auxiliary tables to facilitate revisions of field magnetic observations," 

 already abstracted on pages 313-314 of the Department's report for the year 

 1919, is given, together with graphs for determining without recomputation 

 the corrections necessary in azimuth and time reductions for revised values 

 of latitude or of time. 



Somewhat extended extracts from the observers' field reports for the various 

 expeditions are given. Following the field reports there are concise descrip- 

 tions of the magnetic stations occupied during the period. 



The second section of the volume contains special reports. Abstracts of 

 these reports are given elsewhere in this report. 



