TERRESTRIAL MAGNETISM. 



No. 175. BAUER, L. A. Land Magnetic Observations, 1905-1910. (Researches of 

 the Department of Terrestrial Magnetism.) Quarto, iv-)-185 pages, 10 

 plates. Published 1912. Price $3.00. 



No. ITS. Vol. II. BAUER, L. A., and J. A. FLEMING. Land Magnetic Observations, 

 1911-1913, and Reports on Special Researches. (Researches of the De- 

 partment of Terrestrial Magnetism.) Quarto, v+278 pages, 13 plates. 

 9 figs. Published 1915. Price $5.00. 



These volumes contain the results of all magnetic observations made on land by 

 the Department of Terrestrial Magnetism from the beginning of its observational 

 work in February 1905 to the end of 1913. Descriptions of the types of instruments 

 used are given. The discussions of the general methods of the magnetic and 

 astronomical field work include, besides the general detail of selection and occupa- 

 tion of stations, specimens of field records, computations, and determinations of 

 constants and corrections. However carefully constructed, various instruments 

 give results differing by small, more or less constant, amounts, and in order to 

 secure a standard of reference, extensive intercomparisons of instruments have 

 been made at Washington, in the field, and at many magnetic observatories through- 

 out the world; with these data it has been possible to reduce the magnetic results 

 for the region covered in the publication to magnetic standards within an error in 

 general on the order of the error of observation. 



In Volume I intercomparisons of the provisional magnetic standards adopted 

 with standards of 12 observatories in the northern hemisphere and 4 in the 

 southern hemisphere, are given, as also the indirect results of observations by other 

 organizations at seven additional magnetic observatories in the northern hemisphere ; 

 these show that the provisional standards adopted are very close to international 

 standards, at least so far as all practical requirements of general magnetic survey 

 of the Earth are concerned. The corrections to these standards for the various 

 instruments used are given in detail. The results are summarized as follows: 

 Africa, 386 stations; Asia, 308 stations; Australasia, 10 stations; Europe, 36 stations; 

 North America, 328 stations; South America, 111 stations; Islands of the Atlantic 

 Ocean, 68 stations; Islands of the Pacific Ocean, 51 stations. The table of results 

 contains for each station the geographical latitude, longitude, date of observation, 

 observed values of magnetic declination, inclination, and horizontal intensity, the 

 local mean times to the nearest one-tenth hour for each element, the instruments 

 used, and the observer. The volume also contains descriptions of stations ar- 

 ranged under the same geographical divisions adopted in the table of results. 



Volume II presents the results of all magnetic observations made on land by 

 the Department from January 1911 to the end of 1913, and reports on some of 

 the special researches and equipment. It describes new magnetic instruments of 

 light and portable types, designed, constructed, and used for the field operations of 

 the Department subsequent to the work reported in the first volume, including a 

 combined magnetometer and dip circle and a combined magnetometer and earth 

 inductor. The results of the extensive intercomparisons of instruments at Wash- 

 ington and in all parts of the world are given in detail for each instrument. The 

 stations at which the magnetic observations were made between 1911-1913 may be 

 summarized as follows. Africa, 202; Asia, 83; Australasia, 284; Europe, 38; North 

 America, 48; South America, 247; Islands of the Atlantic Ocean, 16; Islands of the 

 Indian Ocean, 14; Islands of the Pacific Ocean, 16; Antarctic Regions, 30. A 

 table of results gives data corresponding to the table described for the first volume. 

 Extended extracts from the Observer's reports are given, and descriptions of 

 stations. The newly-erected research building of the Department at Washington, 

 viz., a main fireproof building containing the headquarters, laboratory, and instru- 

 ment shop; a one-story non-magnetic building to serve as a standardizing mag- 

 netic observatory; and smaller accessory structures. One section of the report 

 is devoted to the director's inspection trip in 1911 and to the observations secured 

 at Manua, Samoa, during the total solar eclipse on April 28, 1911. 



S3 



