DEPARTMENT OF TERRESTRIAL MAGNETISM. 251 



compilations leading to the definition of the provisional "International Mag- 

 netic Standards" adopted by the Department in 1914/ and (2) detailed 

 information with tabular exhibits of pertinent data regarding the C. I. W. 

 standard instruments, particularly the maintenance of "constants" and con- 

 sistent behavior of the standard magnetometer used for horizontal intensity. 



The confirmation of the provisionally adopted standard in intensity is 

 indicated, within practical and theoretical requirements for such a standard, 

 by the results of (1) intercomparisons with observatories, where requisite 

 control of constants is maintained, for different series at widely separated 

 times, (2) negligible weighted mean differences on absolute instruments of 

 practically every tj^pe and design, constructed by makers throughout the 

 world, at field stations and at observatories, and (3) small differences on 

 apparatus using electromagnetic methods for absolute determinations of 

 intensity, including (a) the C. I. W. sine galvanometer- of the Department of 

 Terrestrial Magnetism of United States, (b) the Schuster-Smith magnetom- 

 eter' of the National Physical Laboratory of England, and (c) the Watanabe 

 electric magnetometer* of the Central Bureau of Weights and Measures of 

 Japan (see pp. 256-258). 



Tabulations summarize the results of (1) direct observatory comparisons 

 and corrections on the provisional International Magnetic Standards obtained 

 by the Department during 1905 to 1923 at 43 observatories in all parts of 

 the world, and (2) indirect observatory comparisons and corrections on 

 provisional International Magnetic Standards obtained through observa- 

 tions of other organizations at 18 observatories. 



The accumulated data show that the provisional International Magnetic 

 Standards adopted for the work of the Carnegie Institution of Washington 

 are satisfactory and well within the magnitude of unavoidable errors of 

 observation and of the determination of constants of the various types of 

 instruments used. It also appears that the precision obtainable with care- 

 fully designed magnetometers and inductors, provided instruments are care- 

 fully used and comparisons are made with reliable standards at least every 

 two or three years, is of the order 0'.2 in declination and inclination and less 

 than 1/5,000 part of the observed value in horizontal intensity. 



World magnetic survey. Louis A. Bauer and J. A. Fleming. Bull. 3, Sect. Terr. Mag. 



and Electr., Internat. Geod. Geophys. Union, 50-56 (October 1923). 

 Magnetic observatories of the Carnegie Institution of Washington. Louis A. Bauer and 



J. A. Fleming. Bull. 3, Sect. Terr. Mag. and Electr., Internat. Geod. 



Geophys. Union, 69-71 (October 1923). 

 Work in atmospheric electricity by the Department of Terrestrial Magnetism. Louis A. 



Bauer and J. A. Fleming. Bull. 3, Sect. Terr. Mag. and Electr., Internat. 



Geod. Geophys. Union, 149 (October 1923). 

 Comments on questions of the agenda. Louis A. Bauer and J. A. Fleming. Bull. 3, Sect. 



Terr. Mag. and Electr., Internat. Geod. Geophys. Union, 139-148 (October 



1923). 



The first three papers give the detailed accounts of the operations of the 

 Department of Terrestrial Magnetism pertaining to terrestrial magnetism 

 and electricity presented before the International Section of Terrestrial 

 Magnetism and Electricity at the Rome meeting in May 1922. The fourth 



1 See Res. Dep. Terr. Mag., vol. ii, 211-278 (1915); vol. iv, 395-475 (1921). 



' S. J. Barnett, A sine galvanometer for determining in absolute measure the horizontal 

 intensity of the Earth's magnetic field, Res. Dep. Terr. Mag., vol. iv, 373-394 (1921). 



' A. Schuster, On a new method for determining the Earth's horizontal magnetic forces, 

 Terr. Mag., vol. 19, 19-22 (1914). F. E. Smith, On an electro-magnetic method for the meas- 

 rement of the horizontal intensity of the Earth's magnetic field., Phil. Trans. R. Soc London, 

 A, vol. 223, 175-200 (1922). 



* N. Watanabe, An electric magnetometer for traveling, Proc. Phys. Math. Soc. Japan, 

 ser. 3, vol. 2, 210-223 (1920). 



