ABSTRACTS 



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 this issue. 



TERRESTRIAL MAGNETISM.— Researches of the Department of Ter- 

 restrial Mognetis77i: Land 7nagnetic observations, 1905-1910. L. A. 

 Bauer, Carnegie Institution of Washington. Publication No. 

 175. Pp. vi + 185, with 10 plates. 1912. 

 This publication contains 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 

 1910. Descriptions of the types of instruments used are given. The 

 discussion of the general methods of the magnetic and astronomical 

 field work include, besides the general detail of selection and occupation 

 of stations, specimens of field records, computations, and determina- 

 tions of constants and corrections. Ho'^ever carefully constructed, 

 various instruments give results differing by small more or less constant 

 amounts and hence arises the necessity of adopting some standard of 

 reference. The Department has made for this purpose extensive inter- 

 comparisons of instruments at Washington, in the field, and at many 

 magnetic observatories thruout the world; with the data thus obtained 

 it has been possible to reduce the magnetic results for the region covered 

 in the publication to magnetic standards within an error in general in 

 the order of the error of observation. The intercomparisons of the pro- 

 visional magnetic standards adopted with the standards of twelve 

 observatories in the northern hemisphere and four in the southern hemi- 

 sphere 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 require- 

 ments of a general magnetic survey of the earth are concerned. The 



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