DEPARTMENT OF TERRESTRIAL MAGNETISM. 329 



atmospheric electricity aboard the Carnegie and at the laboratory in Wash- 

 ington. The Department can now enter actively, with increased facilities, 

 upon participation in another world-wide project, namely, the mapping of the 

 Earth's electric field and the study of its variations at fixed points. For a 

 summary of the chief results of the recent work on the Carnegie, see Dr. 

 Swann's abstract, pages 337-339. 



Researches of the Department of Terrestrial Magnetism (vol. ii) : Land Magnetic Observa- 

 tions, 1911-1913, and Reports on Special Researches. L. A. Bauer and J. A. Fleming. 

 Quarto. Carnegie Institution of Washington Pub. No. 175 (vol. ii). 1915. 278 

 pages, 13 plates, and 9 text-figures. 



The first portion of this publication contains, in continuation of the previous 

 volume of researches (No. 175, vol. i), and, in a similar manner, the results of 

 all magnetic observations made on land by the Department of Terrestrial 

 Magnetism from January 1911 to the end of 1913. In the second portion are 

 given reports on some special researches. New magnetic instruments of light 

 and portable types are described, which were designed, constructed, and used 

 for the field operations subsequent to the work reported on in the first volume. 

 These new instruments include two universal-magnetometer designs, viz, a com- 

 bined magnetometer and dip circle, and a combined magnetometer and earth 

 inductor. The results of the extensive intercomparisons of instruments at 

 Washington, and in all parts of the world, are given in detail for each instrument. 



The stations at which magnetic observations were made between 1911 and 

 1913 may be summarized as follows: Africa, 207; 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. The total number of stations is thus 983. The table 

 of results (pp. 26-64) 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. From about 18 

 per cent of the results, data for the determination of the secular variation have 

 been obtained. 



Extended extracts from the observers' field reports appear on pages 65-128. 

 Following these are concise descriptions of the magnetic stations occupied 

 during the period 1911-1913 (pp. 129-182). 



The next section of the volume contains the reports on special researches. 

 The first describes in detail the newly-erected research buildings of the Depart- 

 ment at Washington, viz, a main fireproof building containing the Director's 

 headquarters, laboratory, and instrument shop; a one-story non-magnetic 

 building to serve as a testing or standardizing magnetic observatory, and 

 several smaller accessory structures for special investigations in atmospheric 

 electricity and allied subjects. The second report is devoted to L. A. Bauer's 

 inspection trip of 1911, in the course of which he visited various magnetic 

 institutions, and to the observations secured at Manua, Samoa, during the 

 total solar eclipse on April 28, 1911. On plate 10 is a full-size reproduction of 

 the photograph obtained of the eclipse, showing the coronal extensions corre- 

 sponding to a period of minimum sun-spot activity. The concluding report 

 is concerned with the results of the comparisons of magnetic standards obtained 

 by observers of the Department, during 1905 to 1914, both at magnetic 

 observatories and in the field among themselves. For a statement of the chief 

 results see pages 315-316. 



The plates contain illustrations of the research buildings of the Department 

 and of various instruments; also typical views obtained on field expeditions to 

 all parts of the Earth, and finally views of magnetic observatories. 



