298 CARNEGIE INSTITUTION OF WASHINGTON. 



DETAILS OF INVESTIGATIONAL AND EXPERIMENTAL WORK. 



DIVISION OF RESEARCH IN TERRESTRIAL MAGNETISM. 



This division is under the immediate charge of the Director and is 

 concerned primarily with investigations relating to the phenomena and 

 causes of the Earth's magnetic field and its variations. Preparatory- 

 studies for an analysis of the terrestrial magnetic field as based upon the 

 data accumulated by the Department and cooperating institutions are 

 under way. It may be of interest to note in this connection that, for the 

 major part of the Earth, it will be possible to undertake the solution of 

 some of the principal outstanding questions with the aid of practically 

 the Department's data alone. This is a fortunate fact, because, in 

 consequence of the great war, the results of some of the national mag- 

 netic surveys made by official and other organizations will not be 

 available for a long time to come. 



Geophysical phenomena during solar eclipse of May 29, 1919. — A 

 detailed investigation has been made concerning some of the geo- 

 physical phenomena revealed during the solar eclipse of May 29, 1919, 

 and theu' possible bearing upon the physical deflection of light observed 

 during the echpse by the British expeditions to Sobral, Brazil, and the 

 Island of Principe, West Coast of Africa. We have here a problem of 

 joint interest to the geophysicist and to the astronomer. The question 

 was raised and discussed in various issues of Nature, December 1919 to 

 April 1920, by several British investigators, whether there might not 

 be appreciable abnormal refraction effects in the Earth's atmosphere 

 as caused by meteorological changes during totality, v/hich might 

 enter into the observed light deflections. The question and causes 

 of abnormal terrestrial refraction effects are of special interest also to 

 the Department in connection with the discussion of the dip-of- 

 horizon measures being made on the Carnegie. Hence a joint investi- 

 gation was undertaken by the Director and Mr. Peters, in charge of 

 the discussion of the Carnegie atmospheric-refraction observations 

 (see p. 299). The main meteorological data available are those made 

 by the Department's expeditions to Sobral and Cape Pahnas and the 

 Brazilian expedition to Sobral. The investigation can not be closed 

 until some additional data obtained by the British expeditions have 

 been supplied. (See abstracts of preliminary papers on the subject, 

 pp. 315-316.) 



Magnetic results of eclipse observations, May 29, 1919. — The mag- 

 netic observations made at about 30 stations over the globe by the 

 Department and cooperating institutions in connection with the solar 

 eclipse of May 29, 1919, were reduced and discussed. The observa- 

 tions were made at nearly all stations in accordance with the Depart- 

 ment's program of work. A first summary of results and conclusions 

 appeared in Terrestrial Magnetism and Atmospheric Electricity for 

 September 1920. A fuller account of the investigation forms a special 



