DEPARTMENT OF TERRESTRIAL MAGNETISM. 279 



The Department, through its ocean work, is at present conducting 

 the chief researches pertaining to the geographical distribution of the 

 atmospheric-electric elements. 



OCEAN MISCELLANEOUS WORK. 



Besides the observations in terrestrial magnetism and atmospheric 

 electricity, the following additional work has been carried out aboard 

 the Carnegie, as far as the conditions and hmited personnel permitted : 



(a) Atmospheric-refraction observations by measuring the dip of the 

 horizon with the \aew of collecting the necessary data for the 

 gradual improvement of the refraction tables used by mariners 

 in determining geographic positions of ship. Aside from the 

 practical importance for safe navigation to have regions and 

 causes of more or less abnormal atmospheric refraction indi- 

 cated, such data are also of scientific interest for the perfection 

 of the theory of atmospheric refraction. Nearly 4,000 observa- 

 tions in all parts of the ocean have been made aljoard the Galilee 

 and the Carnegie from 1907 to 1920. (Concerning studies and 

 results of the accumulated data, see pp. 299 and 300.) 



(b) Meteorological observations in cooperation with the United 



States Weather Bureau and in connection with the observa- 

 tions in atmospheric electricity are made daily, A large amount 

 of meteorological data has been suppHed to the Weather Bureau 

 during the period 1905-1920. Special attention has also been 

 paid to occurrences of thunder at sea and to its distances from 

 land. Any other phenomena of interest, such as storms, polar 

 lights, St. Elmo's fire, etc., are diligentl^^ recorded. Further- 

 more, photographs of clouds are being made in accordance with 

 the suggestions of Professor W. J. Humphreys, of the United 

 States Weather Bureau. 



(c) Geographic data of importance pertaining to charted positions of 



islands or of coasts are obtained from time to time. Notable 

 contributions of interest to the geographer and to the mariner 

 have already been made, particularly on some of the special 

 cruises, such as that of the circumnavigation of the Subantarc- 

 tic regions by the Carnegie December 1915 to April 1916. 



(d) Ocean-current observations have been made in the past as Vv'as 

 found possible. During the present cruise (VI), special studies 

 are being made in cooperation with the Department of Marine 

 Biology with apparatus and according to directions furnished 

 by Dr. Mayor. 



(e) Rock specimens are being collected at ports of call in cooperation 



with the Geophysical Laboratory for Dr. Washington's investi- 

 gations. 



LAND MAGNETIC-SURVEY WORK AND SPECIAL EXPEDITIONS. 



As has already been intimated, it has been necessary, because of the 

 increased cost of field-work and lack of available personnel, to limit 

 the land magnetic surveys even for areas over which data are urgently 

 required for the completion of the magnetic charts of the globe. In 



