DEPARTMENT OF TERRESTRIAL MAGNETISM. 259 



The work at present being conducted in the subjects of terrestrial 

 magnetism and atmospheric electricity is mainly observational: 

 Either the magnetic or electric elements are determined at suitably 

 distributed points over the Earth with the view of obtaining, as 

 accurately as possible, a knowledge of the Earth's general magnetic 

 or electric condition (magnetic or electric surveys) ; or at a consider- 

 ably smaller number of points are registered the variations to which 

 the magnetic and electric elements are subject with time and with 

 varying planetary and solar conditions (observatories). There are 

 thus magnetic and electric survej^s, and magnetic and electric observa- 

 tories; but hitherto no laboratory has been established for the specific 

 purpose of assisting in the physical interpretation of the particular 

 phenomena in terrestrial and cosmical physics here concerned. The 

 recent rapid progress in the science of astrophysics is doubtless 

 attributable in no small measure to the combination of laboratory 

 with observational facilities and the enlistment of the physicist and 

 the mathematician in astrophysical problems. Just so should it be 

 and must it be with the closely related subjects, terrestrial magnetism 

 and terrestrial electricity, before similar progress may be recorded. 



The questions which are now continually arising with the advance 

 in the observational and investigational work of the Department are 

 partly experimental and partly theoretical in their nature. While 

 the special purpose of our laboratory must necessarily be to supply 

 the facilities to assist in the solution of these questions, it will often 

 arise that investigations in the general subject of magnetism and 

 electricity and allied subjects can profitably be undertaken, provided 

 the facihties be adequate. It is in fact often difficult to draw a 

 sharp dividing line between special and general interests and it is a 

 noteworthy fact that the most promising research work is being done 

 in the borderland or "twilight zone " of the older-established sciences. 

 Dr. W. F. G. Swann, formerly of the University of Sheffield, has been 

 secured as chief physicist for the proposed experimental work. 



In spite of the amount of attention which has had to be devoted 

 to the planning and supervision of the Office and Laboratory Build- 

 ing, the final reduction of the field observations has been making 

 such good progress that within a few months the manuscript for the 

 second volume of Researches of the Department, containing the 

 land magnetic observations for the two years 1911 and 1912, will be 

 read}' for the press. Good progress has also been made vnth the 

 manuscript for the volume to contain the ocean observations. The 

 tables of magnetic declination for the ocean work and chart correc- 

 tions have been published promptly, for each cruise, in the journal 

 Terrestrial Magnetism and Atmospheric Electricity. 



The compilation of past data has been continued and the effort 

 has been made to determine characteristic or suitable regions where 



