362 Reports on Special Researches 



problems successfully and harmoniously. No commander of vessel and no one 

 set of observers can be kept continuously engaged on the strenuous program which 

 even but three or four great problems entail. New men must be continually 

 trained to assume the responsibiUties and tasks of their predecessors. 



The preceding paragraphs must suffice to show why it is necessary to Umit our 

 ocean investigational work to subjects which fall naturally within the province of 

 the work of the Department of Terrestrial Magnetism of the Carnegie Institution 

 of Washington, and why also we are prohibited, for the present at least, from 

 undertaking some other important lines of inquiry. 



It is hoped that these prefatory remarks will serve to introduce the reports on 

 special ocean researches, contained in this volume and subsequent ones, as also 

 to give a shght indication of the difficulties of administration and direction. 



The problem which naturally suggests itself as closely related to that of 

 terrestrial magnetism is that of terrestrial electricity. By the latter term is meant 

 the science pertaining to the electrical phenomena exhibited by the Earth and the 

 atmosphere. The subjects of investigation embrace: (a) the electric currents 

 circulating within the Earth's crust, (6) the Earth's electric charge, and (c) the 

 conducting properties of the atmosphere. Subject (a) at present is one of combmed 

 laboratory and observatory investigation. Subjects (6) and (c) together form the 

 science termed "atmospheric electricity." It is only with regard to field observa- 

 tions and results in the latter that the present report concerns itself. 



Professors J. Elster and H. Geitel, in their letter to the Carnegie Institution of 

 Washington, dated Wolfenbiittel, Germany, January 26, 1902, made the following 

 recommendations : 



With the earnest hope that this proposal may meet with your approval, we beg leave 

 to suggest that it would be in full harmony with the proposed plan to combine with the 

 organization of international magnetic work also the inauguration of observations pertaining 

 to the electric condition of the Earth and of the atmosphere, even though this at present 

 may be possible only to a limited extent. 



As the principal electric problems, we might name the determination of the strength 

 of the Earth's electric field and of the electric conductivity of the atmosphere (the so-called 

 dissipation of electricity), and the investigation of earth-currents and the aurora. 



Since these matters have been investigated only within comparatively recent times, the 

 methods of observation and of reduction and the theoretical utilization of the results are as 

 yet very imperfect. Nevertheless, there is reason to hope that, even with the present 

 means, relationships between the electric phenomena of the atmosphere and the Earth's 

 magnetic phenomena can be disclosed. 



At comparatively small cost for instrumental means and without adding very much 

 to the work of the observer, it would be possible, in our opinion, to institute systematic 

 measurements of the electric intensity of the Earth's field and of the conductivity of the 

 atmosphere at a few magnetic observatories as widely distributed as possible. A few years' 

 results at these places would then show whether it would be desirable to increase the 

 number of stations or expand the work in other directions. 



Since their proposals were made, these eminent pioneer investigators in 

 atmospheric electricity have unceasingly shown their interest and have rendered 



