Discussion of Atmospheric-Electric Observations 



421 



The quantity R shows a faint indication of a minimum in February, but the changes 

 in R are so small that it is undesirable to discuss their origin in detail. 



Fig. 28.- 



-Variation of Atmospheric-Electric Elements during a Period of Four Months 

 on the Sub-Antarctic Voyage. 



Atmospheric-electric observations made aboard a vessel are manifestly not of a type 

 well suited to the elucidation of annual variations in the elements, since the geographic 

 location of the vessel alters continually. It is probable that ocean data on the annual 

 variation, and indeed on the diurnal variation, could be most advantageously secured 

 from observatories erected on small islands located in mid-ocean. In order that the 

 results obtained may be free from local influence, the islands should be as free as possible 

 from foliage. There are, however, very obvious practical difiiculties involved in an 

 attempt to carry on scientific work on an island whose chief characteristics are that it is 

 barren and located in mid-ocean. 



