16 BAUER— ATMOSPHERIC ELECTRICITY. [April 24, 



Sailing again from Hammerfest on July 25 she entered the harbor 

 of Reykjavik, Iceland, on August 24, having reached the latitude of 

 79° 52' North, off the northwest coast of Spitzbergen. Leaving 

 Reykjavik on September 15, the Carnegie arrived at Greenport, 

 Long Island, on October 12, returning to Brooklyn on October 21, 

 1914. 



The observations in 1914, comprised, in addition to the magnetic 

 and meterological data, measurements of the potential-gradient, the 

 conductivities for the positive and negative ions, and the radioactive 

 content. Measurements of the ionic numbers were also made during 

 the passage from Greenport, through Long Island Sound to New 

 York. The whole of the observations, with the exception of a few 

 measurements in Long Island Sound by Dr. Swann, were taken by 

 Observer H. F. Johnston. 



The average values of the potential-gradient, atmospheric con- 

 ductivity, and radioactive content for the whole cruise were, re- 

 spectively, 93 volts per meter, 2.52 X lO"* E. S. U., and 23, the last 

 number being expressed in Elster and Geitel units. The average 

 value of the earth-air current for the whole cruise was y.y X lO"^ 

 E. S. U. per sq. cm. 



The atmospheric-electric elements were measured daily between 

 the hours of 9 A. M. and 12 noon. The observations as far as they 

 go indicate a general increase of the potential-gradient from sum- 

 mer to winter, which is in accord with land observations for the 

 daily mean values. The conductivity also shows a general increase 

 from the beginning of the cruise (June 8, 1914) to about the end of 

 September, when a maximum occurs, after which the conductivity 

 falls. 



No marked variation of the atmospheric-electric elements with 

 temperature or humidity was found. However, an indication is 

 shown of a variation of the conductivity with latitude; a maximum 

 for the latitudes involved occurring in the neighborhood of 50° 

 North. These conclusions with regard to the variation of the ele- 

 ments with season, latitude, etc., must be looked upon as tentative 

 owing to the small number of data involved. 



The conductivity appears to have an especially low value in the 

 neighborhood of the American coast. In Long Island Sound, 



