270 proceedings: philosophical society 



values of both the gradient and the ampHtude of its short-period fluctu- 

 ations. 



For the observations of the specific conductivity of the air the as- 

 piration apparatus devised by Gerdien was employed. By the use of 

 a separate apparatus for each, it was possible to make approximately 

 simultaneous observations of the positive and negative conductivities. 

 The time for a single determination was 2 minutes, and, except for the 

 time required for making frequent calibration and leak tests, the ob- 

 ser^'ations were made continuously throughout a period of 6 hours 

 symmetrical about totality. The results showed, for both signs, a very 

 marked increase in conductivity just before totality. These abnormal 

 values continued for about 20 minutes after totality when both con- 

 ductivities began to decrease. The time of return to normal afternoon 

 values, for both signs and also for the total conductivity, corresponded 

 very closely to the time when the potential-gradient regained its normal 

 values. 



A short resume of the results of atmospheric-electric observations 

 during previous eclipses by other observers was also given and com- 

 parisons made with the foregoing. 



Adjournment took place at 10:20 p.m. and was followed by a social 

 hour and refreshments. 



The 8 1 6th meeting, a joint meeting with the Washington Academy of 

 Sciences, was held at the Cosmos Club, March 15, 1919, President Hum- 

 phreys presiding. 



The address of the evening was given by Dr. H. D. Curtis on Modern 

 theories of spiral nebulae. 



This address was illustrated by lantern slides and has appeared in 

 this Journal ig: 217. 1919). 



S. J. Mauchly, Recording Secretary. 



