WISLIZENUS — ATMOSPHERIC ELECTRICITY. 



293 



sively during the day first a maximum and then a minimum 

 in electricity, and how the decreasing power of the sun's rays 

 should every evening and night cause at first a maximum 

 and then a minimum in electricity. It seems to me, that 

 there must exist some other cause for this daily periodicity. 

 I suppose, that the daily periodicity of positive atmos- 

 pheric electricity is the result of the daily contest going on 

 between the sun's rays and the humidity of the atmosphere. 

 At a certain daily period of this contest, when, as it were, an 

 equilibrium is reached between the two contending powers, 

 a maximum of electricity takes place ; and, when either the 

 one or the other power preponderates, a minimum ensues. 



From table 3 and diagram 4 we perceive that temperature 

 and relative humidity represent a daily curve with inverse 

 direction. While temperature gradually rises from morning 

 till 3 o'clock in the afternoon and falls in the night until 

 morning, relative humidity falls gradually from morning till 

 3 o'clock in the afternoon and then rises through the night 

 until morning. Now the point of equilibrium between tem- 

 perature and humidity is reached, according^ to my observa- 

 tions, about 9 in the morning and about 6 in the evening, 

 and a decided preponderance of temperature takes place at 3 

 P.M. and of humidity at 9 P.M. Hence the two maxima 

 and two minima of electricity at those hours. A comparison 

 between the yearly mean of temperature and humidity and 

 the yearly mean of electricity at the hours of maxima and 

 minima will make this still plainer. 



The yearly mean of temperature is 56 . 2 



" " at 9 A.M. . . 54.4 



« " " at 6 P.M. .. 58.1 



« " " at 3 P.M. .. 62.3 



" " " at 9 P.M. .. 53.3 



The yearly mean of relative humidity is 69.2 



« " " at 9 A.M. 70.6 



" " " at 6 P.M. 65.8 



" " " at 3 P.M. 56.9 



" " " at 9 P.M. 77.0 



TEMPERATURE. 

 9 A.M. I 54.4 



6 P.M. 58.1 



RELATIVE HUMIDITY. 



56.9 3 P.M. 



77.0 9 P.M. 



It becomes thus apparent that temperature and humidity 

 approach both at 9 A. M. and at 6 P. M. their yearly mean 

 and come to a state of equilibrium, producing the maxima of 

 electricity ; while at 3 P.M. and 9 P. M. the divergence from 

 the yearly mean becomes greater, producing the minima. 

 The approach would probably be still nearer and the diverg- 

 ence greater if I could make my observations every hour in 

 the daytime, and could continue them through the night till 



