WISLIZENUS — ATMOSPHERIC ELECTRICITY. 11 



even a whole day ; changing with their appearance the posi- 

 tive electricity of the atmosphere into intensely negative, 

 and leaving at their disappearance the atmospheric electri- 

 city at zero or feebly positive, in the same manner as thunder 

 storms do. What is the particular action of these dry 

 storms in regard to electricity '? Is mechanical friction a 

 prime agent in them ? or, considering their southern origin, 

 thermo-electricity ? 



I refer in my journal to the following dry storms : 



22d February, with S. wind. 



3d. The quantity or intensity of the positive atmospheric 

 electricity is very unequal throughout the year; highest in 

 winter and lowest in summer. The diagram, No. 1, is in- 

 tended for illustrating this law of its distribution among the 

 different months. It is shown, there, that the positive electri- 

 city is most intense in January, falls then gradually every 

 month to its lowest figure in September; then rises again sud- 

 denly in October, November, and December, to a point some- 

 what lower than in January. It forms, therefore, from Jan- 

 uary to December, a regularly descending and ascending scale. 

 In the months of June, July, August, and September, in which 

 electricity is the lowest, the descent is more moderate than 

 in the rest of the year. I will mention, in this connection, 

 that these four months constitute our hottest as well as our 

 sickliest season of the year. 



4th. The regular distribution of positive electricity through 

 the different months does not correspond to the monthly 

 relative humidity, but corresponds more, though not quite 

 exactly, in inverse ratio to the monthly mean of temperature. 

 This is illustrated by diagram No. 2. 



5th. There is a regular daily periodicity in the develop- 

 ment of positive atmospheric electricity, manifesting itself by 

 two maxima and two minima in the twenty-four hours ; the 

 first, or greater maximum, taking place about nine in the 

 morning; the second, lesser, about six in the evening; and 

 the first minimum occurring about three in the afternoon, 

 the second about nine in the evening, or probably between 

 midnight and morning. For want of sufficient observations 

 during the night, I cannot fix the hour of the second mini- 

 mum with such precision as the others. 



To ascertain this periodicity, I made sometimes in the 

 winter, when the sky was clear and the weather fair and con- 



