292 TRANS. OF THE ACAD. OF SCIENCE. 



electricity. The average mean of the numerical prevalence 

 of winds was during these four years — 



In the six warmer months, from April to September, 

 E. W. N. S.W. N.E. S. N.W. S.E. 



58, 100, 111, 133, 140, 143, 145, 259; 



And in the six colder months, from October to March, 

 E. N. N.E. S. S.W. N.W. W. S.E. 



57, 72, 80, 125, 141, 172, 199, 247. 



The principal difference between these two seasons is, that 

 in the six warmer months the N.E. and N. winds were a lit- 

 tle more prevalent, and in the six colder ones the W. wind ; 

 while in both of them the S.E. wind surpassed all the others 

 in frequency, being our prevalent wind throughout the year. 

 By summing up the N., N.E. and N.W. winds in one col- 

 umn, the S., S.E. and S.W. winds in another, and calling 

 them northern and southern winds, we find that the northern 

 and southern winds prevailed in the warmer and in the 

 colder portion of the year in the following proportion : 



IN THE SIX WARMER MONTHS OF THE TEAR, 



395 northern and 535 southern winds. 



IN THE SIX COLDER MONTHS OF THE YEAR, 



324 northern and 513 southern winds. 



This does not agree very well with the opinion of those phys- 

 icists who ascribe the origin of positive or negative electri- 

 city to the prevalence of polar or equatorial currents of air. 



Besides the monthly periodicity of positive atmospheric 

 electricity, there exists yet a daily one, which is illustrated 

 by diagram 4 and table 3. We see there, that two max- 

 ima and two minima of electricity appear in the twenty-four 

 hours; the first and greater maximum about 9 A.M., the sec- 

 ond lesser maximum about G P.M.; and the first and greater 

 minimum about 3 P.M., the second lesser one about 9 P.M. 

 Prof. Dellmann ascribes this daily periodicity to the direct 

 action of the sun's rays, assuming that the first electric max- 

 imum appears soon after a minimum of heat in the morning, 

 and the first electrical minimum soon after a maximum of 

 heat in the evening. But this supposition does not corre- 

 spond with the result of my observations made in St Louis. 

 The first electrical maximum here appears about three hours 

 after sunrise, and the first electrical minimum does not fol- 

 low but coincides with the greatest heat of the day, about 3 

 o'clock in the afternoon; the second electrical maximum ap- 

 pears about sunset or soon after, and the second minimum 

 about 9 o'clock in the evening and is prolonged till about 3 

 o'clock in the morning. I am unable to understand, how 

 the increasing power of the sun's rays should produce succes- 



