118 
TKANS. OF THE ACAD. OF SCIENCE. 
interrupted descent and ascent took place from January to 
December, we find in 1862 some interruptions in the steps of 
that ladder. The electricity in February, 1862, is about four 
degrees higher than that of January, April somewhat higher 
than March, and July is the lowest instead of September in 
1861. These trifling irregularities may be accounted for by 
differences in temperature and relative humidity, and by a 
greater number of thunderstorms in 1862. January of 1862, 
for instance, was so unusually rainy, that its relative humidity 
too was unusually high, diminishing thus electricity. But 
the general features of distribution of electricity throughout 
the year are apparent in both years, and we may in that re- 
spect divide the twelve months of each year into two or three 
groups. Computing the months which give the highest elec- 
tricity and those which give the lowest in each year, we find 
that in both years the months of January, February, March, 
April, November and December exhibit the highest, and 
the months of May, June, July, August, September and Oc- 
tober the lowest electricity. The first group gives 
The aggregate monthly mean of 71.5 degrees of electricity in 1861 
and 74.6 “ « “ 1862 
While the second group gives 29.0 “ “ “ 1861 
and 25.7 “ “ “1862 
The second group, prevailed therefore in 1861, and the 1st 
in 1862. 
Or we may divide the twelve months of each year into 
three groups. The first group with the highest electricity is 
formed by the months of January, February, November and 
December; the second with a mean electricity by the moiMis f 
of March, April, May and October; and the third with ftie 
lowest electricity by the months of June, July, August agd 
September. 
The aggregate monthly mean of 
The first group in 1861 ] 
The second “ “ 
The third “ “ 
; 52.9— in 1862, 54.6 
33.5 “ 35.2 
14.1 « 10.5 
\ 
Thus in 1861 the third group prevailed, and in 1862 the 
first and second. But these differences are so well balanced 
throughout the year, that the mean of the whole year in 
1861 and in 1862 is exactly the same, namely, 8.4.\ Such an 
identity in the yearly result, even to decimals, is of course 
not to be expected every year ; but it seems to prov£, at 
least, that the yearly mean of electricity is as constant as 
that of temperature, of relative humidity, and of atmospheric 
v 
\ 
The third table, showing the daily periodicity of atmos- 
pheric electricity, confirms the daily two maxima and two 
minima of elect deify as an undeniable fact. 
0 1 2 3 4 5 6 7 8 9 10 Missouri 
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