14 REPORT—1849., 
the electricity of the air presents a maximum in January and a minimum towards 
the summer solstice. 2ndly. The difference between the maximum and the mini- 
mum is much more sensible in serene than in cloudy weather. In the latter case the 
numbers are 268 and 36, the ratio of which is about 7. In serene weather the 
maximum of January is 1133° and the minimum of July 35°; the ratio of these 
numbers is 36, which shows a very considerable difference. 3rdly. Throughout every 
month the electricity of the air is stronger when the sky is serene than when it is 
clouded, except towards the months of June and July, when the electricity attains 
a minimum, the value of which is nearly the same whatever be the state of the sky. 
Starting from this epoch, the electricity of the air, when the sky is clear, exceeds 
the electricity observed when the sky is entirely clouded, in proportion as the months 
advance towards January, when the ratio is more than 4 to 1. This strong elec- 
tric intensity, under a clear sky in winter, is a very remarkable circumstance, and 
had already been noticed by all the investigators of atmospheric electricity, although 
they attributed to it a much less relative value. 
Monthly variations in the Electricity of the Air. 


















1844, 1845. 1846, 1847, 
° ° ° ° 
January ...... ace 471 562 957 
February ... 5 548 256 413 
March ...... om 262 95 282 
April ass ce 93 | 94 221 
May ......... me 163 49 67 
June ......... wee 51 39 47 
July. seesares nh 58 33 43 
August ...... 90 89 57 ll 
September... 91 95 62 39 
October ....,. 110 299 98 107 
November .,. 127 334 274 160 
December ,., 340 742 799 356 
Annual mean 


Joo) Feo) Mo} As | Me} Je fh} Awol aSy | Os] Ney} BD. 
| S| ————_ | | | |) | | 


Clouded sky... | 268 |220}129] 71| 46 | 36 | 42 | 56 | 42] 75/109] 181 
Clear sky...... 1133 | 493| 261|149| 63 | 37 | 35 | 64 | 78 |168|226|571 
M. Quetelet has united in a special table the observations made during extraor- 
dinary circumstances, such as fogs, snow showers and rain, and which he did not 
employ in the calculation of the meas. From this table he has obtained the fol- 
lowing results :—The mean of the electric intensity observed during fogs is almost 
exactly the same value as that observed during snow showers; this value is very 
high, and corresponds to the mean maxima observed for the first and last months 
of the year. It does not appear that it is influenced by the seasons. The values 
observed during tranquil rain do not differ much from the ordinary values observed 
during the course of the year. In some circumstances a strong electricity, either 
positive or negative, has been observed at the approach or cessation of rain. During 
the four years included in M. Quetelet’s register, the electricity at the ordinary hour 
of observation was observed to be negative only twenty-three times ; and he remarks 
that it was only observed to be negative once during the four months of October, 
November, December and January. These negative electric indications in general 
precede or follow rain and storms; they are thus distributed: the electricity has 
been observed to be negative six times during rain, nine times before rain, five times 
after rain, twice during rain falling in distant places, once without apparent cause, 

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