14G 
PROPAGATION OF AERIAL ACTI05. 
the season of drought, from December to March, had been 
constantly, in the day-time, from T7 to 2 lines, becomes 
extremely variable from the month of March. It appears 
nil during whole days ; and then for some hours the pith- 
balls diverge three or four lines. The atmosphere, which 
is generally, in the torrid as well as in the temperate 
zone, in a state of positive electricity, passes alternately, 
for eight or ten minutes, to the negative state. The season 
of rains is that of storms; and yet a great number of 
experiments made dtu-ing three years, prove to me that it 
is precisely in this season of storms we find the smallest 
degree of electrio tension in the lower regions of the atmo- 
sphere. Are storms the effect of this unequal charge of 
the different superincumbent strata of air? What pre- 
vents the electricity from descending towards the earth, in 
air which becomes more humid after tho month of March ? 
The electricity at this period, instead of being diffused 
throughout the whole atmosphere, appears accumulated on 
the exterior envelope, at the surface of the clouds. Accor- 
ding to M. G-ay-Lussac it is the formation of the cloud itself 
that carries the fluid toward its surface. The storm rises in 
the plains two hours after the sun has passed the meridian ; 
consequently a short time after the moment of the maxi- 
mum of diurnal heat within the tropics. It is extremely rare 
in the islands to hear thunder during the night, or in the 
morning. Storms at night are peculiar to certain valleys ol 
rivers, having a pecul'ar climate. 
What then are the causes of this rupture of the equili- 
brium in the electric tension of the air? of this continual 
condensation of the vapours into water? of this interruption 
of the breezes ? of this commencement and duration of the 
rainy seasons? I doubt whether electricity have any in- 
fluence on the formation of vapours. It is rather the for- 
mation of these vapours that augments and modifies the 
electrical tension. North and south of the equator, storms 
or great explosions take place at the same time in the 
temperate and in the equinoctial zone. Is there an action 
propagated through the great aerial ocean from the tem- 
perate^ zone towards the tropics 1 How can it be con- 
ceived, that in that zone where the sun rises constantly 
to so great a height above t he horizon, its passage through 
