ELECTRICITY OP THE AIR. 
433 
the lower stratum of air, and equilibrates the negative 
electricity of the earth. The positive and negative elec¬ 
tricities of the upper regions of the atmosphere are kept 
apart by the extreme dryness which must prevail there. In 
the lower stratum absolute dryness does not exist. It is 
more or less moist, constantly disturbed, and traversed, 
although wdth considerable difficulty, by the positive elec¬ 
tricity, which can at times unite with the opposite electricity 
of the earth; but these never exist in intimate connection. 
The action is like that of two conductors charged with oppo¬ 
site electricities and placed at a distance: the opposite 
fluids tends to unite through the more or less moist air that 
is interposed, but their charges remain the same. If the 
losses are constantly renewed, the positive fluid of the upper 
layer gives rise to all the electrical phenomena that w^e ob¬ 
serve upon our globe. Being partially retained by the dry¬ 
ness and relative immobility of the stratum in which it finds 
itself, it operates through the lower stratum, which is always 
agitated and always more or less humid, and partially para¬ 
lyses the electricity indicated by our instruments on the 
surface of the globe.^^ 
In our northern hemisphere, the electricity is stronger in 
winter than in summer. The layer of the atmosphere that 
is constantly disturbed is not so thick at this season, and 
thus we are closer to the upper layer. In the course of a 
year, this augmentation of electricity and diminution of 
height becomes very apparent; between June and January, 
or December, the variation is as much as 1 to 10. Nor 
is the diurnal variation less noticeable; the electricity be¬ 
comes stronger towards the approach of night, and its 
minimum occurs a little after the hours of strongest heat 
during the day. It is towards three o^clock p.m. in the 
summer time that the electrified layer w’hich acts upon 
our instruments appears to be furthest removed from the 
earth.^^ It should also be remembered that as heat aug¬ 
ments, and the air becomes drier, its conducting power is 
diminished. During the night the solar action is insen¬ 
sible, and the variation is much less, and that which 
occurs appears to be the result of changes in the opposite 
hemisphere. 
tliesis, and our exi)lanatioii would be simplified. There would, iu fact, re¬ 
main only the positive electricity below the superior envelope of our atmo¬ 
sphere, which would paralyse on one side the negative electricity of the sun, 
and on the other would act through the inferior envelope and paralyse the 
negative electricity on the surface of the globe. We must then admit that 
the electricity of the sun and the earth are of the same kind. 
