ELECTRIC PHA NOMENA OF THE ATMOSPHERE. 391 
length ; the longer this stem is, the less will be the portion which 
will return to the gold leaves, and the less will they diverge ; it 
_ is therefore in vain to take poles to study this phenomenon, the 
maximum of which manifests itself with a rod of three or four 
decimeters in length, terminated by a ball seven or eight cen- 
timeters in diameter. By employing masts, balloons or kites, it 
is not the electricity of induction in the electrometer, but its ra- 
diation which is augmented, and consequently the electricity 
repelled alone remains in the conductor, and becomes perma- 
nent if it be insulated, or gives a continuous current by its 
passing off to the ground if it be not. The employment of poles 
has led to another error which ought to be noticed. When the 
extremity of a wire is held to the end of a pole, and it is inclined 
without being raised, two contrary manifestations may happen : 
if it be elevated above all surrounding terrestrial bodies, the ex- 
tremity of the pole is lowered by inclining it, and the electro- 
Scope then gives a resinous sign. If, on the contrary, a portion 
of the building be near, from which the end of the wire recedes 
on inclining the pole, it is really receding from the ground, and 
then the sign is vitreous. 
Cuaprer II. 
Of Vapours produced at a High Temperature. 
4 30. The preceding experiments have been made leaving out 
of consideration bodies the presence of which might complicate 
the result ; we have supposed them to take place under a per- 
fectly serene sky and in the midst of an atmosphere which con- 
tains but little aqueous vapour. We must now mention what 
are the changes which arise when the atmosphere becomes 
charged with vapour. 
31. One fact respecting the electric state of the atmosphere 
has been proyed to be nearly general, viz. that its induction di- 
minishes when the quantity of elastic vapour augments ; the elec- 
trometer} must be raised much higher in order to obtain a di- 
vergence equal to that of an experiment made under a serene and 
dry sky. According to the humidity of the air, it must be raised 
one, two, or ten meters, to obtain a sign of electricity, which is 
easily obtained by raising it two decimeters under a clear sky. 
This difference in the electric manifestations is not peculiar to 
the moveable instruments. The fixed apparatus are also affected 
