ELECTRIC PHA NOMENA OF THE ATMOSPHERE. 393 
duced at a very elevated temperature, it thereby acquires a ten- 
sion of several atmospheres, breaks the aqueous envelope which 
surrounds it, and escapes suddenly*. Other contacts form other 
vapours, the high tension of which occasions a series of explo- 
sions which separate the vapour instantly from the liquid by 
projecting it to a distance. It is only at this moment, it is only 
when these continued explosions take place, that the index of 
the electrometer is acted upon, and deflected in proportion to the 
temperature at which the vapour has been produced, and to the 
decrepitations which have resulted from them. Before, as well 
as after this series of explosions, whatever may be the quantity 
of vapours produced, there are never any signs of electricity, if 
foreign causes are carefully removed. 
33. This result is easily understood. Whenever there is a 
chemical action, whether a combination or segregation, an elec- 
tric phenomenon undoubtedly accompanies it. We have said 
and proved by experiments, that there is never any change in the 
molecular relations of a body without production of electricity, 
whatever may be the nature of these changes; but it is not suf- 
ficient that an electric phenomenon be produced, it is necessary 
that the unequal distribution which constitutes it be preserved, 
that the neutralization be not re-established, that, in short, there 
be an insulation, an obstacle which is opposed to the re-esta- 
blishment of the normal equilibrium. We know therefore 
that in the evaporation of solutions electricity is produced ; but 
it is not sufficient that there be separation of electricity, there 
must be preservation, and this cannot be unless at the moment 
of its production there be a perfect insulation between the two 
tensions, in order that the retrograde neutralization may not 
take place. These conditions cannot exist but when the va- 
pour is formed at a high temperature; the tension increasing 
with it, the vapour escapes with force, it projects itself to a di- 
stance, and leaves suddenly a great space, which insulates it from 
the liquid. But when the vapour forms slowly, when nothing 
separates it instantaneously from the liquid, so that it rises 
from it tranquilly, the electric recomposition takes place before 
“it has been sufficiently removed to constitute an insulating space; 
* When the liquid is turbid, or has been darkened by a solution of indizo 
the contact commences at a much higher temperature ; I have found it seve- 
ral times above 200°. The projections are then so violent that it is difficult 
to protect oneself from them, and I have seen the index of my electrometer 
blown into the air. 
WOL. III. PART XI. 2D 
