ELECTRIC PHZXNOMENA OF THE ATMOSPHERE. 397 
tained by raising it two decimeters beneath a perfectly clear 
sky. The hygrometer was 30! losing the quantity of electricity 
necessary to reduce it from 60° to 50°, although it was sur- 
mounted by a large tuft of very fine copper wire. On moisten- 
ing this tuft, or by covering it with a wet cloth, it required only 
10’ to allow the same quantity to pass off. Another time, the 
temperature and Saussure’s hygrometer being at the same de- 
grees as in the preceding experiment, but the electrometer indi- 
cating very resinous vapours in the air, the index of the instru- 
ment, instead of proceeding towards 0°, augmented its deviation 
by several degrees. Lastly, in another experiment, made in 
the midst of a strongly vitreous fog, the index rapidly descended 
to 0°. 
39. The vapours produced at the surface of the globe, under 
a clear sky, are necessarily resinous, since they are formed at the 
surface of a body which possesses a considerable resinous fension, 
and in presence of the celestial space which does not possess it. 
These vapours preserve this tension during the whole time 
they float in the atmosphere, and are insulated from bodies less 
resinous than themselves, or from conductors to the ground. 
_ They also rise to a height above that which they would attain by 
_ their gravity, and they do not stop until the point where their 
specific lightness, added to the electric repulsion of the globe, 
is in equilibrium with gravitation. The resinous vapours are 
Maintained at a higher elevation than the neutral vapours, and 
still more than those which are in the vitreous state. The mu- 
tual repulsion which the particles of resinous vapour exert upon 
each other as insulated electric bodies, being augmented by that 
of the terrestrial globe, they are caused to recede further from 
each other; they are, in fact, more dilated than consists with 
the mere state of elastic vapour; they weigh less upon other 
bodies, and we shall see, in another memoir, that it is to these 
electric differences of the vapours that the horary and accidental 
oscillations of the barometer are owing. 
40. The first effect of such an atmospheric state is to place us 
in the centre of an homogeneous induction, resinous towards the 
earth, and also resinous towards the vapours which are above 
us; and our instruments, which only indicate differences, being 
immersed in a uniform inclosure, obey in a less degree the re- 
sinous tension of the earth, as the atmosphere contains more of 
this primitive vapour. The indication of the electroscope will 
