. 
244 Influence of atmospheric Moisture on an Electric Column. 
five-cighths of an inch,in three minutes, and when the tube was 
simply touched that divergence was reduced to three-eighths of 
an inch. The column was then held to the fire for a few se- 
conds ; and on replacing it, and laying the finger on its negative 
extremity, the leaves struck the sides of the electrometer in less 
than half a minute. The finger being withdrawn, the column 
became insulated, and the strikings were. prevented: the glass 
tube was then touched in various places, as well as its waxed ex- 
tremities ; but the divergence of the leaves remained unaffected 
by it, as they also did by a continuance of the contact. 
To the above, the following observations and conclusions may 
not improperly be subjoined. 
1. That when the air is tolerably dry, simply touching the 
glass. tube is not sufficient to produce the greatest diminution 
of divergence in the leaves of the electrometer, but the contact 
must be continued for two or three seconds ; and still longer if 
the waxed extremities be touched; and when the air is very dry, 
the diminution is scarcely perceptible by.any continuance of the 
contact. 
2. When the column is in an insulated state, and the diver- 
gence of the leaves but small; whether that divergence remains 
the same, or is increased by touching the glass-tube ; if a finger 
he laid upon the negative extremity of the column, the diver- 
gence of the leaves will be quickly augmented; aud on with- 
drawing the finger, and then touching the tube, they will instantly 
be reduced to their original divergence. 
3. In a few instances when the tube has been touched in a 
considerable number of places; the leaves, after opening to their 
former extent, have ceased to diminish their divergence when 
the tube was touched; the finger having partially removed from 
its surface the film of moisture, as well as the electric fluid 
which was creeping along it; but after waiting a few seconds, 
on renewing the touching, the same effect has followed as at 
first. 
4, When the column has been, exposed to the rays of the sun, 
or to the heat of a fire ; if the moisture has been completely di- 
spersed from its surface, no decrease nor increase in the diver- 
gence of the leaves will ensue when the finger is kept in contact 
either with the glass tube or its waxed extremities. 
5. But after the moisture has been so dispersed, the electrical 
power of the column is always found to be augmented. 
6. On the whole it may be fairly concluded, that the variation 
in the electrical action of the column is principally caused by the 
greater or less quantity of moisture adhering to its surface ; ac- 
cording as the ambient air is disposed to impart moisture to 
that surface, or to take moisture from it. 
The 
