Evening star. [volume] (Washington, D.C.) 1854-1972, 1912-03-24
ELECTRICITY
BY LAWRENCE HODGES

very close to the earth The way this was
determined by Sir w. Thomson was to in
sulate living plant, such as grass. from the
earth, place it at these different heights, and
connect one wire of his measuring instru-
ment to it and the other wire to the earth.
His results were rather astounding at first.
At height of nine feet he found difference
of four hundred and thirty volts, or approx
mately fifty volts to the foot, at the Isle of
Arran. Other places of course showed slight
variations.
A peculiar thing about this atmospheric
electricity is that it also varies with the
time of day, being at its greatest at about
eight A. NJ, and from eight to nine P. NJ, in
summer, and ten A. NJ and six P NJ. in win
ter and lowest about three P. NJ. and mid
night. This indicates that it is highest Just
when we have the greatest change of tenn
perature and when the evaporation and fall
of dew are greatest. Some interesting points
were discovered in making these observa-
tons. An east wind always raised the posi-
tive or plus identification: while when rain
ing the potential of the atmosphere was al
ways observed to be negative or minus.
In Italy, Professor Palmieri found that
the condition was plus or positive when no
rain, hail, or snow was falling within ninety
five miles of the place of observation. Also,
if minus was found in the atmosphere, al
though there was clear sky, downfall of
some description was sure to be found near.
All the phenomena point to the earth and
atmosphere as constituting huge Leyden
jar, the earth taking the place of one of the
tinfoil plates, the higher atmosphere of the
other, while the intervening comparatively
dry air is analogous to the glass jar. Large
sparks have been obtained by sending sew
eral wires up to collect the electricity in the
air and then bringing them almost in con-
tact with wire from the earth.
1t has been noticed that powerful electric
discharges attend volcanic eruptions and
earthquakes. These are no doubt due to the
enormous amount of mechanical energy ex-
pended and to the chemical action of water
upon heated and molten rocks. Instruments
called microphones, if buried in the earth, give
warning of these eruptions before they occur.
One historical incident brought this dis
covery about. During one of the great
eruptions, that of Mount Krakatua in 1888,
the telephones in Singapore, which is over
five hundred miles away were rendered use
less for talking, great roar similar to that
of a waterfall being heard occasionally pune
tured with sharp pistol like reports. This
effect was traced as having its origin in
short length of cable submerged and affected
by the trenOrS of the earth.
1t is thought now that cyclones and water
spouts are also electrical in character. Pro
fessor Douglas, of Michigan, has produced an
imitation cyclone in his laboratory by sus-
pending a large circular disk of copper to
silk threads and then charging the copper
with electricity. The result is rather start
ling. AS the plate is carried over the table
it whirls rapidly (while the threads take on
the well known funnel shape) and picks up
all loose objects in its path.