The National tribune., 1890-03-27
GENERAL.
THE WEATHER.
Some Facts AZ 10 the Origin Of Atmospheric Elec.
trclty.
by LIEUT. j. p. FINLEY, U. s. SIGNAL SERVICE

by LIEUT. J. p. FINLEY, U. s. SIGNAL SERVICE.
fCorespondenoc invited, suggestion. doaIrcIF
aud Information checrfuy furnished Every ef
fort employed to make this Bureau of practical use
10 the readers Of The NATIONAL TRIBUNE. All
communications should be addressed Weather
THE NATIONAL TRIBUNE Oliice. Washington. d. q. !
Philosophers are by no means agreed as TO
the origin OF atmospheric electricity. Friction
Is ono Of the most common sources of electricity.
Dry air rubbing against dry air, or any other
substance, develops little If any electricity: but
moist air rubbing against the surface Of the
earth acquires positive electricity.
In violent local storms We uniformly OBJ
serve electricity OF great intensity, not as the
cause'of the disturbances but ono Of the attend
ant features. It's appearance In such cases may
be due 10 the friction OF the air upon the earth;
but we cannot consider friction 10 be the prin-
cipal source Of atmospheric electricity, because
there Is no uniform relation between the force
OF the wind aud the intensity OF the electricity
Combustion is another source OF electricity
When coal is burning the carbDnic acid gas
which escapes IL positively electrified, while
the coal has negative electricity. The atmo4-
pbere, therefore, must receive some electricity
from the combustion which takes place on the
surface Of the earth, but this cause must be en-
tirely inadequate TO account for the enormous
quantities of electricity exhibited In thunder
showers.
Another source Of electricity is found in the
processes Of vegetation. During the day plants
give out oxygen, which Is charged with mega.
tive electricity; aud during the night they
give out carbonic acid gas which is charged
with positive electricity. These two processes
| in a measure peutralize each other. The effect
Of the unequal temperature of different parts
| OF the earth is supposed 10 be a source Of at.
mospheric electricity. This cause may explain
| permanent currents existing in the earth, but
1 is not adequate TO account for the enormous
! quantity Of free electricity which often eg-
| hibits itself in thunder showers.
Since atmospheric electricity is feeble before
/ the formation OF storm and rapidly attains
| its maximum during a thunder storm IL has
| been supposed that electricity Is liberated in
| the act Of condensation Of tho vapor OF the air.
| When the steam issuing from the boiler of q
| steam-eDgine is suddenly condensed q great
amount of electricity is liberated; but il is
claimed that this electricity is not due TO sim
| pie condensation, but 10 friction of the con-
densed PARTICLES against the sides Of the orifce
| through which the steam escapes.
Evaporation is probably the principal source
Of atmospheric electricity, and IL Is found, upon
| experiment, that the evaporation of water
containing salt, or some foreign matter, will
produce more electricity than in the case of
perfectly pure water. Under such circum-
stances, then, the water of the oceans must
| IuC sOuEce Supply, hltDOuHH
fresh water must be productive TO some degree,
as the water Of the earth is never entirely pure.
IL is found that atmospheric electricity is
subject 10 diurnal and monthly changes Of in-
tensty, due In part TO actual alterations in the
amounts present, and partly 10 variations In
the c0nductivity Of the air. Just before sun
rise the electricity has a feeble intensity, be.
cause the moisture OF the preceding night has
transmitted TO the earth portion Of the cleo.
tricity which was previously present In the air.
After the sun rises new yapor ascends, and
carries with it positive electricity, so that the
actual amount Of electricity increases
In the Summer the air is warm and dry, and
opposes more resistance 10 the flow of electricity
from the higher regions of tho atmosphere.
while in Winter the moist air produces q con.
trary effect. Although the atmosphere doubt
less contains more electricity in Summer than
in Winter, IL generally produces less effect
upon an electrometer placed near tho earth's
surface. More systematic and important OBJ.
seTyatiOns of atmospheric electricity are now
being made. or contemplated than ever before
but with all the aid Of modern science it ID
admitted to be one of the most subtle inlu-
ences Of nature and the most difficult TO COM
pass
During the past three years observations
have been made at stations located about in the
same parallel between tho Mississippi River
and the Atlantic Coast 1t is believed that
better results would follow from a chain Of
stations between the Gulf of Mexico and Hud.
sons Bay.
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