The Anderson intelligencer. [volume] (Anderson Court House, S.C.) 1860-1914, 1894-07-18
Dust In Nature.

Without dust there would be no
blue armament; the heaven would be
blacker than we sec it on moonless
nights. On this black. background
the glowing sun would shine out
sharply, and the same sharp contrast
Of Intense light and deep shadow
would characterizc the surface of the
earth. There would be nothing to
subduce this sharp contrast but the
moon and stars, which would remain
visible by day. The illumination OF
the earth would be similar to that
which We observe when looking at the
moon through d telescope; for the
ihoJn has no atmospheric envelope,
and, consequently, no dust in s1s-
| pension. It is due entirely to the
dust that we enjoy our sofs, uniform
ly difused daylight, for, which our
eyes are specially adapted and it is
the dust which contributes so much
to the beauty of the landscape. But
while the foregoing explains how the
dust makes the whole vault Of heaven
light, it does not explain why it is
chiefly the blue rays Of the white sun
light that are reflected, and only to
| small extent the green, yellow and
red ray. This is dependent upon the
size of the dust PARTICLES. It is only
the finest of them that are borne by
the air currents into every stratum OF
air, and it is only these fine, widely
difused dust particles that are OF any
significance in this connection. Now,
let US consider the mechanism Of light
and the extreme shortness of the eth
er waves which constitute its essence.
These waves, although all microscopi-
cally small, vary considerably in
length. The fine atmospheric dust
includes many particles large enough
to reflect the short blue ether waves,
fewer particles capable Of rejecting
green and yellow, and still fewer large
enough to influence the long red eth
eral waves. The red light, conse-
quently, passes through the great
majority Of the dust PARTICLES COM
pa, atively unhindered; the blue rays
on the contrary, are intercepted and
diffused, and so become visible. This
is the reason that the finest dust.and
so, too, the armament appears blue.
So, then, the finest dust appears
blue. You may observe that the
wreath that curls upward from the
burning end of cigar is blue, while
the smoke drawn through and exhaled
is whitish. The particles in the lat
ter case have united and become large
enough to reflect white light. So,
too, in the country, on clear day,
the sky is blue but in the city it ap-
pears whitish, because Of the greater
| number of coarse dust particles in the
air. 1t is especially on mountain
heights that the sky is so intensely
blue, because the rarefcd atmosphere
supports only the finest dust parti-
cles. At great height the sky would
be almost black, if there were no dust
particles in suspension. We see it
grow pale as we turn our eyes to the
lower strata of air toward the horizon.
But why is the sky in Italy and in
the tropics so much deeper blue than
with us Is the dust finer there ?
As q fact, it really is. Not that finer
dust rises there but in our climate
the dust particles are soon saturated
with water vapor, which makes them
coarser. In warmer regions, however,
the vapor retains its waeery character
and does not condense on the floating
dust. It is not until the aerial
currents have borne it to higher and
colder regions than it is condensed to
clouds.
This brings us to the most impor-
tant role played by dust in our atmos-
phere: it's influence in determining
rainfall, due to the fact that vapor
huidiAes upon the dust PARTICLES. 1t
may be accepted as beyond question
that of all the water eyaporated by
the sun from the surface Of land and
sea, not one drop returns which has
not condensed upon a particle ct dust
as nucleus. This is easily Demon
strated. We fill large flask with air
which has been filtered through cotton
waddings until all original dust is
driven out and the flask is full OF
dustless air. Into this dustless air
turn a current Of steam from kettle
and you will find it transparent, and,
therefore, invisible. Not trace of
the cloudy appearance we associate
Nth oteam The only thing noticea
BILE is that the inner walls of the flask
begin to drip the vapor condenses
here as it cools, because there is moth
ing else for it to condense on. But
blow ordinary dust-laden air into the
flask and the vapor at once assumes
the familiar cloudy appearance due to
it's condensation on the dust PARTICLES,
and it begins to rain in the flask. The
reason for this is that the vapor con,
denses on the dust particles and
freights them until they sink as rain
drops. 49,,
Without dust, then, we would have
no fog, no clouds, no rain, no Brilliant
hued sunsets, no cerulean sky. The
surface of the earth itself, the trees,
the houses, along with man and beast,
would be the only objects on which
the vapor could condanse, and these
would begin to drip whenever the air
was cooled sufficiently. In winter ev-
erything would be covered with ice:
Our clothes would become saturated
with water condensing upon them.
Umbrellas would be of no avail. The
vapor-laden atmosphere, moreover,
would penetrate to our rooms and con-
dense upon the walls and furniture.
In short, the world we live in would
be quite another world if there were
no dust. Since scientists began to
realize the important part played by
dust in the economy Of nature, meas
ures have been taken to count the par
ticles in given space. In London
and in Paris at the surface cubic
centimeter has been found to contain
nearly quarter of a million PARTICLES.
On the top of the EiHel Tower there
are about half as many, while in the
high Alps there are only about two
hundred particles to the centimeter.
A great deal of the dust at high alti-
tudes is cosmic dust, consisting like
the meteorites of carbon and lron.-