The Wichita daily eagle. [volume] (Wichita, Kan.) 1890-1906, 1894-07-21
DUsT'S PART IN NATURE.

DUST'S PAaT IN NATURE.
Fro~' the Literary Digest
When ray of sunlight falls through
an.aperture into darkened room it is
rendered visible as far as it extends.
What we actually see, however, is not
the ray of light, but the particles of
floating dust rendered visible by it. 1t
might appear, at first glance, that the
part played by dust particles in nature
is of no great scientific or general in
terest; as a matter of fact, however,
they play very important role. Dust
Is an important factor in almost every
phenomenon of the earth's atmosphere.
In the first place it is due to the dust
that the heavens are blue. When we lift
our eyes to the vaulted arch above US we
see sunlight reflected by every particle
of dust; there is nothing but the dust
between US and the sun to transmit its
light TO us. Light traverses all gases,
no matter what their chemical compo-
sition, in straight lines, and is irvisi
bic. The dust intercepts and reflects it
on all sides, and makes the whole at
mosphere luminous, in the same man.
ner as it makes the track of the suns
rays visible in a darkened room.
Without dust there would be no blue
armament; the Heaven would be black
er than we see il 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 characterize
the surface of the earth. There would
be nothing to subdue this sharp con-
trast but the moon and stars, which
would remain visible by day. The IL
Elimination of the earth would he
similar to that which we OBJ
serve when looking at the moon
through a telescope; for the
moon has no atmospheric envelope
and consequently no dust in suspen-
sion. 1t is due entirely to the dust
that we enjoy our soft, uniformly diff
fused daylight, for which our eyes are
especially adapted; and it is the dust
which contributes so much to the beau
ty of the landscape.
But. while the foregoing explains
how the dust makes the whole vault Of
heaven light. it does not explain why
il is chiefly the blue rays of the white
sunlight that are reflected, ard, only
to a small extent, the green, yellow
and red rays.
This is dependent of the size Of the
dust particles. 1t IS only the finest of
them that are borne by the air cur
rents into every stratum of air, and it
is only these fine, widely-diffused dust
particles that are of any significance
in this connection. Now let Us con-
slider the mechanism of light and the
extreme shortness Of the ether waves
which constitute its essence. These
waves, although all microscopically
small. vary conSidersb bly, in length. The
fine atmospheric dust includes many
particles large enough 20 reflect the
short blue ether waves, fewer particles
capable of rejecting green and yellow,
and still fewer large enou gh 20 infiu-
ence the long red ethereal waves. The
red light. consequently, passes through
the great majority Of TIE dust particles,
comparatively unhindered. the blue
rays, on the contrary, are intercepted
and diffused. and 50 become visible.
This IS the reason that the finest dust
and so, too, .he frnament-sppears
blue.
So, then, the finest dust appears blur.
You may observe that the wreath
that curis upward from the burning
end Of cigar Is blue, while the smoke
drawn through and exhaled j. whitish.
The particles IN the latter case have
united and become large enough 20
reject white light. so. too, n
the country on a clear day the
sky IS blue, but in the city Il appears
whitish- because Of the greater number
OF coarse dust particles in the air. II
IS especially on mountain heights that
the SKY = so intensely bluc. because
the raretied atmosphere supports only +
the finest dust particles ~ great 1
heights the SKY would he almost black /
4 there were no dust particles In sus-
pension We see Il grow pale as We .
look a. TIE lower strata q ar to-vz-i .
ire horizon
Bat why = the skv IN Italy and ia .
the tr0picS 50 much deeper blue than i
with us2 j. The dust fner there - a Z
fact. IL really 81 Not that Ener dust F.
rises there. but IN our climate the dus. .
particles are soon saturated W'ifh vva,e- .
vap0r. which makes them cuarser. In .
warmer regions however the vap0- -
talns rs vvstery character. and dos n8t i
eou6en=e OF the sozfing dust = s. ~ 4
untT The aerial currents have horne q /
10 higher and colder regions TIA; i !.
70 e.016S- .