The Pascagoula democrat-star. (Pascagoula, Miss.) 1878-1920, 1894-07-06
DUST'S PART IN NATURE.

When a ray of sunlight falls through 0
an aperture into darkened room 1t fl
is rendered visible as far as 1t extends. d
What We actually see, however, is not Il
the ray Of light, but the PARTICLES OF +
floating dust rendered visible by it. I
1t might appear, at first glance, that IL
the part played by dust particles in !
nature is OF no great scientific or gem b
cral interest; as matter OF fact, c
however, they play very important i
role. Dust is an important factor In a
almost every phenomenon OF the a
earth's atmosphere. In the first place t
it is due to the dust that the heavens T
are blue. When we lift our eyes to
the vaulted arch above us we see sun
light reflected by every particle OF
dust there is nothing but the dust
between us and the sun to transmit
its light to us. Light travcrses all
gases, no matter what their chemical
composition, in straight lines, and is
invisible. The dust intercepts and re-
fleets it on all sides, and makes the
whole atmosphere luminous in the
same manner as 1t makes the track OF
the suns rays visible in a darkened |
room.
Without dust there would be no
blue tlrmament; the heaven would be
blacker than we see it on moOnlcss
nights. On this black background
the glowing sun would slime 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 contrast but the
moon and stars, which would remain
visible by day. The illumination OF
the earth would be similar to that
we observe when looking at the moon
through IA telescope; for the moon has
no atmospheric envelope, and consc-
quently no dust in suspension. 1t is
due entirely to the dust that we enjoy
our soft, uniformly diffused daylight,
for which our eyes are especially
adapted, and 1t is the dust which con-
tributes 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 mo-
explain why it is chiefly the blue rays
, of the white sunlight that is reflected
and, only to small extent, the green
red and yellow rays.
This is dependent upon the size o
the dust particles, it is only the fines
Of OF them that are borne by the air cur
rents into every stratum of air, and
les is only those fine, widely diffused dus
se- particles that are Of any signiflcanc
DIV in this connection. Now let us con
slider the mechanism OF light and tn
NJ extreme sllortncss of the ether wave
lat which constitute its essence. Thes
He waves, although all microscoplcall
mt small, vary considerably In length
The fine atmospheric dust include
an many particles large enough to rehec
old the short blue ether waves, fewer pa
lis, ticlcs capable of rejecting green an
1er yellow, and still fewer large enoug
ing to influence the long, red ether;
vas waves. Tile red light, consequent.
tell passes through the great majority
/ he these dusty PARTICLES comparative
Ind unhindered: the blue rays, on u
ght contrary, are intercepted and difluse
me and 50 become visible. This is I'll
OF reason that the finest dust-and s
He too, the flrmamcnt--appears blue.
edy So, then, the finest dust appea
old blue. You may observe that u
saw wreath that curls upward from Il
'go. burning end Of a cigar is blue, whl
to the smoke drawn through and exhaI'
1872 is whitish. The particles in the la
lrly ter case have united and become lar
enough to reflect white light. So, to
,use In the country on clear day the 81
His is blue, but in the city it is whitis
lied because Of the greater number OF du
nese PARTICLES in the air. 1t Is especial
alth on mountain heights that the sky
of. SO intensely blue, because the rarih
the atmosphere supports only the hne
year dust particles. At great heights =
1t sky would be almost black II the
nee, were no dust PARTICLES in suspenslt
We see it grow pale as we look at I
this slow strata Of air toward the hofist
'ugn But why Is the sky in Italy ana
QUO the tropics so much deeper blue tn
told with us +? Is the dust finer ther
gooo As a fact it really is. Not that fir
neoy dust rises there, but In our clint
ortl' the dust particles are soon saturat
with water vapor, which makes TIN
arlai coarscr. In warmer regions, howev
0uc" the vapor retains It's watery charac
sion. and does not condense on the floatl
plieo dust. 1t is not until the aeriaf c
|sing ron,s have horne IL to higher a
bout colder regions than is is condensed
bind. ,,,ords
's up This brings us to the most import
tne role played by dust in our attnosphe
!; ; ~ its influence In determining rainf
row due to the fact that vapor auidi
I its upon the dust particles.
;nxpM nIpso It may be accepted as beyond q
ID to tion that' OF w inc waIcr c'"po'o :
tried by the sun from the surface OF j
enty. aud sea, not one drop returns
~ !, ,To 70 has not condensed upon a particle
dust as u nucleus. This Is Gu