New-York tribune., 1901-10-20
MECHANISM OF A SUNSET.
COLOR EFFECTS OF MICROSCOPIC DUST
PARTICLES.
Arthur II. Bell, in knowledge.

Arthur H. Bell in knowledge.
Most people if they were asked to state the
color of the would say that it orange, |
and they would confidently assert that the
color of the atmosphere was blue. Recent re
searches and Investigations however. point to
the conclusion that the real color of the sun Is
blue. while that of the atmosphere surrounding
the earth is orange. Commonly the earths at
mosphere appears so transparent and trans
lucent that it is hard to realize the fact that
it has as much effect on the light and heat
coming from the sun as If IT were a roof OF
thick glass. But the atmosphere is very far
from being colorless as it seems to be, and
the best way of discovering its true tint is. not
to gaze Immediately overhead, but to look away
toward the horizon. BY so doing the at
mosphere will be seen as it were, in bulk; for
overhead there is only small accumulation
of il compared with the many miles OF thickness
through which the vision travels when the eye
looks toward the horizon
The atmosphere surrounding the earth theh
may be likened to a screen Of an oranE" color
| and it will readily be understood that any hsht
passing through this screen viii experience
some remarkable notifications. Now as al
ready stated. il appears highly prohab" thtt
sllpposing any could the sun from "A
position outside the earths atmosphere the
light coming from this Centra. luinlnary wou'u
he seen 10 be. not Whit, but blue. This blu" is
Of course. not pure m"noChromdtc blue. anu
the expression really means that 1t sums up the
dominant note in the color scheme. w nat
therefore thu atmosphere may he considered |"
do is 10 stop out or absorb, all the coIoTs al
thu. blue end Of the speo trufn, the residue inter
ing through to the earth as white hight Whch
tn. RAYS Of light first left the sum- the blue rays
Mrrc the strongest: but very soon after thtS
entered the carth's atmosph"r" their progress
was impeded. and of all tn" rays Jourf'!IhE
from the sun they quickly be, anne the weakest
ON the other hand. the red rays winch at hrst
were inconspicuous had the facility of penc-
tratins the earthS atmosphere, ana Were the
most in evidence at the end of their long Jour
nry. .,.-
investigating "A sunset Is To realize that the
"a hite light from the sun which is commonly
supposed to be composed OF the seven primary
coors should rather be thought of as a residue
/ Of the original Tadiaticns iurther important
point is bear in mind that all radlatlohs ol
/ light of different wave lenSthS. ms l'V.
indeed is at the very foundation. So To speak
of all sunsets and il is the prime agency pS
which their flaming, gorgeous UNITS ana '"lolS
are produced IT is due to this fact. for IN
stance that in the ncighborhOod OF large towns
/ the snn nearly always appears to set IA red
hall of fire The rays of light at the red end OF
/ the spectrum are of a much longer wave length
/ than any of their fellow rays. and so are the
best qualified for penetrating the dense banh Oh
haze which commonly floats over all large
towns and cities. In such localities, as the sun
sinks to rest, the green rays are first aDSorpeu
| by this bank of haze. ana then the yelio"' ailu
| lastly the orange and the red, the latter. more
often than not being the only ones to get
through at all careful observation OF sun
set will reveal the fact that the colors fade IN
| the above mentioned order, and the reason they
do is that they are of different wave
lengths
At many of the observatores scattered
throughout the world. not only are sunsets thus
reIegated to certain definite classes, but in or
der to give the record a scientific value still
| further particulars concerning the sunset are
/
CARDS their position in the sky. or as regards
altitude and azmuth, as the terms are, are OBJ
served; while the time at which the colorS were
| seen and any increase or decrease i'll the brill
/ lance of the coloring would also De considered
/ worthy of place in the records In all Such
! systematic observa tions the time when the col
| Ors were at their brightest and when they faded
away would be noted, and further. in order to
! make the record quite complete, the time of sun
set or sunrise would also be registered.
! Now the color in the sky may, as it We're. be
painted ON the clouds or on the hazy air or on
the omen sky itself AS regards the latter the color
/ that is most conspicuous Is, of course, the blue
and in seeking for the origin OF TINS TINT IL VIII
bc found that the search leads to an explanation
II MANY of the other colorS. On looking up into
the ky on clOudless, sunny day, when the
/ swallows. perhaps, flying high that they
appear but as tiny speckS in the dome of blue,
! il seems almost Impossible to think OF the at
! mospherr AZ being otherwise than perfectly
clear and translucent. 1t is, however. in real
ity charged with minute dusty particles, which
have always been found in rlyriads, whenever
/ he atmosphere has been tested either over the
open sea or at the top of high mountains. There
/ is an ingenious instrument. indeed, by which the
. number of these atoms of dust i'll any given
ulantitv of air may be counted, and by its aid
: SAMPLES of air in many different parts of the
world and at different seasons Of the year have
/ been analyzed, and the atoms counted. The
sources flom which this atmospheric dust is
! obtained are large. From the land. and more
especially from deserts, dust is continually ris-
| ing and the dust so raised IS carried by the
winds to all parts. SpiculeS of salt too, leap
from the sea in myriadS and go to increase the
stores of dust. other sources of atmospheric
| dust are found in the stream of meteOrS which
are continually plunging into the earth's atmos-
..trIt It1VO I'M