The daily morning journal and courier., 1901-10-24

| AL HldHy or the ODSerVatorleS scat l tered throughout the world, not only are sunsets thus relegated to certain | definite classes, but, in order to give the record a scientific value still fur Y ther particulars concerning the sunset | are added. Thus the position of the colors as regards their position in the | SKY, or IS regards altitude and azi- | muth, as the terms are, are observed; While the time at which the colors
 were seen and any increase or decrease in the brilliance of the coloring would also be considered worthy of a place in the records In all such systematic observations the time when the colors
 were at their brightest, and when they faded away, would be noted, and, fur ther, in order to make the record quite | complete, the time of sunset or sunrise
 would also be registered.
 Now the color in tho sky may, as it were, be painted on the clouds, or on the hazy air, or on the open sky itself, As regards the latter the color that is
 most conspicuous is, of course, the blue,
 and in seeking for the origin of this
 tint it will be found that the search leads to an explanation of many of the
 other colors. On looking up into the sky on a cloudless, sunny day. when
 the swallows, perhaps, are flying so
 high that they appear but as tiny
 specks in the dome of blue,r it seems
 almost impossible to think of the at
 mosphere as being otherwise than per
 fectly clear and translucent. It is,
 however, in reality charged with mi
 mute dusty particles, which have al-
 ways been found in myriads, whenever
 the atmosphere has been tested either
 over the open sea or at the top of high
 mountains. There is an ingenious in
 strument, indeed, by which the number
 of these atoms of dust in any given
 quantity of air may be counted, and
 by it's aid samples of air in many diff ferent parts of the world and at differ ent seasons of the year have beenana-
 lyzed, and the atoms counted. The sources from which this atmospheric dust is obtained are large. From the land, and more especially from deserts dust is continually rising, and the dust so raised is carried by the winds to ali parts. Spicules of salt, too, leap from the sea in myriads and go to increase the stores of dust. Other sources of at mospheric dust are found in the stream of meteors which are continually plunging into the earths atmosphere, their combustion also resulting in at mospheric dust Volcanoes are again important distributors of dust. A ciga- rette smoker casts some four billion dusty atoms into the air at every puff; while the shaking of door mats and other similar operations constantly serve to launch a never failing stream of dusty particles into the air. These particles of dust, it will be seen, are the agents principally responsible for tinting the atmosphere blue and for Altering out the gorgeous hues of a sunset.
 In the lower strata of the atmos- phere the coarser particles of dust not only scatter the waves of light. but they also reflect them, so that at these lower levels the blue tint is diluted by white light, and is accordingly not so intense as when seen, say, from the top of a high mountain. At this elevation only the finer varieties of dust are floating. and there is little reflection Of the light but much scattering, and hence it is here that the blue attains it greatest intensity. Tn that part of the skv nearest the sun the rays of light come in a direct line to the eye of the observer. and the scattering Of the light does not appear so great as when one looks across the path of the beams and it is due to this circumstance that the sky near the sun is not of so in- tense blue as portions of the sky fur ther away A similar kind of thing happens in respect of the clouds, where dust readily accumulates, and, reflect ing the light, produces their brilliant whiteness. At the edges of the clouds, | moreover. the atoms of dust are busily | engaged in refracting the beams of light, and to this cause IS due that brilliant fringe of brightness which so often adorns many of the largest | clouds. Not only, therefore, does the | atmosphere dust filter out of the blue | light that tints the sky, but it also fla | bricates the pigments that color the clouds. effects which can most readily | he observed in contemplating the glo- | ries of the setting sun.-Arthur H. Bell