The beautiful red sky which has been so frequent of late, morning as well as evening, has excited much comment. The comment, however, has consisted more of description, statement of fact, theory, and wonder as to cause, rather than as to satisfactory explanation.

Facts in the case which would reveal the secret of this beautiful display of nature are not complete and numerous enough at present to establish the cause of this phenomenon on a sure basis; yet enough facts, it would seem, have been obtained to satisfy the strong mind capable of bridging over a wide expanse.

Facts in an argument are like piers to a bridge-the more we have of them, c. p., the more substantial the structure. When the facts are legion, the structure becomes a causeway, and there is no need of argument.

Argument is a bridge--the fewer the facts, the more the necessity for the bridge; the less the facts, the more argument necessary to connect the few we have, and the more skill is required to make substantial connecting links between the few solid piers (facts) that exist.

One of the queer things in connection with this is, the public have looked chiefly, if not wholly, to the astronomers for an explanation of this phenomenon, when it is not their special province to explain matters in this department of nature.

The explanation belongs to the department of meteorology, and not to astronomy. But the fact of having looked to the astronomers shows how little the world knows of meteorology and how few meteorologists there are able, ready, and willing to rise and explain in face of the opposition of the public, who seem to think that the explanation must necessarily belong to astronomy. Astronomy proper deals with the position of the earth in space and its relation to the other heavenly bodies, whether suns, fixed stars, planets, satellites, comets, or other bodies in the vast space about us. Meteorology deals with the atmosphere of the globe, in all its forms. Astronomy could be studied in the early ages; its grand facts were not wholly dependent upon the advanced condition of the mechanic arts; it could be studied even without the aid of telescopes, though telescopes have added much to its advancement. Meteorology, on the contrary, depended on the advancement of the arts and sciences; they must first be perfected ere we could know much about this branch of science. To one unfamiliar with the advancement and perfection of meteorology within the past ten years, this statement may seem strange, yet it is an undisputable fact that, prior to the establishment of the daily weather reports, the knowledge on this subject amounted to very little, and was not even worthy of being designated a science. Prior to the advent of the weather map the world was in absolute ignorance of the laws governing the atmosphere. Sure, we had had large volumes on the laws of storms, but the later revelations leave them shelved high and dry on the shores and as useless as a wreck in a similar condition; with the daily weather map before us we have no need to even open these huge volumes; they are completely circumvented, and only negative in value--to show how little was known of the subject without the full and complete facts daily collected and spread before us on the map published by the Weather Bureau.

In order to understand the color of our sky, we must understand the subject which is so immediately connected with it and its creation.

The earth is a sphere in space; generally speaking, it is composed of land and water. These are two factors; the heat that it derives from the sun forms a third factor; the three--land, water, and heat--are essential to life, at least the higher conditions of life which culminate in man. The old physical geography taught us this much, but it was not able to go further and tell us why it was cold or warm independent of the seasons; it could not explain why it was at times as warm, and even warmer, half-way to the pole than at the equator; why it was at times very warm in the extreme northeast while very cold in the Southern States; cold in the northwest when it was warm in the northeast, and warm in the northwest when cold all along the upper Atlantic seaboard; it could not forewarn us of storms. These and a host of other facts, which the weather map makes as plain as astronomy demonstrates that Jupiter is a planet, the new revelation, through the instrumentality of the perfected telegraph system, makes exceedingly plain to us if we will but seek the easily obtained information.

The principal revelations of the weather map are the facts in regard to the areas of high and low barometer, and the influence they exert upon the climate of the globe.

These conditions--high and low barometer--move on general lines from the west towards the east, or towards the rising sun, and around the world in irregular belts. The centers of low barometer are various distances apart, from a thousand to two thousand and even more miles apart--call the average about two thousand miles.

The clouds are formed from the moisture present by the action of the sun's heat. The direction of the wind is from the area of high barometer to that of low. The nearer the winds approach the center of "low" (low barometer), the more they partake of the lines of the volute curve, or curve of the sea shell or water in a whirlpool. High barometer is the atmospheric hill; low barometer is the atmospheric valley. But time at present will not permit more than these general statements; a close study of the weather map for a season will reveal the beautiful minor details.

To the reader it may seem a long way round, yet in order to fully understand the nature of the atmosphere which surrounds our globe we must pay due attention to these newly discovered physical laws.

The red sky which was so noticeable, in the fall of 1883, the astronomers have told us was due to "meteoric dust" which was produced by the volcanic eruption on the island of Java, August 27, 1883.

This "meteoric dust" they say combined with the atmosphere, followed it around the earth, and caused the beautiful redness of the sky at morning and evening. For one, I do not believe dust of any description in the atmosphere would produce such an effect.

There is nothing luminous, transparent, or delicate about dust. Dust would not remain in the atmosphere for months, it would settle in a very short time, and if thick enough in the atmosphere to obstruct the light of the sun it would be visible, discernible, to the eye, and manifest on the face of nature. Years ago, before the age of the weather map, we might have thought that the atmosphere followed the surface of the earth like the water on a grindstone, but it does not. As already seen, the wind is from the area of high barometer to that of low, and there are many of these "low centers."

From the best calculation we can make at present, there would be at least some six centers on an average between the center of the United States and the island of Java. In addition to this there would also be a number of belts of "low" centers, which would complicate the thing threefold at least. At all these different centers the winds would be blowing from all points of the compass at the same time. Such winds would not be apt to bring the "meteoric dust" from Java to the United States, either in an easterly or westerly direction. But, it is said, "dust" has been gathered.

How high from the surface of the ground has this dust been gathered--at what elevation?

There is undoubtedly a little dust in the air most of the time, but I do not think that it extends very high. Where it would be the highest and most perceptible would be on the arid plans of Africa and Asia, when the simoom is passing, or in the track of a tornado. But from the multiplicity of these storm centers and the varied winds they would produce even this dust could not travel from Java to America.

Again, all clouds, no matter how high or how low, are affected by the low centers, as the movement of clouds prove, and travel from the "high" to the "low," from and to all points of the compass. High authority gives the heights of the clouds as follows: lower clouds, 16,000 feet; upper clouds, 23,000 feet.

As all clouds, from the highest to the lowest, are affected by the centers as above referred to, it follows that if this "meteoric dust" follows the earth around, as it would have to do in order to make good this theory, it would have to travel suspended in the atmosphere above the upper clouds, or at a height of more than 23,000 feet, or at an elevation of over four miles!

Now, is it reasonable to believe that dust, however fine, will remain in the atmosphere at that elevation for over six months?

As a side argument it is suggested that the smoke of the burning woods, or few years ago in Michigan, caused as peculiar condition of the atmosphere. This extensive fire was on a day when the area of low barometer was on a high line of latitude and passing to the eastward. This naturally took the smoke, which is far lighter than dust, along with it. It mingled with the muggy condition of an extensive "low," and produced a yellowness of the atmosphere. This however was of only a few hours' duration, and was only visible in favorable localities.

Here again we see the advantage of the weather maps; but for this map we would never have been able to have satisfactorily explained the peculiar phenomenon produced by the great Michigan fire.

If the delicate redness of the sky is not caused by dust, what is it caused by?

But for the weather map, I think we should still be in the dark in regard to it.

In the first place, this redness is nothing new, only the conditions are more favorable sometimes than at others. It has always existed and always will exist, independent of earthquakes, volcanoes, etc. Nature is ever changing; the movements of the atmosphere more resemble the kaleidoscope than any thing else.

The summer and fall of 1883, the movements of "high" (high barometer) over the United States were quite central and extensive, causing this peculiar phenomenon over a wide extent of territory.

We have no information of the condition of the barometer over the other part of the world; we speak move particularly of the United States; yet if certain conditions produce certain effects here, it is quite safe to say that the same effects are produced by the same cause elsewhere.

As now well established by the map, the surface wind is from the area of high barometer to that of low--from the atmospheric hill to the atmospheric valley.

The tendency of this is to free "high" of all clouds and moisture; but then it is impossible to free "high" entirely of moisture; a little will remain, and it is just this little, which is highly rarefied, that produces the result. We look around us and above, we see little or no evidence of evaporation, yet it is the while going on. When the sun is immediately below the horizon, where it will shine horizontally through the mass of light, suspended moisture, the delicate presence of vapor heretofore unnoticed is revealed. The action of the sun's rays is the same as when illuminating a well formed cloud--it is an embodiment of the same principle, but the material is much more expanded. The particles of suspended moisture are very fine, few and far between, therefore the effect of the light upon it is more diffused and transparent. It is much like looking through a piece of window glass flatwise and endwise; flatwise we do not perceive any color; endwise, from seeing through a greater mass, the glass has a very perceptible green color.

We see the same idea also in the rising and setting sun and moon. On a clear, cloudless night, when nothing seems to interfere with the brightness of the stars, we cannot, by looking upward, perceive any moisture present in the atmosphere; but if we cast our eyes to the horizon, whereby we see through the mass of atmosphere endwise, as it were, and note the appearance of the stars there, or the rising or setting moon, we will see that the atmosphere there gives a redness to the rising body, which it does not have when it has ascended to mid-heaven. On a clear night, which is caused by the presence of the area of high barometer, the moon when in mid-heaven is of a clear, silver-white, and it is the same moon that at the horizon was a deep red. The color of the moon has not changed; it is simply the medium through which it is seen that produces the difference in color.

Occasionally, on a clear, bright ("high") night, when the moon is full, prior to rising, when just below the horizon, it will so illuminate this lower strata of atmosphere as to appear like a great fire; the moon rises red, but its deep color gradually fades as it rises, and when well up in the heavens we perceive that this deep coloring was an illusion and merely the influence of its surroundings. I never, though, knew of any one to attempt to account for this by "meteoric dust;" and yet it is an embodiment of the same principle. Place the sun where the moon is, and from its far superior abundance of light we have a much grander display.

Under no other conditions or relations of the sun and earth is it possible to have this phenomenon of the delicate red sky but when a positive area of high barometer is passing and extends over us. In order to produce this effect we must have the clear atmosphere of high barometer, when there is a minimum of moisture present. The action of the sun's rays upon this extensive area of slightly moist rarefied air is unconfined by clouds, and reaches far and wide, and produces a delicacy of color which from no other source or condition can be realized.

ISAAC P. NOYES.

Washington, D. C., 1884.