Dust cloud

“ It is probable, however, that while you were perfectly familiar with the idea of the atmosphere carrying clouds of dust, on occasions, you never thought of the atmosphere being constantly loaded with dust, which is constantly being deposited, and constantly renewed. This sunbeam has made the fact visible. It has lighted up the tiny cloud of dust, which we see to be restlessly whirling. ”

“ A dust-storm is invariably the forerunner of a cool change. First a lurid cumulus obscures the sky, angry clouds of dust form, and willy-willies rise suspiciously in the direction whence the storm approaches. The day becomes dark, and in a few minutes the goldfields town is hidden as by an impenetrable cloud. It is impossible to see more than a few feet ahead. ”

“ He continues to describe the dust storm as follows:—“Some of them come on with great rapidity, as if at the rate of forty to sixty miles an hour. They occur at all hours, oftentimes near sunset.
The sky is clear and not a breath moving: presently a low bank of clouds is seen in the horizon, which you are surprised you did not observe before; a few seconds have passed, and the cloud has half filled the hemisphere, and there is no time to lose—it is a dust storm—and helter-skelter every one rushes to get into the house to escape being caught in it. ”

“ Such a dust cloud will be no longer attracted toward the sun, but will be driven away by its light. It will be like the comets' tails, which consist chiefly of dust, radiate from the nuclei, and are always turned away from the sun. ”

“ The cloud of dust, in fact, rises from the whole column, and extends way back up the Rosebud, and even as I am wondering how far it can be seen, my eye is attracted by just as thick a cloud around the point, apparently coming up the valley. ”

“ There is dust, dust, and thunder in it and singing over it like a high wind blowing. The horses and men are floating in it. It is closing in over the prairie, but the ring of boxes looks empty and is still.
“No! It is not empty and still. It puffs smoke all around and goes out in a cloud and a roar. The cloud gets higher and does not go away. The roaring does not stop. It is like a great blanket ripping. ”

“ Rapidly this bears down upon us, increasing in size as it comes, till it reaches towards the zenith, blotting out the storm clouds, mountains, and plain with a pall as dense as a curtain. For those in the cloud the wind is burning hot [5] ; the fine dust covers the face, cakes the eyelashes and even the teeth. ”

“ Dust essential to Fogs.—Nearly ten years ago John Aitken, of Edinburgh, proved experimentally that the presence of dust was essential to the formation of fog and cloud. He connected two receivers, one containing common air, the other air freed from dust by passing through cotton-wool, with a boiler. ”

“ A constant procession of vehicles passes my house, and to-day each one approaches in a cloud of dust. The air is gray with suspended particles of dirt. The wind carries the successive clouds, and they roll up against the houses like breakers on the beach. Windows and doors are loose enough to let dust sift in. When a door opens, the cloud enters and lights on rugs and carpets and curtains. Any ledge collects its share of dust. The beating of carpets and rugs disturbs the accumulated dust of many months. ”

“ In our ordinary atmosphere there can be no clouds without dust. A dust-particle is the nucleus that at a certain humidity becomes the centre of condensation of the water-vapour so as to form a cloud-particle; and a collection of these forms a cloud.
This condensation of vapour round a number of dust-particles in visible form gives rise to a vast variety of cloud-shapes. There are two distinct ways in which the formation of clouds generally takes place. Either a layer of air is cooled in a body below the dew-point; or a mass of warm and moist air rises into a mass which is cold and dry. ”

“ When the March wind comes blustering down the street, rudely dashing a cloud of dust in our faces, we are uncomfortable and out of patience. We duck our heads and cover our faces, but even then we are likely to get a cinder in one eye, to swallow germs by the dozens, and to get a gray coating of plain, harmless dust. We welcome the rain that lays the dust, or its feeble imitation, the water sprinkler, that brings us temporary relief. ”

“ Without atmospheric dust, we should not have the glorious cloud scenery which we at present enjoy. We should have no haze in the atmosphere, we should have no twilight. Darkness would come as soon as the sun passed below the horizon.
The relative humidity of the air has a great effect on the dust by increasing the size of the particles of water vapor and so increasing the haze. The number of dust particles rapidly decreases with the amount of moisture present. ”

“ The floating dust motes of the air are factors of great meteorological importance. They are the nuclei upon which the water vapor of the air condenses. Dense clouds of volcanic dust act as a screen preventing much of the sun’s heat from reaching the earth. The dust particle is the normal nucleus for the cloud particle. The flying, or windblown dust, though a highly important physiographic agent, is not a factor of importance in meteorology. ”

“ If, then, air, which always has dust particles in it, containing all or nearly all the water vapor it can hold, is cooled to a distinctly lower temperature, a corresponding amount of condensation will take place on each dust mote, and the countless droplets thus formed will appear as a fog or cloud of greater or less density. ”

“ One supposes the Indians might have learned the use of smoke signals from these dust pillars as they learn most things direct from the tutelage of the earth. The air begins to move fluently, blowing hot and cold between the ranges. Far south rises a murk of sand against the sky; it grows, the wind shakes itself, and has a smell of earth. The cloud of small dust takes on the color of gold and shuts out the neighborhood, the push of the wind is unsparing. Only man of all folk is foolish enough to stir abroad in it. ”

“ Every bit of steam shrinks, when chilled, to a much more minute particle of water. The liquid particles thus produced form a kind of water dust of exceeding fineness, which floats in the air, and is called a cloud. ”

“ Turning, now, our attention to the atmosphere, we find that at nearly all times, and everywhere within two miles of the surface, and probably much higher still, it contains, in every cubic inch, thousands of dust particles coming from fires, from plants, from the dry earth as caught up by winds, and from still other sources. Much of this dust is excessively fine and settles down with extreme slowness. It serves, as already explained, as nuclei about which the myriads of cloud droplets are formed. ”

“ In the forenoon the clouds begin to gather and pile up in dark billowy masses that end in showers during the afternoon and evening. But not every rain cloud brings rain. Clouds of this character often look very threatening, but all their display of thunder and lightning is only bluff and bluster and ends in a fizzle with no rain. After such a demonstration the clouds either bring wind and a disagreeable dust storm, or, if a little rain starts to fall, the air is so dry that it evaporates in mid air, and none of it ever reaches the earth. ”

“ The dust-clouds, lighted up by the evening sun, show the exact direction of the storm; some are of an inky black, others gray, and in the distance they can be seen dashing up against one another, and forming, as it were, a series of hills and valleys; yet there is scarcely a leaf moving, and all nature seems hushed. ”

“ Hence when the atmosphere is heavily charged with dust particles that have become moisture laden, as they will in a humid atmosphere, and therefore relatively bulky, we see the sun as a fiery red ball. We know, too, that this dust has much to do with rainfall for, as was first proved many years ago by the physicist Aitken, cloud particles, and, therefore, rain, will not, under ordinary conditions, form in a perfectly dust-free atmosphere, but will readily form about dust motes of any kind in an atmosphere that is sufficiently damp. ”

“ These dust-particles are not the motes that we see in the path of a sunbeam; for, when common air is passed through a flame, these motes disappear, but the air still remains a good medium for fogs. It is a finer kind of dust which furnishes the fog and cloud nuclei. The products of combustion are fog producers, and especially the vapor from the burning of sulphur. ”

“ We may thus define a fog as a surface cloud sufficiently thick to cause hindrance to traffic. It will be a thick mist if the cloud consists of water particles, a thick haze if it consists of smoke or dust particles which would be persistent even in a dry atmosphere. ”

“ The dust clouds are often so dense that they hide the sun and all landmarks by which the traveler can guide his way. But have any of us ever seen the winds pick up much dust from the green fields where the vegetation protects the surface? ”

“ Passing the earth on their return they will increase the amount of dust-clouds careering round it; and these will be further increased by the action of the ultra-violet rays of the sunlight causing particles to shoot radially away from the earth when the negative charge of the upper atmosphere has reached a certain amount, which particles, although starting sunward, will be swept back to the earth with the oncoming streams. ”

“ Here you find the hot sink of Death Valley, or high rolling districts where the air has always a tang of frost. Here are the long heavy winds and breathless calms on the tilted mesas where dust devils dance, whirling up into a wide, pale sky. Here you have no rain when all the earth cries for it, or quick downpours called cloud-bursts for violence. ”

“ Our wildest phase of the west wind here at Coniston is 'swallow-like' with a vengeance, coming down on the lake in swirls which spurn the spray under them as a fiery horse does the dust. On the other hand, the softly ascending winds express themselves in the grace of their cloud motion, as if set to the continuous music of a distant song. ”

“ Every little drop of rain has a grain of dust in the middle. The colors of the sunset, too, are due partly to dust. Not only that, but colors of the sunset vary as the particles of dust which reflect the rays of light, are enveloped by water vapor.
"A piece of dust, without an envelope of water, is smaller than one with a little wetness around it. When more water vapor gathers around the piece of dust, the drop becomes bigger. When the sunset is red, it is a sign that it is shining on very small bits of dust, or that the condensation of water vapor into rain has not advanced very far. ”

“ Each gleaming point of light is like a seed Dilating swiftly to coiling fires. Each cloud becomes a rapidly dimming face, Each hurrying face records its strange desires. ”

“ Clouds of dust swirled around us; we had to turn our backs and cover our eyes with our hands, for the dust blinded us. There was a streak of lightning across the sky, then came a heavy clap of thunder. ”

“ Occasionally, when the heat seemed to have reached its highest pitch, the bearer would appear, and ask leave to roll up the outside verandah chicks, as a storm was coming. The air felt thick and heavy, and the breathless stillness was overpowering. In a moment all was changed, and a raging tempest was upon us. A dust-storm is a terrible sight—the whole atmosphere a red mass, a whirlwind of dust, and all as dark as night around. ”

“ It is a desolate place, and is made more so by the clouds coming down and completely damping us and the view. It is rather dreary jogging along with these human ponies in a dense mist, out of which loom palely the foremost bearers, when, as suddenly as we came into it, the fog lifted, leaving us the most beautiful cloud effects of white filmy vapours, trailing low down on the mountain side, with a patch of blue sky just beginning to show, and the sun shining up there behind those opaque masses of cloud and mist, making them appear so fleecy and transparent. ”

“ The world-wide distribution of atmospheric dust is a remarkable phenomenon. As the blue colour of the sky is universal, the whole of the higher atmosphere must be pervaded by myriads of ultra-microscopical particles, which, by reflecting the blue rays only, give us not only the azure vault of heaven, but in combination [ 256] with the coarser dust of lower altitudes, diffused daylight, the grand forms and motions of the fleecy clouds, and the 'gentle rain from heaven' to refresh the parched earth and make it beautiful with foliage and flowers. ”

“ Venus had to be right.
It was! A blast of wind struck us, and dust, swirling everywhere. We'd discovered there's no such thing as a sand storm—it's really dust—so we'd taken pains making things look right. Sand dunes were carefully cemented in place; dust rippling over gave the proper illusion.
Oddly shaped rocks, dimly seen, strengthened the impression of wind-abraded topography. Rocks were reddish, overlain by smears of bright yellow. Lot of trouble placing all that flowers of sulfur, but we postulated a liquid sulfur-sulfur dioxide-carbon dioxide cycle. ”

“ For several years back I have been zealous for the examination of all substances of the nature of dust which fall to the surface of the earth with rain or snow, and I have proved that a portion of them is of cosmic origin. This inconsiderable fall of dust is thus of immense importance for the history of the development of our globe, and we regard it, besides, with the intense interest which we inevitably cherish for all that brings us an actual experience regarding the material world beyond our globe. ”

“ In a whirlwind of dust raised by an impetuous wind, however confused it may appear to our eyes; in the most dreadful tempest excited by opposing winds, which convulse the waves, there is not a single particle of dust or of water that is placed by chance that has not its sufficient cause for occupying the situation in which it is, and which does not rigororously act in the mode it should act. ”