Chapter I: The Cloud-Balancings

§ 1. We have seen that when the earth had to be prepared for the habitation of man, a veil, as it were, of intermediate being was spread between him and its darkness, in which were joined, in a subdued measure, the stability and insensibility of the earth, and the passion and perishing of mankind.

But the heavens, also, had to be prepared for his habitation.

Between their burning light,--their deep vacuity, and man, as between the earth's gloom of iron substance, and man, a veil had to be spread of intermediate being;--which should appease the unendurable glory to the level of human feebleness, and sign the changeless motion of the heavens with a semblance of human vicissitude.

Between earth and man arose the leaf. Between the heaven and man came the cloud. His life being partly as the falling leaf, and partly as the flying vapor.

§ 2. Has the reader any distinct idea of what clouds are? We had some talk about them long ago, and perhaps thought their nature, though at that time not clear to us, would be easily enough understandable when we put ourselves seriously to make it out. Shall we begin with one or two easiest questions?

That mist which lies in the morning so softly in the valley, level and white, through which the tops of the trees rise as if through an inundation--why is _it_ so heavy? and why does it lie so low, being yet so thin and frail that it will melt away utterly into splendor of morning, when the sun has shone on it but a few moments more? Those colossal pyramids, huge and firm, with outlines as of rocks, and strength to bear the beating of the high sun full on their fiery flanks--why are _they_ so light,--their bases high over our heads, high over the heads of Alps? why will these melt away, not as the sun rises, but as he descends, and leave the stars of twilight clear, while the valley vapor gains again upon the earth like a shroud?

Or that ghost of a cloud, which steals by yonder clump of pines; nay, which does _not_ steal by them, but haunts them, wreathing yet round them, and yet--and yet, slowly: now falling in a fair waved line like a woman's veil; now fading, now gone: we look away for an instant, and look back, and it is again there. What has it to do with that clump of pines, that it broods by them and weaves itself among their branches, to and fro? Has it hidden a cloudy treasure among the moss at their roots, which it watches thus? Or has some strong enchanter charmed it into fond returning, or bound it fast within those bars of bough? And yonder filmy crescent, bent like an archer's bow above the snowy summit, the highest of all the hill,--that white arch which never forms but over the supreme crest,--how is it stayed there, repelled apparently from the snow--nowhere touching it, the clear sky seen between it and the mountain edge, yet never leaving it--poised as a white bird hovers over its nest?

Or those war-clouds that gather on the horizon, dragon-crested, tongued with fire;--how is their barbed strength bridled? what bits are these they are champing with their vaporous lips; flinging off flakes of black foam? Leagued leviathans of the Sea of Heaven, out of their nostrils goeth smoke, and their eyes are like the eyelids of the morning. The sword of him that layeth at them cannot hold the spear, the dart, nor the habergeon. Where ride the captains of their armies? Where are set the measures of their march? Fierce murmurers, answering each other from morning until evening--what rebuke is this which has awed them into peace? what hand has reined them back by the way by which they came?

§ 3. I know not if the reader will think at first that questions like these are easily answered. So far from it, I rather believe that some of the mysteries of the clouds never will be understood by us at all. "Knowest thou the balancings of the clouds?" Is the answer ever to be one of pride? "The wondrous works of Him which is perfect in knowledge?" Is _our_ knowledge ever to be so?

It is one of the most discouraging consequences of the varied character of this work of mine, that I am wholly unable to take note of the advance of modern science. What has conclusively been discovered or observed about clouds, I know not; but by the chance inquiry possible to me I find no book which fairly states the difficulties of accounting for even the ordinary aspects of the sky. I shall, therefore, be able in this section to do little more than suggest inquiries to the reader, putting the subject in a clear form for him. All men accustomed to investigation will confirm me in saying that it is a great step when we are personally quite certain what we do _not_ know.

§ 4. First, then, I believe we do not know what makes clouds float. Clouds are water, in some fine form or another; but water is heavier than air, and the finest form you can give a heavy thing will not make it float in a light thing. _On_ it, yes; as a boat: but _in_ it, no. Clouds are not boats, nor boat-shaped, and they float in the air, not on the top of it. "Nay, but though unlike boats, may they not be like feathers? If out of quill substance there may be constructed eider-down, and out of vegetable tissue, thistle-down, both buoyant enough for a time, surely of water-tissue may be constructed also water-down, which will be buoyant enough for all cloudy purposes." Not so. Throw out your eider plumage in a calm day, and it will all come settling to the ground: slowly indeed, to aspect; but practically so fast that all our finest clouds would be here in a heap about our ears in an hour or two, if they were only made of water-feathers. "But may they not be quill-feathers, and have air inside them? May not all their particles be minute little balloons?"

A balloon only floats when the air inside it is either specifically, or by heating, lighter than the air it floats in. If the cloud-feathers had warm air inside their quills, a cloud would be warmer than the air about it, which it is not (I believe). And if the cloud-feathers had hydrogen inside their quills, a cloud would be unwholesome for breathing, which it is not--at least so it seems to me.

"But may they not have nothing inside their quills?" Then they would rise, as bubbles do through water, just as certainly as, if they were solid feathers, they would fall. All our clouds would go up to the top of the air, and swim in eddies of cloud-foam.

"But is not that just what they do?" No. They float at different heights, and with definite forms, in the body of the air itself. If they rose like foam, the sky on a cloudy day would look like a very large flat glass of champagne seen from below, with a stream of bubbles (or clouds) going up as fast as they could to a flat foam-ceiling.

"But may they not be just so nicely mixed out of something and nothing, as to float where they are wanted?"

Yes: that is just what they not only may, but must be: only this way of mixing something and nothing is the very thing I want to explain or have explained, and cannot do it, nor get it done.

§ 5. Except thus far. It is conceivable that minute hollow spherical globules might be formed of water, in which the enclosed vacuity just balanced the weight of the enclosing water, and that the arched sphere formed by the watery film was strong enough to prevent the pressure of the atmosphere from breaking it in. Such a globule would float like a balloon at the height in the atmosphere where the equipoise between the vacuum it enclosed, and its own excess of weight above that of the air, was exact. It would, probably, approach its companion globules by reciprocal attraction, and form aggregations which might be visible.

This is, I believe, the view usually taken by meteorologists. I state it as a possibility, to be taken into account in examining the question--a possibility confirmed by the scriptural words which I have taken for the title of this chapter.

§ 6. Nevertheless, I state it as a possibility only, not seeing how any known operation of physical law could explain the formation of such molecules. This, however, is not the only difficulty. Whatever shape the water is thrown into, it seems at first improbable that it should lose its property of wetness. Minute division of rain, as in "Scotch mist," makes it capable of floating farther,[1] or floating up and down a little, just as dust will float, though pebbles will not; or gold-leaf, though a sovereign will not; but minutely divided rain wets as much as any other kind, whereas a cloud, partially always, sometimes entirely, loses its power of moistening. Some low clouds look, when you are in them, as if they were made of specks of dust, like short hairs; and these clouds are entirely dry. And also many clouds will wet some substances, but not others. So that we must grant farther, if we are to be happy in our theory, that the spherical molecules are held together by an attraction which prevents their adhering to any foreign body, or perhaps ceases only under some peculiar electric conditions.

§ 7. The question remains, even supposing their production accounted for,--What intermediate states of water may exist between these spherical hollow molecules and pure vapor?

Has the reader ever considered the relations of commonest forms of volatile substance? The invisible particles which cause the scent of a rose-leaf, how minute, how multitudinous, passing richly away into the air continually! The visible cloud of frankincense--why visible? Is it in consequence of the greater quantity, or larger size of the particles, and how does the heat act in throwing them off in this quantity, or of this size?

Ask the same questions respecting water. It dries, that is, becomes volatile, invisibly, at (any?) temperature. Snow dries, as water does. Under increase of heat, it volatilizes faster, so as to become dimly visible in large mass, as a heat-haze. It reaches boiling point, then becomes entirely visible. But compress it, so that no air shall get between the watery particles--it is invisible again. At the first issuing from the steam-pipe the steam is transparent; but opaque, or visible, as it diffuses itself. The water is indeed closer, because cooler, in that diffusion; but more air is between its particles. Then this very question of visibility is an endless one, wavering between form of substance and action of light. The clearest (or least visible) stream becomes brightly opaque by more minute division in its foam, and the clearest dew in hoar-frost. Dust, unperceived in shade, becomes constantly visible in sunbeam; and watery vapor in the atmosphere, which is itself opaque, when there is promise of fine weather, becomes exquisitely transparent; and (questionably) blue, when it is going to rain.

§ 8. Questionably blue: for besides knowing very little about water, we know what, except by courtesy, must, I think, be called Nothing--about air. Is it the watery vapor, or the air itself, which is blue? Are neither blue, but only white, producing blue when seen over dark spaces? If either blue, or white, why, when crimson is their commanded dress, are the most distant clouds crimsonest? Clouds close to us may be blue, but far off, golden,--a strange result, if the air is blue. And again, if blue, why are rays that come through large spaces of it red; and that Alp, or anything else that catches far-away light, why colored red at dawn and sunset? No one knows, I believe. It is true that many substances, as opal, are blue, or green, by reflected light, yellow by transmitted; but air, if blue at all, is blue always by transmitted light. I hear of a wonderful solution of nettles, or other unlovely herb, which is green when shallow,--red when deep. Perhaps some day, as the motion of the heavenly bodies by help of an apple, their light by help of a nettle, may be explained to mankind.

§ 9. But farther: these questions of volatility, and visibility, and hue, are all complicated with those of shape. How is a cloud outlined? Granted whatever you choose to ask, concerning its material, or its aspect, its loftiness and luminousness,--how of its limitation? What hews it into a heap, or spins it into a web? Cold is usually shapeless, I suppose, extending over large spaces equally, or with gradual diminution. You cannot have, in the open air, angles, and wedges, and coils, and cliffs of cold. Yet the vapor stops suddenly, sharp and steep as a rock, or thrusts itself across the gates of heaven in likeness of a brazen bar; or braids itself in and out, and across and across, like a tissue of tapestry; or falls into ripples, like sand; or into waving shreds and tongues, as fire. On what anvils and wheels is the vapor pointed, twisted, hammered, whirled, as the potter's clay? By what hands is the incense of the sea built up into domes of marble?

And, lastly, all these questions respecting substance, and aspect, and shape, and line, and division, are involved with others as inscrutable, concerning action. The curves in which clouds move are unknown;--nay, the very method of their motion, or apparent motion, how far it is by change of place, how far by appearance in one place and vanishing from another. And these questions about movement lead partly far away into high mathematics, where I cannot follow them, and partly into theories concerning electricity and infinite space, where I suppose at present no one can follow them.

What, then, is the use of asking the questions?

For my own part, I enjoy the mystery, and perhaps the reader may. I think he ought. He should not be less grateful for summer rain, or see less beauty in the clouds of morning, because they come to prove him with hard questions; to which, perhaps, if we look close at the heavenly scroll,[2] we may find also a syllable or two of answer illuminated here and there.

FOOTNOTES:

[1] The buoyancy of solid bodies of a given specific gravity, in a
given fluid, depends, first on their size, then on their forms.

First, on their size; that is to say, on the proportion of the
magnitude of the object (irrespective of the distribution of its
particles) to the magnitude of the particles of the air.

Thus, a grain of sand is buoyant in wind, but a large stone is not;
and pebbles and sand are buoyant in water in proportion to their
smallness, fine dust taking long to sink, while a large stone sinks
at once. Thus, we see that water may be arranged in drops of any
magnitude, from the largest rain-drop, about the size of a large pea,
to an atom so small as not to be separately visible, the smallest
rain passing gradually into mist. Of these drops of different sizes
(supposing the strength of the wind the same), the largest fall
fastest, the smaller drops are more buoyant, and the small misty rain
floats about like a cloud, as often up as down, so that an umbrella
is useless in it; though in a heavy thunder-storm, if there is no
wind, one may stand gathered up under an umbrella without a drop
touching the feet.

Secondly, buoyancy depends on the amount of surface which a given
weight of the substance exposes to the resistance of the substance it
floats in. Thus, gold-leaf is in a high degree buoyant, while the
same quantity of gold in a compact grain would fall like a shot; and
a feather is buoyant, though the same quantity of animal matter in a
compact form would be as heavy as a little stone. A slate blows far
from a house-top, while a brick falls vertically, or nearly so.

[2] There is a beautiful passage in _Sartor Resartus_ concerning this
old Hebrew scroll, in its deeper meanings, and the child's watching
it, though long illegible for him, yet "with an eye to the gilding."
It signifies in a word or two nearly all that is to be said about
clouds.