loss silk; looking as if each knot were a little swathe
or sheaf of lighted rain.

23. Aqueous vapour or mist, suspended in the atmosphere, becomes
visible exactly as dust does in the air of a room. In the shadows, you
not only cannot see the dust itself, because unillumined, but you can
see other objects through the dust, without obscurity; the air being
thus actually rendered more transparent by a deprivation of light.
Where a sunbeam enters, every particle of dust becomes visible, and a
palpable interruption to the sight; so that a transverse sunbeam is a
real obstacle to the vision--you cannot see things clearly through it.
In the same way, wherever vapour is illuminated by transverse rays,
there it becomes visible as a whiteness more or less affecting the
purity of the blue, and destroying it exactly in proportion to the
degree of illumination. But where vapour is in shade, it has very
little effect on the sky, perhaps making it a little deeper and greyer
than it otherwise would be, but not, itself, unless very dense,
distinguishable or felt as mist.

24. Has the reader any distinct idea of what clouds are?

[15]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 splendour 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 vapour 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 ret