day--yes, and all day
long--before you can hope to do anything like those.

* * * * *

III. Lastly. You may perhaps wonder why, before passing to the clouds, I
say nothing special about _ground_.[233] But there is too much to be
said about that to admit of my saying it here. You will find the
principal laws of its structure examined at length in the fourth volume
of "Modern Painters;" and if you can get that volume, and copy carefully
Plate 21., which I have etched after Turner with great pains, it will
give you as much help as you need in the linear expression of
ground-surface. Strive to get the retirement and succession of masses in
irregular ground: much may be done in this way by careful watching of
the perspective diminutions of its herbage, as well as by contour; and
much also by shadows. If you draw the shadows of leaves and tree trunks
on any undulating ground with entire carefulness, you will be surprised
to find how much they explain of the form and distance of the earth on
which they fall.

Passing then to skies, note that there is this great peculiarity about
sky subject, as distinguished from earth subject;--that the clouds, not
being much liable to man's interference, are always beautifully
arranged. You cannot be sure of this in any other features of landscape.
The rock on which the effect of a mountain scene especially depends is
always precisely that which the roadmaker blasts or the landlord
quarries; and the spot of green which Nature left with a special purpose
by her dark forest sides, and finished with her most delicate grasses,
is always that which the farmer ploughs or builds upon. But the clouds,
though we can hide them with smoke, and mix them with poison, cannot be
quarried nor built over, and they are always therefore gloriously
arranged; so gloriously, that unless you have notable powers of memory
you need not hope to approach the effect of any sky that interests you.
For both its grace and its glow depend upon the united influence of
every cloud within its compass: they all move and burn together in a
marvellous harmony; not a cloud of them is out of its appointed place,
or fails of its part in the choir: and if you are not able to recollect
(which in the case of a complicated sky it is impossible you should)
precisely the form and position of all the clouds at a given moment, you
cannot draw the sky at all; for the clouds will not fit if you draw one
part