The work we have already gone through together has, I hope, enabled you
to draw with fair success, either rounded and simple masses, like
stones, or complicated arrangements of form, like those of leaves;
provided only these masses or complexities will stay quiet for you to
copy, and do not extend into quantity so great as to baffle your
patience. But if we are now to go out to the fields, and to draw
anything like a complete landscape, neither of these conditions will any
more be observed for us. The clouds will not wait while we copy their
heaps or clefts; the shadows will escape from us as we try to shape
them, each, in its stealthy minute march, still leaving light where its
tremulous edge had rested the moment before, and involving in eclipse
objects that had seemed safe from its influence; and instead of the
small clusters of leaves which we could reckon point by point,
embarrassing enough even though numerable, we have now leaves as little
to be counted as the sands of the sea, and restless, perhaps, as its
foam.

In all that we have to do now, therefore, direct imitation becomes more
or less impossible. It is always to be aimed at so far as it _is_
possible; and when you have time and opportunity, some portions of a
landscape may, as you gain greater skill, be rendered with an
approximation almost to mirrored portraiture. Still, whatever skill you
may reach, there will always be need of judgment to choose, and of speed
to seize, certain things that are principal or fugitive; and you must
give more and more effort daily to the observance of characteristic
points, and the attainment of concise methods.

I have directed your attention early to foliage for two reasons. First,
that it is always accessible as a study; and secondly, that its modes of
growth present simple examples of the importance of leading or
governing lines. It is by seizing these leading lines, when we cannot
seize _all_, that likeness and expression are given to a portrait, and
grace and a kind of _vital_ truth to the rendering of every natural
form. I call it _vital_ truth, because these chief lines are always
expressive of the past history and present action of the thing. They
show in a mountain, first, how it was built or heaped up; and secondly,
how it is now being worn away, and from what quarter the wildest storms
strike it. In a tree, they show what kind of fortune it has had to
endure from its childhood; how troublesome trees have co