g (if I may coin a
word) of the different points of the figure during the different hours
of the day and the different days of the week deep into the canvas,
may be necessary.

I am speaking of outdoor, landscape work, for which only four hours,
at most, either in the morning or in the afternoon, can be utilized.
In this four hours nature keeps comparatively still long enough for
you to caress her with your brush, and if you would truly express what
you see, your work must be finished in that time. I can quite
understand that to the ordinary student this is a paralyzing
statement, but let us analyze it together for a moment and I think
that we shall all see that if it were possible for a human hand to
obey us as precisely as a human eye detects, the results on the canvas
would be infinitely more valuable, first, because the sun never stands
still and the shadows of one hour are not the shadows of the next; and
second, because this moving of the sun is affecting not only the mass
but the composition of the picture, one mass of buildings being in
light at ten o'clock and again in shadow at eleven. It is also
affecting its local color, the yellow of the afternoon sunlight
illumining and graying the silver-blue of the shadows, thus weakening
the force of positive shadows scattered through the composition. Of
course, to be really exact, there is only one moment in any one of the
hours of the day in which any one aspect of nature remains the same,
but since we are all finite we must do the best we can, and four
hours, in my experience, is all that a man can be sure of.

We have, of course, the next day to continue in, but then the
landscape has changed. That delicate, transparent, gauzy cloud screen
that softened the sky light was, under the northwest wind of
yesterday, a clear, steely gray-blue, and the sun shining through it
made the sunlight almost white and the shadows a neutral blue; to-day
the wind is from the south and a great mass of soft summer clouds,
tea-rose color, drift over the clear azure, each one of which throws
its reflected light on every object over which they float. The half
you painted yesterday, therefore, will not match the half you must
paint to-day, and so if you will persist in working on your same
canvas you go on making an almanac of your picture, so apparent to an
expert that he can pick out the Monday, Tuesday, and Wednesday as you
daily progressed. If you should be fortunate enough to work un