e to the zenith, so that there is no pure blue anywhere, but a
purple increasing in purity gradually down to its point of greatest
intensity, (about forty-five degrees from the horizon,) and then melting
imperceptibly into the gold, the three colors extending their influence
over the whole sky; so that throughout the whole sweep of the heaven,
there is no one spot where the color is not in an equal state of
transition--passing from gold into orange, from that into rose, from
that into purple, from that into blue, with absolute equality of change,
so that in no place can it be said, "here it changes," and in no place,
"here it is unchanging." This is invariably the case. There is no such
thing--there never was, and never will be such a thing, while God's
heaven remains as it is made--as a serene, sunset sky, with its purple
and rose in _belts_ about the sun.

Sec. 12. The exceeding value of the skies of the early Italian and Dutch
schools. Their qualities are unattainable in modern times.

Such bold, broad examples of ignorance as these would soon set aside all
the claims of the professed landscape painters to truth, with whatever
delicacy of color or manipulation they may be disguised. But there are
some skies, of the Dutch school, in which clearness and coolness have
been aimed at, instead of depth; and some introduced merely as
backgrounds to the historical subjects of the older Italians, which
there is no matching in modern times; one would think angels had painted
them, for all is now clay and oil in comparison. It seems as if we had
totally lost the art, for surely otherwise, however little our painters
might aim at it or feel it, they would touch the chord sometimes by
accident; but they never do, and the mechanical incapacity is still more
strongly evidenced by the muddy struggles of the unhappy Germans, who
have the feeling, partially strained, artificial, and diseased, indeed,
but still genuine enough to bring out the tone, if they had the
mechanical means and technical knowledge. But, however they were
obtained, the clear tones of this kind of the older Italians are
glorious and enviable in the highest degree; and we shall show, when we
come to speak of the beautiful, that they are one of the most just
grounds of the fame of the old masters.

Sec. 13. Phenomena of visible sunbeams. Their nature and cause.

But there is a series of phenomena connected with the open blue of the
sky, which we must