to be level, produce on his eye the impression of a
slope. It requires repeated and close attention before he detects this
fact, or can be made to feel that the lines on his paper are false. And
the Chinese, children in all things, suppose a good perspective drawing
to be as false as we feel their plate patterns to be, or wonder at the
strange buildings which come to a point at the end. And all the early
works, whether of nations or of men, show, by their want of _shade_, how
little the eye, without knowledge, is to be depended upon to discover
truth. The eye of a Red Indian, keen enough to find the trace of his
enemy or his prey, even in the unnatural turn of a trodden leaf, is yet
so blunt to the impressions of shade, that Mr. Catlin mentions his once
having been in great danger from having painted a portrait with the face
in half-light, which the untutored observers imagined and affirmed to be
the painting of half a face. Barry, in his sixth lecture, takes notice
of the same want of actual _sight_ in the early painters of Italy. "The
imitations," he says, "of early art are like those of children--nothing
is seen in the spectacle before us, unless it be previously known and
sought for; and numberless observable differences between the age of
ignorance and that of knowledge, show how much the contraction or
extension of our sphere of vision depends upon other considerations than
the mere returns of our natural optics." And the deception which takes
place so broadly in cases like these, has infinitely greater influence
over our judgment of the more intricate and less tangible truths of
nature. We are constantly supposing that we see what experience only
has shown us, or can show us, to have existence, constantly missing the
sight of what we do not know beforehand to be visible: and painters, to
the last hour of their lives, are apt to fall in some degree into the
error of painting what exists, rather than what they can see. I shall
prove the extent of this error more completely hereafter.

Sec. 7. The difficulty increased by the variety of truths in nature.

Be it also observed, that all these difficulties would lie in the way,
even if the truths of nature were always the same, constantly repeated
and brought before us. But the truths of nature are one eternal
change--one infinite variety. There is no bush on the face of the globe
exactly like another bush;--there are no two trees in the forest whose
boughs bend into