one-sixth of an inch) which
corresponds to an eye-to-frame distance of eighteen inches. They give
to a high moon, if they are very careful, a quarter of an inch for
diameter. This means that the observer is about two and a half feet,
or thirty inches from the picture--nearly twice what the artist's eye
really is as he paints. And then--if painting a moon-rise or
sunset--they suddenly pretend to go to a distance of nine and a half
feet from the picture and make the moon an inch across because it is
low down, or even give the moon two inches in diameter, which would
mean that they (and those who look at the picture when hung up for
view) are observing at nineteen feet distance from the front plane or
frame of the picture. They do not alter the other features in the
picture to suit this change of distance of the eye from the frame and
there is no warning given. Certainly there is no obvious and necessary
reason for treating a picture containing a high moon as though you
were three feet from the front plane of the scene presented, and a low
moon as though you were twenty feet from that plane! The confusion
which may result in the representation of other objects when these
changes of eye-to-frame distance are made is shown by the following
simple facts. According to the simple laws of perspective, if the eye
is at thirty inches from the picture-plane or frame (as declared by a
moon drawn of a little more than a quarter of an inch broad), a post
or a man six feet high drawn on the canvas as three inches high
absolutely and definitely means that that man or post is sixty feet
away from the observer inside the picture. The height of the
represented object is the same fraction of the real object as the
eye-to-frame distance is of the distance of the observer to the real
object. If by a two-inch moon the artist has thrown you back from the
front plane of the scene to a distance of nineteen feet, then the
six-foot post or man drawn as three inches high definitely asserts
that it or he is 456 feet distant within the picture. So, too, if the
church tower which cuts the moon is really sixty feet high and is
drawn of two inches vertical measure in the picture, it is an
assertion--when the moon is represented one quarter of an inch
broad--that the church tower is 290 yards, or a sixth of a mile
distant. If, on the other hand, other things remaining the same, the
moon is drawn two inches in diameter, the church tower is now asserted
to