be eight times as far off, or about a mile and a third. Very
generally these facts are not considered by painters. They represent
the low moon (or sun) big because the erroneous mental impression is
common to all of us that it _is_ big--that is, bigger, much bigger,
than the high moon or sun, and they do not follow out the consequences
in perspective of the pictorial increase of the moon's apparent
diameter.

If we could ascertain why it is that the low moon produces a false
impression of being bigger--as a mere disc in the scene--than does the
high moon, we might be able to discover how an artist could produce,
as Nature does, an impression or belief in its greater size whilst
keeping it all the time to its proper size. The explanation of the
illusion as to the increased size of the sun's or moon's disc when
low, given by M. Flammarion and other astronomers, is that the low sun
or moon is unconsciously judged by us as an object at a greater
distance than the high moon or sun. This is due to the long vista of
arching clouds above and of stretching landscape or sea below when the
sun or moon is looked at as it appears on or near the horizon. The
illusion is aided by the dulness of the low moon and the brightness
(supposed nearness) of the high moon. Being judged of (unconsciously)
as further off than the high moon, the low moon is estimated as of
larger size although of the same size. This is, I believe, the correct
explanation of the illusion. When one gazes upwards to the sky, a
small insect slowly flying across the line of sight sometimes is
"judged of" as a huge bird--an eagle or a vulture--since we refer it
to a distance at which birds fly and not to the shorter distance to
which insects approach us. It seems that it would be possible for the
painter, by carefully studying actual natural facts and introducing
their presentation into his picture, to produce the impression of
greater distance, and therefore of size, into a quarter-inch moon
placed near the horizon. He is not compelled for want of other means
to "cut the difficulty" and paint a falsely inflated moon which shall
brutally and by measurement call up the illusion of increased size. I
reproduce here (Pl. V) an interesting drawing which shows how such
illusions of size _can_ be produced. It is none the worse for my
purpose because it is an advertisement by the well-known firm who
have kindly lent it to me. The three figures represented in black
are all of t