Savannah courier. (Savannah, Tenn.) 1885-1979, 1888-10-18
N.HOW NATURE CONJURES.
Prof Proctor Disproves the Adage
that Seeing Is Believing"
Queer Optical Deceptions and Explana-
tions of Some of Them-The Refraot-
Ing Power of the Air-Mistakes in
Color and Shape.


last written by Prof. Richard A. Proc
tor for the Philadelphia Press previous
to his recent death by yellow fever at
New York hospital.
o"Seeing is believing" says the old
proverb, but seeing is deceiving"
would be nearer the mark. We are
deceived by false impressions even
when we know the real state Of the
case, so that nature may IN some sense
be compared with conjurer who ex-
plains the trick he is about to play,
yet deceives the eye as perfectly as
though We knew nothing about the
manner of his performance. We know
that the handkerchief which we gave
hin to experiment upon has not been
cut in half, yet we saw him cut it
in half; we know he has not pounded
our gold watch in a mortar, yet that is
what we saw him do.
Here is nature about to perform her
daily conjuring trick of making the
sun, as he sets, look larger than he
really is. Isay nothing of his looking
out of shape, because nature uses APP
paratus to produce that illusion, and
the eye really does see correctly. But
she makes the sun look swollen and
huge without apparatus, though again
and again we find her clever perform
ance explained in that way. The
kindly instructive persons who wrote
"Sandfords and Mertons" for the con-
fusion of intelligent childhood, care
fully explain that it is the refracting
power of the air which enlarges the
setting sun, even as the refracting
power of water in glass bottle en-
larges letters seen through it. But the
refracting power of the air has nothing
to do with the apparent enlargement
of the sun. 1t does affect the suns APP
parent size, but the other way,
making him look smaller not larger
in just such degree as it apparently
congresses him from globe to an
egg. Nature simply takes us in when
she makes us believe that the
setting sun looks larger than the sun
in the midheavens Nature deceives us
by making us think the sun in the
midheaven looks smaller than when
near the horizon. Perhaps the reader
thinks the statements identical. But
they are not We are nearer the truth
when we judge the suns size as he
nersrs the horizon than when we esti-
mate it from his appearance high
above that circle. The reason is OBJ
yioes, When the sun is low we can
see by the aspect OF the landscape
that he is much farther away than yon-
der house or hill or tree than when he
is actually on the horizon. We see
that he is behind those objects, and
thus we can not imagine him to be
merely foot or yard in diameter, be-
tween which lengths lie all the esti-
mates of the suns diameter, which
the mind unconsciously forms when
he is high in the sky. So he seems to
be much larger when low.
But just here the thoughtful reader
will perhaps urge that the eye ought
still to be able to judge whether the
image of the sun in the visual field is
really no larger when he is low. The
eye, however, knows nothing about
its visual field. The mind judges of
what the eye sees in quite other ways.
Here is simple experiment to show
this:
In good black ink draw a capital
INDEPENDENTLY round o in strong
black type on white card. Now, sit
ting facing wall of uniform tint, hold
or fix the card steadily in an upright
position at about arms length and
contemplate that black o as steadily
as possible, 'while one with moderate
haste may count hundred" Now let
the card drop and look at the wall
with as little interruption in the time
and as little change in the diameter OF
vision as possible. There is seen as
usual the complementary image of the
letter, but it has grown much larger.
II. for instance, the o is an inch in
diameter and the wall is twelve times
ms far away as the card had been, the
letter seen will be apparently foot in
diameter. The mind is not able to
..,,,ds ;ts<,lf that the latter has mt
grown suddenly larger. Yet in reality
the image in the visual field is pre-
cisely the same now as 1t had been be
fore. The mind is simply deceived by
the effect of distance-the same OBJ
iect seen of the same apparent size
but supposed to be at a greater dis
lance, is judged to be larger.