The mirror. (Stillwater, Minn.) 1894-1925, 1904-12-08


Illusions, are lacking. The reader. theref
the Omission.-EDITOR.
Paper Read Before the Chaotauqua Circle.
4 S instruments of communica-
~ tion our sense organs are the
sole mediums thru which we
are enabled to adjust ourselves
to our environment, and it goes with
out saying that the present we'll devel-
oped state of these organs is but the
product of an almost interminable
series of evolution.
While the eye was not one of the
first of the organs of sense to undergo
development, it is, nevertheless, the
most highly developed, and altho re-
markably we'll adjusted for the func-
tions it has to perform even the So
called normal eye possesses certain
surprisingly defective characteristics.
The average person entertains an
erroneous belief that the sense of sight
is infallible; that the eyes present per-
ceptible objects to the mind with un-
failing accuracy, and some persons
have become so impressed with the
truthfulness of their visual organs
that they are inclined to discredlt all
other sources of knowledge, and hesi-
tate to accept anything as true which
they cannot see. They not infre-
quently manifest their presence by the
assertion "Pm from Missouri-you
must show me" and adopt for their
standard of life the adage that "seeing
is believing"
While it is an accepted fact that &C.
curate observation is the fundamental
method of all true knowledge, it is no
less fact that many centuries ago it
was discovered that under certain con-
ditions even the eyes were capable of
deception. This discovery was devel-
oped and emphasized to such an extent
that the certainty of any and all knowl-
edge was interrogated and scepticism
of the EXTREMIST sort became prevalent
Abnormal and transitOry as such condi-
tions were, it is, nevertheless, not little
disquieting when actual experience
conclusively demonstrates that our
eyes can and oftentimes do deceive
us.
Series two of our class curriculum
so exhaustively and-I may we'll add
so DELIGHTFULLY."- treats the subject un-
der discussion that l cannot hope to do
more than stimulate your interest in
the pursuit of so fascinating study.
Without attempting to pursue the in
terminable lengths of scientific
channels or to employ the syllabifica-
tions of technical terminology let us
consider-briefy-some of the more
common illusions of perception.
One of the most common of the rec.
ognized optical illusions occurs in con.
nection with the length of lines.
Authorities tell us that linear distances
and surfaces are judged by the amount
of eye movement necessary to look
from one extremity of the object of
regard to the other. AS certain cir
cumstances facilitate this movement
of the eye, while others retard it, it
logically follows that objects over
which the eye can move unrestrictedly
are underestimated, while those over
which the eye moves with more or less
difficulty are overestimated.
Exhibit one shows two figures pos
sessing horizontal lines Of an equal
length, even tho there appears to be
quite disparity. An explanation is
to he found in the fact that the arrow
heads on the figure designated by the
letter ga" are turned in, and arrest the
eye movement before the termination
of the line is actually reached, whereas,
those on "B" are turned outwards and
solicit the eye to go beyond the end of
the line proper.
Pedestrians are inclined to estimate
the distance traversed by the amount
of effort expended in covering the
distance, and those of us that have
had occasion to walk on railroad ties
know that the distance actually
covered was considerably less than
the distance which we thought we
had covered.
In traversing railroad ties, each tie
must be taken into consideration and