The Columbia herald. [volume] (Columbia, Tenn.) 1850-1873, 1873-01-10
The Eve.

The Eye.
There is no optical instrument maker
who does not succeed in constructing
an apparatus much more perfect in
MANY points than the eye-that marvel
lous organ, which we are inclined to re-
gard as the masterpiece of vital and or
ganic architecture, on account of the
great service it renders to man.
This sense of sight, which is SO far
reaching that it gives us the power to
penetrate infinite space and apprehend
the universe, at the same time makes us
familiar with the minutest objects; this
sense, which is the freest and most I'M
circumscribed in its actions-for our
sense of touch is limited by the length
of our arms, hearing to a few thousand
feet, the senses of smell and taste hay
ing still greater hmitations-this sense,
I say, acts through an agent apparently
so imperfectly adapted to its purpose,
that recent investigations stand amazed
at the idea how by it we receive any in
telligible impressions. That we do is
an evidence of the independence of the
mind, and of it's power to make useful
these necessary and imperfect means of
contact with the outer world, and proves
the necessity of educating this sense to
quick and precise perceptions in order
to correct its faults and perfect the
work which Nature has designedly left
imperfect.
The eye has the defect of what in
physics is called the alteration of
sphericity;" that is, the rays that pass
through the centre of lens have COM
mon focus, but rays which pass certain
distance from the centre do not converge
at the same point, but pass beyond.
The nearer they come to the circumfer-
ence, the greater the focal distance, if
the lens is vigorously spherical. In a
good optical instrument, this defect is
scarcely perceptible, the rays being CEN
tralized by fattening the lens. Again,
the eye is not spherical, but has an clip
tica1 curve. This was for some time
thought to be an advantage, but the con-
trary is the truth. And this curve is
not even well centred, that is, placed
symmetrically to the visual axis like a
lens, but is charged and twisted in eve
ry direction. From this results what
has been called the astigmatism of the
eye, which consists in not being able to
see at the same distance a vertical line
with the same distinctness as one that
is horizontal. This recently discovered
phenomenon has attracted the attention
of all occulists, as it sometimes consti-
tutes real disease of the eye. Again,
the retina of the eye has spots where it
is entirely blind to impressions of light.
But is this eye, which is unsymmetri-
cal, badly centred, blind in spots, at
least perfectly translucid? Not at all.
The cornea and crystalline lens of the
eye are not absolutely hmpid, as APP
pears when examined through an in
intense blue or violent light, which rem
ders it fuorescent. This phenomenon
is due to the traces of q substance anal
ogous to quinine, body which possess
es in the highest degree the property of
fiuorescence, that is, of emitting a light
of it's own, under the excitement of blue
or violet lights. The crystalline lens,
itself, is not of a homogeneous compost
ton, but has crystalline structure of
six branches. This is the cause of the
stars appearing to us with rays. All at
tempts to explain this phenomenon
were vain, until it was found to be in
the visual organ itself. It is for this
reason that the crescent of the moon,
when it is very thin, seems to be double
or triple to some persons.
These facts are enough to show any
one how prone the unframed eye must
be to error and self-deception, and that
seeing is not physical but mental act.
In infancy, the eye is aided by the
hands or touch to acquire experience of
the nature and consistency of things;
later in life, the eye asserts it's superior
ity by instructing the hands to perform
ingenious and cunning work. The two
senses seem thus to continue mutually
to assist and act upon each other.
Touch lends to light material aid and
support. The eye refnes and gives in
telligence to the material sense of touch,
so that, when sight is wanting, touch
takes its place and performs its duties
The eye in its direct and steady look
embraces but a small compass of actual
sight; in fact, we clearly see but small
point, which comes just in the focus of
the eye; and it is owing to a quick, vi
bratory movement of the eye that we
are able to see large extents apparently
at the same time.