The morning news. [volume] (Savannah, Ga.) 1887-1900, 1895-12-05
THE HUMAN EYE.
hut Few Eyes Are usually Perfect.
How They Are Aided by Glasses.

hut Few Eyes Are usually Perfect.
How They Are Aided by Glasses.
From the Boston Journal OF Commerce.
The human eye is no doubt one Of the
most perfect contrivances that Dame Nat
ure ever took an interest in, and vet wa
find that there is quite a business going
on in the way of assisting this wonderful
organ by the aid of glasses. No eve is
perfect IN every respect, and the mechanic
who is blessed with sight true enough 10
plumb line without the aid of a level
should surely be thankful What is done
in an opera glass by the aid of two lenses
moved in and out to bring the object in
focus, Is all accomplished in the eye with
one simple lens made SO elastic that it can
be easily hattened down by muscules
drawing outward from all sides around
IT'S outer edges, and in this way accom-
modates itself for objects both near and
at distance. AS the elasticity of this
lens is impaired with age, 1t is no wonder
that assistance is needed to help bring
. me rays OF Ilght 70 focus: Not only
this but we frequently hear Of mechanics
who have good eyesight and need no as
sistance as far as near sight or far sight
Is concerned, yet at working at the bench
with file the edges of the work will run
together, and things in general will look
out of square, when there is no earthly
reason for this appearing so. The trouble
IN THIS case is all due to the refracting
surfaces of the eye not being perfectly
spherical Just notice how true and
spherical the surfaces are of maRnifv-
ing glass, and how clear and distinct
every ray of light will be brought to a
focus, and then imagine what the effect
would be IL that same lens were ground
egg-shaped, or left in the same condition
as the surface on the bowl of a spoon
A mechanic with a distortion Of this kind
in his eyesight is not to blame for tipping
his head or turning around and looking
cornerways to get a better squirt at an
object. Glasses for this trouble are easily
obtainable, ground in one direction as
though simple window glass, but left con-
cave or convex, as the case calls in the
other, so as to bring up the eyesight in
the direction ii is impaired Evidently
DR.. Huntington took the hint from some
of his astigmatic patients when he studied
up the fitting lens. Take any pair of opera
glasses and arrange the glasses next to
the eye so that they viii tilt or move
about as though on a universal Joint, and
they can easily be brought in a position
where the view win be equally clear in all
directions. This front lens. that Is, con-
cave on both sides, can tilt far enough to
true up the worst case Of compound as
tigmatism. though at first ii may seem
impossible. II Is like cutting on a section
OF cone on q slant. II makes a true
ellipse whatever direction the section is
made, and an eliipse tilted in the direc-
ton OF its major axes soon appears In a
true circle when the tilt has reached the
proper point. This fitting the eye-piece OF
an opera glass Is an experiment than can
easily be made. and IL will be surprising
how few viii need the glass just square
across when they work down 10 a nne
point, and what a number will tilt IL an
Tor one eye and over to one side for the
other, Glasses are inconvenlent but me-
chanic must keep his vision where Il be-
longs u nc Intends 70 DO good work.