Idaho County free press. [volume] (Grangeville, Idaho Territory) 1886-current, 1886-12-03
COLOR BLINDNESS.

some of the COIors Which Persons of De-
fective Vision Are Unable to Dis
tingu'sh.
The most frequent defect in color
Dl ndness is the inability to distinguish
red. A stinguished professor in an
English university once wore a scarlet
gown through the streets, much to the
anu sement of many who saw him. On
being asked by a friend what appeared
to him to be the color of his robe. he
answered, pointing to some evergreens
near by: ut seems to me to resemble
those rs closely as possible" The
next color most frequently mistaken for
some other is green. The Importance
of this defect is estimated by the fire.
quencv of it's occurrence. If it occurs
only once in ten thousand persons. it is
of course of less Importance than If
happening once in one hundred. Men
are more frequently affected with this
defect in vision than women. The de-
feet when il is congenital, as it is in
most of the cases under the observa-
ton of PHI sicians. is incurable. 1t is
sometimes induced by immoderate use
of tobacco or liquor AS many as one
in twenty-five of the men employed on
lines of travel are Affected by this IN
ability to d stinguish red from green.
The color-blind in case of acc dent by
travel on land or sea can not be de-
tected, because of the difficulty of
tracing the causes of the acc dent. One
thus affected can not tell a red from a
green light, but one of the lights APP
pears darker or less bright to him than
the other.
The test of color blindness is not how
well one can name colors, but how
much he sees them. If two letters be
drawn, one red and another green, on a
black ground, person who red blind
W II dlstngu sh only the green letter
and a person who is green blind would
fail to distinguish or see the green let
ter. In other words, to the first the
red color is suppressed and to the
second the green. The red bl nd will
place purple or green alongs de of
a rose color, supposing them to be the
same shade. The green blind W L con-
found the blue and the gray with the
rose color. The test for an engineer is
| hOb W udlHC COlOIS all SndQts VI COlOl
but to know red as red and green as
green. and to match red with red and
green with green of their various
>hades. Four per cent. of the fifty
thousand employees of the Pennsylvania
have been found totally color-blind
and ten per cent. more or less affected
with this defect of vision. Five per
cent of the same were found with i'm
perfect hear ng. In New York lives a
well-known an NAL painter who is en-
tirely color-bl nd. He selects his colors
not by knowing the color itself, but by
reading Their names on the tubes. He
employs usually only black brown. and
white in his work.
DIR. Jeffries, of Philadelph a, insti-
tuted very efficient test of color blind
ness by suspending numbered skeins Of
worsted of different colors from rod
The standard colors of rose red. anC
green, with all the various shades Of
those colors. were numbered W tn the
odd numbers. All other colors were
numbered w tn the even numbers. The
persons examined for -blindnes.
were invited to match the shades of thu
three named before as a standard, anC
if anv so named were among thos,
nnmbered with the even numbers it wa,
seen at once that they were unable t.
d stingu sh colors.-From Recent Pa
per by DR.. George s. Aunsen.