The daily dispatch. [volume] (Richmond [Va.]) 1850-1884, 1879-09-24
l9itl,nlo,td pisllnteh
=..,nyrspaY. SEPTEMBER a, 1870.
Coior.R7iDGness.

~ review in Scribner for October OF
Satfries's recent book on this subject
VI .ske these interesting facts:
We n.Iismereu's plan for.the determination OF
ho'n,indness does not consain anything
cee;;,i either as regards the materials {co-
o'ssuafee ylin %ools) or the method tcompari-
tafte me colors and shades, independent
son son., VI names). Seebeck had used the ma
Of OLE iM and the method years before. What
..ss .!nen did was 10 shorten the method
n n;.nnn, lcssenng its accuracy, and thus
W. /, Dyact;cal for extensive examine
Emn. nv Secbeck's method more than
,.' p",, persons could not be examined
~ hour. whereas, according to Holm
IL MAN hundred or more can be ex-
ssrn;,ed in that time. Holmgren's methed
:" oS follows: 4 Jorge assortment OF Berlin
,,no,s Of all eolors and shades OF color l0o
% oN1 skeinsl Is spread before the person 10
Up examined, and O bright-green Skein lhot
;rc,in,ns 10 either yellow or hue) Is iald
aside as a sample" He IS then toid 10
>cIrc, from the pile those skeins which APP
,,nor 70 him of the same color but OF differ
on, sbades-i. e., lighter or darker. Ii ne
con make this selection properly he Is not
coIor.bl,nG. II, however. lie lays by the
..semDle" other colors, particularly brown
mr. cray. he is color-biind. This examine
tion, when tue person examined IS one
~ ordinary intelligence, is made IN min
,ta, or even less time, and the question OF
rnIor-blindncss is settled. Practically, this
i sufficient. but il 1t is desired to know the
,,o,,,craar color 10 which the individual is
Wind another examination must be made.
4. nrcsent three kinds OF co!or-blindncss
ar, recognized, corresponding to the three
.o.rolled primary colorS-red, green, and
violet or blue. As violet, or blue-blndnesS, is
exceedingly rare, an examination as to the
first two is sufficient, particularly as they
are the two col0rs most important in pracli-
cal life. In this second examination n pure
purple is laid aside as 4 " sample" and the
Icr<on examined Is told to select shades ap-
nearing to him like it. Ii he selects Srays
or greens be is grecn-blird; il violet Oh
blue he is rcd-blind; il orange or vel.
low he i vioct-blind.
The results OF examinations made
in various parts OF the world to this
time. aggrcgaling over 100000, show that
nm, male IN abont every twenty-five whites
a ncr cent is color-b!ind in greater or less
decree. 1t would seem from limited num-
her OF examinations OF Jews by Cohn and
Nacnus in Brc<lau, that this race is more
subject to color blindness than Christians,
and from some examinations by DR.. Swan
II. Burnett. OF Washington, OF the negroes
in The public schools OF that city (3,050 in
numherl. il appears that that race is less al
icr,cd viii. the coIor-blindncsS than the
white race. The female sex is rarely affect
cd-only about one in iour hundred. As a
rule the defect is coDgenital, though 1t Is
sometimes acquired through disease, and it
j. Frequently hereditary.
The importance OF a true sense OF color
to railway and marine employees, where the
lives OF many persons depend on proper
discrimination between 4 red (danger) and
= green t>aiety) signal is apparent, 1t is
evident that Il law should be passed requi-
ring an examination OF such employees in
respect to their color-senSe. DR.. JcifrieS
has succeeded in having such 4 law passed
lv the Massachusetts Legislature. and it is
to he hoped, in the interest OF humanity,
that the matter will be pressed to the same
result in all the States, or in our National
Congress.