Bauhaus-Universität Weimar

Some new apparatus. 
105 
A suitable arrangement of tbe colors gives direct simultaneous 
comparisons of reds, greens, and grays of different shades. The 
well-known confusion by color-blind persons of dark greens with 
reds, greens with gray, etc., are exactly imitated, and the instrument 
gives a decisive test for color-blindness. Its peculiar advantage, 
however, lies in the fact that it presents reds, greens, and grays 
simultaneously in a large number of different shades of intensity. 
The light of a green lantern, as it appears to a color-weak person at 
different distances, is simulated by the red behind the different grays ; 
at the same time a white light is also changed. The color-weak per¬ 
son to whom weak green is the same as gray (white at a distance) is 
utterly confused and thinks that the weakened green is gray (white) 
and the dark gray is green. 
The actual test is performed in the following manner : The tester 
is held toward a window, but not in the bright sunlight, at about 2^ 
feet from the person tested. The operator begins with any chance 
position of the glasses, and asks the person tested to tell the colors 
seen through the three glasses, Nos. 1, 2, and 3. He answers, for 
example, “No. 1 is dark red ; No. 2 is gray ; No. 3 is green.” The 
operator records from the back of the tester the letters indicating 
what glasses were actually used. Suppose he finds that A, D, and G 
were opposite the glasses Nos. 1, 2, and 3 he records : A 1, dark red ; 
D 2, gray; G 3, green. The disk is then turned to some other posi¬ 
tion, the colors are again named, and the operator records the names 
used. For example, the result might be : “No. 1 is dark green ; No. 
2 is white ; No. 3 is red.” and the record would read: G 1, dark 
green ; J 2, white ; A 3, red. Still another record might give ; J 1, 
dark gray ; A 2, red ; D 3, medium gray. Similar records are made 
for all combinations. Of course, the person tested knows nothing 
concerning the records made. The blank thus filled out is forwarded 
to the chief inspector for railway or marine service. A comparison 
with a table containing the true colors for each position determines 
whether the test has been passed or not. 
The records can be taken by any one, and, on the supposition that 
the record has been honestly obtained and that the instrument has 
not been tampered with after leaving the central office, the compari¬ 
son is likewise mechanical. There is none of the skillful manipula¬ 
tion required in the wool test and none of the uncertainty attaching 
to its results. The only instruction given to the subject is, “Name 
the colors ” ; the results render the decision with mechanical cer¬ 
tainty.
        

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