218 E. B. TITCHENER— ETHNOLOGICAL TESTS OF SENSATION. 



whole period of observation.^^ There is, however, a second possi- 

 bility, to which I now turn. 



(2) Geissler, working upon the chromatic limen with colored 

 papers, found that increase of the general illumination markedly de- 

 creased the limen of B, while it had no such marked effect upon the 

 limens of R and Y. I am not quite sure of the figures which should 

 be quoted for comparison ; but it appears that, for two observers, in- 

 creased illumination (natural daylight "several times as bright" as 

 the artificial daylight otherwise used) lowered the limen of B, in 

 degrees of the color disc, 



from 4.12 or 4.64 to 1.83, 

 and 



from 5.28 or 5.80 to 2.96. 



Whichever pair of larger figures we take, as a basis of comparison, 

 " the striking fact is that the limen for blue in natural light was low- 

 ered."-^ I can parallel this result by observations on colored glasses. 

 In 1890 I visited with Mr. (later Sir Francis) Galton the anthropo- 

 metrical laboratory which he had equipped at South Kensington ; and 

 among other things I worked awhile with Galton's " instrument for 

 testing the perception of differences of tint."^* My notes tell me 

 that the laboratory attendant and I " made a great hash " of our trials 

 with blue, and that Galton remarked on the gloom of the laboratory 

 as unfavorable to color work. I cannot remember that we worked 



22 The tintometer limens for the four red-insensitives are 50, 70, 80, 120. 

 Rivers thinks that the subjects with the two highest Hmens "had probably 

 some degree of weakness of the red-green sense" (R, ^z)^ and they may 

 belong to Nagel's anomalous or atypical trichromates (W. Nagel, " Ueber 

 typische und atypische Farbensinnsstorungen," Zts. f. SinnesphysioL, XLIIL, 

 1908, 299 ff.). The two blue-insensitives have limens of 50 and 60; other 

 subjects, not characterized as insensitive to blue, give 45, 60, 60, 80. These 

 high limens may be due simply to lack of practice; experience in the labo- 

 ratory shows that undergraduates are far more likely to give the name " gray " 

 to a slightly bluish gray than to a red-gray or a yellow-gray of the same 

 chroma; blue is undoubtedly like gray. These considerations modify my 

 argument in detail ; they do not affect its principle. 



23 L. R. Geissler, "Experiments on Color Saturation," Amcr. Journ. 

 Psych., XXIV., 1913, 177 f- 



24 F. Galton, " Exhibition of Instruments," etc., Journ. Anthrop. Inst., 

 August, 1889, 27 f. 



