ON ACCIDENTAL OR SUBJECTIVE COLORS. 251 



views, which are more pertinent to our purpose. M. Seebeck has distributed 

 the daltonians into two classes : the first comprises the individuals who are 

 rather mistaken in the degree of the coloring than the nature of the color. The 

 tints which they more or less confound are: the bright orange and pure yellow; 

 the deep orange, the clear yellowish or brownish green and the yellowish brown ; 

 the pure clear green, the grayish brown and flesh-color ; the rose-colored red 

 and the green rather bluish than yellowish ; crimson and deep green and chest- 

 nut-brown ; bluish green and dull violet ; lilac and bluish gray ; azure and bluish 

 gray and lilac. Their perception is very defective as regards the specific im- 

 pression of colors in general, and especially so for red and consequently green, 

 which they discriminate but little or not at all from gray. Yellow is the color 

 of which their appreciation is most correct, although they often see less di£fer- 

 ence between this color and the appearance of colorless bodies than is discerned 

 by eyes of normal conformation. The second division comprises persons who 

 confound bright orange with greenish yellow, brownish yellow and pure yellow ; 

 deep orange with brown yellow and grass green ; red and deep olive green ; 

 vermilion and deep brown, carmine and blackish green ; carnation, grayish 

 brown, and bluish green ; dull bluish gray and brownish gray, yellowish rose- 

 color and pure gray, deep rose with lilac, azure and gray passing into lilac ; 

 crimson and violet, deep violet and deep blue. They have but a feeble percep- 

 tion of the least refrangible rays ; it is in this that their most strikingly dis- 

 tinctive characteristic consists, and on this rests chiefly the distinction between 

 the two classes. It explains not only why the individuals of the second class, 

 like those of the first, confound red with dark green, but will account moreover 

 for all the differences which separate them, if it be remarked that the absence 

 of the orange rays occasions much affinity between blue, colorless light, and 

 even red. 



We know that as the obscurity becomes greater the least refrangible rays 

 disappear first froln the light of the atmosphere, and that from this more prompt 

 disappearance arise the changes of color observed under such circumstances. 

 If, therefore, the defect of sensibility for these rays characterizes the daltonism 

 of the second class, the daltonians of the first class should find themselves, 

 during the approach of darkness, nearly in the same condition with those of the 

 second. Towards evening, M. Seebeck presented to one of the first class of 

 daltonians two series of colors, of one of which he judged very correctly, while 

 he was constantly mistaken as regarded the other ; in proportion as the obscur- 

 ity increased, the first series betrayed him more and more into error, while the 

 second was better and better appreciated ; when the obscurity became consid- 

 erable, the second series was that on which he was no longer deceived, while 

 he erred completely in regard to the first. He could soon no longer distinguish, 

 like the daltonians of the second class, by the light of day, the blue sky from 

 the rosy red ; finally, he judged not more correctly of the colors of the second 

 series: the red paper which, by day, appeared to him too dazzling, then ap- 

 peared too dark. Subjected to the same tests, the eyes of the daltonians of 

 the second class acted quite differently : the obscurity had at first produced on 

 them no effect ; their judgments respecting the second series of colors were in- 

 variable ; more and more correct, they agreed with those of the first daltonian, 

 especially in the impression that, under tiie influence of the growing obscurity, 

 the red paper had become darker. Obscurity then reduces to the second class 

 the daltonians of the first ; reciprocally, by a bright orange green placed before 

 the eye the daltonians of the second would be reduced to the first class. In 

 these observations M. Seebeck has presented us with some very original views, 

 and has proved himself here, as in all his labors, a profound and skilful 

 physicist. 



Classification of Dr. Szokalski. — M. Szokalski comprises under the name 

 cJiromatp-pseudopsy — formed from three Greek words •^pw/j.a, color; ^eudoq, 



