1450 



VISION. 



for red; pink appeared sky blue by daylight, lastly, the remaining O'OOS' of red appeared to 



but assumed an orange or yellowish appear 

 ance by candle light. Dalton believed that 



him of a red difficult to define. By 'refracted 

 light the results were nearly the same, thirty - 



the peculiarity in his vision was caused by the seven plates of glass exhibiting only four 



vitreous humour of his eyes having a blue 

 tint : to this point reference will hereafter be 

 made. 



According to Professor Wartmann, the 

 following are the most common confusions of 

 colour, ranged in order of their frequency : 



1. Deep red with deep blue. 



Indigo with violet. 



Deep blue with violet. 



Bright orange with bright yellow. 

 ^ 5. Deep brown with deep green. 



Dark blue with indigo. 



Bright brown with bright green. 



Dark red with dark green. 



Rose with bright blue. 

 10. Dark orange with dark yellow. 



Bright red with bright green. 



Deep yellow with dark green. 



Dark brown with black. 



Bright red with bright blue. 

 15. Bright yellow with bright green. 



Bright red with bright yellow. 



Dark red with black. 



Dark red with dark brown. 



Dark green with violet. 

 20. Dark red with dark yellow. 



Dark red with violet. 



Bright yellow with bright brown. 



Bright blue with violet. 

 25. Dark red with dark grey. 



Dark red with indigo. 



Rose with violet. 



Dark blue with dark grey. 



Dark green with indigo. 

 30. Rose with dark blue. 



Rose with indigo. 



Dark green with dark grey. 



Bright orange with bright green. 



White with faint green. 



Putting aside the differences in the bril- 

 liancy of the tints, it is found that the follow- 

 ing numbers express how many times each of 

 those tints is proportionally seen without 

 error. 



Red - 

 Orange - 

 Yellow - 

 Green - 



- 37 



- 12 



- 100 



- 59 



Blue 



Indigo - 

 Violet - 



- 100 



- 



- 



different colours m various intensities. 



When examined by polarized light, it seems 

 that on the one hand he did not appreciate 

 the equality of intensity of two complementary 

 colours as did ordinary vision ; but he found 

 a total and abrupt difference when colours 

 passed at once from the finest red to very 

 rich deep blue, a distinction far from being 

 marked to others. 



His visual organ was unable to perceive the 

 different mixtures of red which accompany 

 blue to make it pass into purplish violet. 

 This precise circumscription of the consti- 

 tutive domain of a colour is a fact which, in 

 the opinion of Professor Wartmann, was new 

 and worthy of being remarked. 



Whilst a series of these experiments with 

 polarised light were going on, the sun, which 

 had been obscured, suddenly shone out, and 

 D - declared that the colours imme- 

 diately assumed a different tint to his sight, 

 all reddening in a sensible manner, so that 

 he called red that which he had before named 

 green and ill-defined blue, whereas the Pro- 

 fessor saw no other change in the colours 

 than an increase of their brilliancy and strength. 

 Wartmann then submitted the patient to 

 experiments to ascertain his perception of the 

 complementary colours, and the result showed 

 that although his eyes were not insensible to 

 them, the colours which appeared to him 

 complementary were not the same as those so 

 regarded by the normal eye. The Professor 

 then painted a human head, giving to each 

 part a complementary colour. Thus the hair 

 and eyebrows were white, the flesh brownish, 

 the sclerotica black, the lips and cheeks green. 

 When asked what he thought of the head, 

 D - replied that it appeared to him na- 

 tural, that the hair was covered with a white 

 cap little marked, and that the carnation of the 

 cheeks was that of a person heated by a long 

 wa'k. 



are a crtain numb of ases of in 



Wartmann has given* a very interesting u 



account of his experiments on the vision of f ens ; blht y to colours which have been quoted 

 Louis D - . This individual did not per- by all writers on the subject. W. .h.ll th. 

 ceive any great difference between the colour 

 of the leaf and that of the ripe fruit of the 

 cherry ; he confounded that of a sea-green 

 paper with the scarlet of a riband placed close 

 to it. The flower of the rose seemed to him 



greenish blue, and he called the ash colour 

 of quick lime light green. The appearances 



We shall there- 

 fore content ourselves with merely referring 

 to them*, describing a few well marked and 

 uncommon instances less generally known. 

 Dr. Boys de Loury -f- has published the 



particulars of a M. H , who was obliged, 



on account of his defective sight, to aban- 

 don the profession of a dyer. His principal 



VI UW*Wn 11411^ 414111L. 11 V.V'U* J 1^ SJI'IV^Ul Cl I I I . V Q . .. _, ' - .... - ., ,, 



presented by a solar spectrum were as follows, c lour * as > el ^ The brilliant yellow of 



* . J trio onii/>/-kf oriH rloon r\i/-*riTn r\r tn*a stnAovuftil 



the coloured bands, brilliant and distinct, 



extended a length of about 0-102'. D 



perceived four colours only, blue, green, yel- 

 low and red. He limited the blue part exactly 

 to the space occupied by the violet, indigo and 

 blue : he called the green and yellow bands, 

 less an interval of 0'002' towards the orange, 

 green ; he called that band of 0'002 / , and a 

 fraction of the red 0'012' in breadth, yellow; 



* Taylor's Scientific Memoirs, vol. iv. p. 173. 



the apricot and deep brown of the chesnut 

 were only distinguished as varieties of shade. 

 AH dark hues were called black ; scarlet ap- 



* Cases of achromatopsy are detailed as follows: 

 Phil. Trans, vol. Ixvii. p. '260, vol. Ixviii. p. Gil ; 

 Edinb. Phil. Trans, vol. x. 253 ; Spurzheim Phren- 

 ology, 3d ed. p. 276 ; Combe's Syst. of Phrenology ; 

 Trans. Phren. Society, p. 222 ; Trans. Med. Chir. 

 Society, vol. vii. p. 477, vol. ix. p. 359 ; Glasgow 

 Med. Journal, vol. ii. p. 12 ; Edinb. Phil. Journal, 

 vol. vi. p. 135. 

 , f Revue Me'dicale, Nov. 1843. , 



