The account of Dr. Dalton’s own peculiarity of vision by himself, offers considerable interest. He says, speaking of flowers: “With respect to colours that were white, yellow, or green, I readily assented to the appropriate term; blue, purple, pink, and crimson appeared rather less distinguishable, being, according to my idea, all referable to blue. I have often seriously asked a person whether a flower was blue or pink, but was generally considered to be in jest.” He goes on further to say, as the result of his experience: “1st. In the solar spectrum three colours appear, yellow, blue, and purple. The two former make a contrast; the two latter seem to differ more in degree than in kind. 2nd. Pink appears by daylight to be sky-blue a little faded; by candlelight it assumes an orange or yellowish appearance, which forms a strong contrast to blue. 3rd. Crimson appears muddy blue by day, and crimson woollen yarn is much the same as dark blue. 4th. Red and scarlet have a more vivid and flaming appearance by candlelight than by daylight” (owing probably to the quantity of yellow light thrown upon them). As anecdotes concerning this curious defect of colour vision, we may quote also the following: “All crimsons appeared to me (Dr. Dalton) to be chiefly of dark blue, but many of them have a strong tinge of dark brown. I have seen specimens of _crimson claret_ and _mud_ which were very nearly alike. Crimson has a grave appearance, being the reverse of every showy or splendid colour.” Again: “The colour of a florid complexion appears to me that of a dull, opaque, blackish blue upon a white ground. Dilute black ink upon white paper gives a colour much resembling that of a florid complexion. It has no resemblance to the colour of blood.” We have a detailed account of the case of a young Swiss, who did not perceive any great difference between the colour of the leaf and that of the ripe fruit of the cherry, and who confounded the colour 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 the ash gray colour of quick-lime light green. On a very careful comparison of polarized light by the same individual, the blue, white, and yellow were seen correctly, but the purple, lilac, and brown were confounded with red and blue. There was in this case a remarkable difference noticed according to the nature and quantity of light employed; and as the lad seemed a remarkably favourable example of the defect, the following curious experiment was tried. A human head was painted, and shown to the colour-blind person, the hair and eyebrows being white, the flesh brownish, the lips and cheeks green. When asked what he thought of this head? the reply was, that it appeared natural, but that the hair was covered with a nearly white cap, and the carnation of the cheeks was that of a person heated by a long walk.