ber of original articles, relating principally to American science. In fact, the quantity of matter expressly written for this Journal, either original or compiled, is very little less, in proportion than is contained in most of the European Journals of Science. The limited means which the Editors felt themselves authorized to risk upon this undertaking and the uncertainty of the degree of support they should meet with, have prevented them from procuring so abundant and prompt a supply of European publications as they wished. The embarrassment they have laboured under in this particular has been considerable, and they are confident that their Journal is capable of being made far more valuable than it has been, should public patronage be sufficient to enable them to devote the necessary funds to this object. The patronage they have received in this immediate neighbourhood, has been flattering, and has been of itself nearly sufficient to meet the necessary expenses of the work. But at a distance, little progress has been made the subscription has advanced slowly, if at all, and without a more extensive support, it is impossible that the work should become so interesting or so useful, as it is capable of being made. While, therefore, it is their intention, at all events, to proceed with a second volume of the Journal, they solicit the attention and patronage of their countrymen in order that they may be enabled to make it more worthy of public favour and more deserving of encouragement. Boston, May 1st, 1824. ART. XIII.-Remarks on the Insensibility of the Eye to certain Colours. By JOHN BUTTER, M. D., F. L. S., M. W. S. &c. &c.; Resident Physician at Plymouth. In a Letter to Dr. Brewster. [Edin. Phil. Jour.] . MY DEAR SIR, KNOWING how much you have directed your attention to the subject of optics, and that every variation connected with the ordinary phenomena of vision is interesting to you, I transmit, without farther apology, the particulars of the following case, which my friend, Dr Tucker of Ashburton, Devon, has lately made known to me in the instance of his own son: About two years ago, Mr Robert Tucker, who is now aged 19, and the eldest member of a family of four children, discovered that he was unable to distinguish several of the primitive colours from each other. He was employed in making an artificial fly for fishing, intending to have constructed the body of the fly with silk of an orange colour, whereas he used that of a green. When the error was pointed out to him by his younger brother, he could not believe it, until it was confirmed by other persons. Threads of orange and green silk were then twisted round his finger, and he could not perceive any difference in them, but thought them to be the same coloured thread twisted several times. This circumstance led to a trial of his powers for distinguishing other colours, and the following are the results which have been ascertained, taken correctly by frequent repetition, and confirmed by the trials made in my presence. Many of the leading or primitive colours, he neither knows when they are shown, nor remembers after they have been pointed out to him. Certain colours are confounded with each other. Orange he calls green, and green colours orange; red he considers as brown, and brown as red; blue silk looks to him. like pink, and pink of a light blue colour; indigo is described as purple. The seven prismatic colours seen in the Spectrum, are described in the following manner: COLOURS. 1. Red, mistaken for 2. Orange, 3. Yellow, generally known, but sometimes taken for 4. Green, mistaken for 5. Blue, 6. Indigo, 7. Violet, So that the yellow colour alone is known to a certainty. The colours were shown to him on silk, on feathers, and in Syme's book of colours, with uniform result. Red and brown colours appear the same, as well as green and orange, blue and pink, and indigo and purple. With the exception of black or white objects, which he seldom mistakes, all colours are by him divided into three classes, viz. Class 1st, includes red and brown. 2d, 3d, blue, pink, indigo, violet, and purple. * He can generally say, with certainty, to which of these three classes any colour belongs, but he mistakes one colour for another. A difference in the shades of green he can distinguish, though not the green colour itself from the orange. Soldiers' scarlet coats appear red. Grass looks green. The colours of horses are quite unknown to him, except a white or black horse. A bay, a chesnut, and a brown horse, is described of the same colour. The colours of the rainbow or of the moon, appear nearly the same, being twofold; at least, two distinct colours only are seen, which he calls yellow and blue. A blue coat, however, he can distinguish from a black, but this circumstance may be owing to the metal buttons in the one coat, and not in the other; and a yellow vest is always known to him. By day, he called carmine red, lake red, and crimson red, purple, in Werner's book of colours by Syme; but by candle-light this error was detected, and the colours were called red with a tinge of blue. Black, which is the negation of all colour, could not be distinguished by him from a bottle-green colour, in one instance, though the difference was quite obvious to myself. Black, white, and yellow bodies are, however, recognised with tolerable certainty; though the shades of white, which again is but the beam of all colours, are not distinguishable. The shades of green can be distinguished from each other, as already stated, though none of them are known from orange. Duck-green, he called a red, and sap-green, an orange colour. If he closed one eye and looked with the other, the results were not altered. His health has been good. This defect has not sprung from disease, it bears no relation to nyctalopia *It is remarkable that green, which is the softest of colours, and composed of yellow and blue, should be mistaken for orange on every substance except on grass. or amaurosis only in its probable seat; it is natural, not morbid. Description of Eyes.-Mr R. Tucker's eyes appear to be very well formed, being oblate spheroids with corneæ, neither remarkably convex nor flat. Irides light ash-colour. His vision is exceedingly acute. It has been frequently exemplified in finding bird's nests, in shooting small birds, and in ieading minute print at a short or long distance. Light appears to him as light. He sees the forms of surrounding objects like other people at noon-day, in the twilight, and at night. In short, his sight is remarkably good in any light or at any distance. His grandfather, on his mother's side, seems not to have possessed the faculty of distinguishing colours with accuracy. General Remarks.-Physiologists may speculate in opinion, whether or not this deficiency in the faculty of perceiving colours, as exemplified in the instance of Mr R. Tucker, depended on the eye as the instrument and organ of vision, or on the sensorium to which all impressions made on the retina of the eye are referred, and in which the faculty or power of discriminating colours is supposed to reside. Vision, regarded as a sensation, is only one medium of communication, which the brain or common sensorium has with the external world. The other senses afford other media. If an eye sees objects clearly, distinctly, and quickly, vision cannot be considered defective. The faculty, whatever it may be, wheresoever it resides, of discriminating the differences between different objects, certainly is not confined to the eye. The eye is but an optical instrument, serving to the purposes of vision; the judgment exercised upon the visual sensations, is an after process, and resides not in the eye. Still, however, the construction of the visual organ, modifies the appearances of objects presented to it. All eyes do not see equally well in the same light. Nevertheless, there is a standard of vision which we call common. A difference in the vision of eyes depends, not unfrequently, on the colours of the iris and tapetum. In Albinos, the iris is red. They cannot see distinctly in the day time, because the red rays of the sun are possibly reflected, while the rest may be absorbed. It is probable that the red rays may be reflected from the iris when most closed, in Albinos, because in them there is a deficiency in the pigmentum nigrum or black coating, which covers the choroid tunic, and which being wanting, allows the rays to be more reflected and less absorbed than they are in human eyes generally, Hence the pupil is almost closed in Albinos. Red, we know, strikes the eyes most forcibly, as it is the least refrangible colour. In optics, it is proved that red bodies reflect the red rays, while they absorb the rest, and green colours reflect green rays, and possibly the blue and yellow, but absorb the rest. Still, however, the consciousness of colours does not depend on the colour of the iris, because one person having a dark iris, and another a light grey, can distinguish colours equally well; nor on the tapetum, by the same rule, though the use of this coloured matter in the eye, is not yet well made out. Herbivorous animals, as the ox, are supposed to have the tapetum in their eyes of a greener colour than carnivorous animals, in order to reflect the green colour of the pasturage: but this explanation, given by Monro primus, does not hold good, for the hare, whose tapetum is of a brownish chocolate, and the stag, which has a silvery blue tapetum inclining to a violet, is equally herbivorous with the ox. In man and apes, the tapetum is of a brown or blackish colour; in hares, rabbits, and pigs, it is of a brownish chocolate. The ox has the tapetum of a fine green-gilt colour, changing to a celestial blue; the horse, goat, and stag, of a silvery-blue changing to a violet; the sheep of pale giltgreen, sometimes bluish; the lion, cat, bear, and dolphin, have it of a yellowish-gilt pale; the dog, wolf, and badger, of a pure white, bordering on blue. The use of the tapetum and of the pigmentum nigrum, can scarcely be said to be known. We can only infer, that the tapetum, if white, might reflect all the rays and absorb none, and if black, as in man, it should absorb all the and reflect none. rays "Il est difficile," says Cuvier, "de soupconner l'usage d'une tache si eclatante dans un lieu si peu visible, Monro et d'autres avant lui, ont cru que le tapis du boeuf est vert, pour lui representer plus vivement la couleur de son aliment naturel; mais cette explication ne convient pas aux autres especes." Cuvier, Leçons d'Anat. Comp. tom. ii. 402. Birds and fishes may perceive colours as well as animals, though they have no tapetum. The vision of man is regarded the most perfect, and defective vision in old people, is sometimes produced by a deficiency of the black paint. These considerations do not, however, lead us to suppose, that the faculty of distinguishing the harmony of colours depends on the eye, any more than the concord of sounds does on the ear. The eye and the ear can be regarded only as instruments for bringing the sensorium, or thinking principle of man and animals, acquainted with |