though she took kindly to the place and people, seemed to pine away latterly, and had caught the swamp-fever, from which she had no strength to recover, and died on the very day of Miss Letitia's marriage. Fosbrook could not keep the news to himself, though he at first promised to do so; but in the general excitement it seemed to affect nobody in the Hall, not even Elva, which Mrs. Fosbrook thought an additional proof of her sense. She had undertaken the breaking of the news to the bereaved mother, and performed it to her own satisfaction. I believe she also broke it to the colonel and his bride when they returned from that indispensable excursion which people must take after the ceremony of white vails and orange blossoms, the half-score of bridemaids and elegant déjeuner. They do these things in style in South Carolina; and Miss Letitia had come through them so creditably, and had so much more to do in the way of receiving visits, and attending bridal-parties, that there was no time for regret or repentance. I never heard what she said or did on the occasion; but while the visits were going on, and the parties pending, poor Elva slipped on the stair while running up with a tucker, ordered in great haste, that Mrs. Col. Fosbrook might see how it would suit with her cream colored tabinet, fell to the bottom, and broke her leg. She had the best medical attendance, of course; a woman who could work such sleeves and collars was not to be neglected, though, as her excellent mistress remarked, "she could work just as well without the limb: what a mercy it was not one of her arms." But from some constitutional cause the accident could not be remedied—the broken bone would not adhere, the wound would not heal, and the doctor at length announced his dread of mortification. He added-I presume it was to settle Mrs. Fosbrook—that there was no use in attempting to amputate the limb, the patient's system had been so vitiated by her sedentary life she had no chance of recovery. His opinion was confirmed in a few days; mortification set in, and poor Elva's death-warrant was sealed. The doctor had been seeing her for the last time, and gone away saying he could do nothing more-the woman would not hold out till sunset, when I called to pay my congratulatory visit to the new-married pair. The ceremony had been post poned on account of business, but all the world was visiting, and so must I. It was a glorious day, in the early springtime of the South, before the fierce heat set in, and every thing looked bright and beautiful about Fosbrook Hall. The abode of pleasantness and peace it seemed, and I was admiring the prospect from the bay-windows of the drawing room; while Mrs. Fosbrook, having no other listeners, just then was going on about the overflowing cup, and how thankful they should be, when her own maid came in with a whispered message. "It is poor Elva," said the excellent lady, breaking off her strain; "she has taken a strange fancy to see us all in her room: the maid said she spoke of having something to tell; but of course it is only a fancy of the poor creature; still I think we should go-what do you say, Mr. Clarkson ?-it will remind us of our latter end, and no doubt encourage poor Elva.” We all rose, the two couples and myself, for Mr. Fosbrook said: "Come along, Clarkson," and proceeded to Elva's room. It was neat and orderly, as she had always kept it; the morning sun was shimmering through the white curtained window, and the scent of flowers came in from the garden beyond; and the woman, who was to be encouraged on her last journey, sat up in bed wan and worn with sickness, but looking more lively and energetic than ever she had seemed in her stitching-days, and with a keener light in her deep black eyes. "How are you, Elva?" said Fosbrook, coming kindly forward. "Not very well, master; but I am going home," said Elva, "to the long home prepared for black and white; and there is something I want to tell you all before I go, particularly the missis here;" and Elva fixed her eyes on the mistress she was said to have been so much attached to, with a look of such piercing power as for once in her life struck that lady speechless. "Did not you buy me away from my husband sixteen years ago, when he was sold far west, and I never saw him more? Did not you sell my only child away from me, till she died of fever on the edge of the Dismal Swamp, and wasn't it all in the order of Providence, or it never could have happened? You told me so, and I was to believe it, and not repine. Now, I'll tell you something that must have been in the order of Prov idence, for it happened too. It was not my daughter that died on the edge of the Dismal Swamp-but your own! It was not your daughter that went in the car riage and the finery to be married in Charleston church-but mine!" set aside as regarded poor sold Letty, and the fair face which had been such a cause of jealousy and despite. Moreover, the revelation could not be kept a secret-it was too publicly made; many of the servants had been within hearing, and nobody doubted it, though Elva could not be induced to give any further particulars. Perhaps the woman had none to give; at any rate, she spoke little after that wild laugh, but gradually sunk and died, as the doctor had predicted, an hour before sunset. Her tale made no apparent difference to the Fosbrook's; all things and all people remained in their places-there were the senior and the junior couples, the father and his son-in-law, the mother and her daughter; but it went abroad, was canvassed in every drawing-room and on every plantation, in Charleston clubs and coffee-houses, and wherever the Fosbrook's were known. It touched nothing "What do you say, woman?" cried Mr. Fosbrook, losing all command of himself. "I say the truth; and I'll tell you how it happened. The children were born on the same day; and the missis sent me word that they should get the same name, and be brought up together; but I knew that my child could be bought and sold as its father and mother had been. The poor slave was not used to be cared for, like the rich lady, and could get up sooner; so in the dead of the second night, when the monthly nurse had taken too much peach-brandy, and slept soundly, I crept into the room, and made a fair exchange-a black one may be you'll call it, but colors don't show at that time of life. I left my own child in the fine satin-cover-visible, yet their lives were changed, and ed cradle, and took Mrs. Fosbrook's baby to the basket beside my bed. The one was mine, and the other was hers ever after. There is my daughter, the heiress of Fosbrook Hall," she continued, addressing her mistress; "and yonder lies yours, in the churchyard by the Dismal Swamp. That is how the whites can make out blood and race; but it was all in the order of Providence, or it couldn't have happened, you know;" and Elva flung herself back with a burst of vengeful and triumphant laughter, that made the roof ring. "You wretch, it is all a falsehood! Where do you expect to go to ?" cried Mrs. Fosbrook. 'Madam, it is most probably true," said the colonel, who had stood silently listening at the foot of the bed, like a man heart-stricken and admonished-"it is most probably true. Let the dying woman alone: the past can neither be recalled nor altered; and she has followed our example, in calling our own sins and selfishness the works of Providence. Come away." We all walked back to the drawingroom, and the ladies did not faint. As for myself and every soul that heard Elva's confession, we felt convinced that it was true. Of course, in law, the testimony of a revengeful slave would count for nothing; but we had all eyes and memories, and their evidence was not to be the different effects were curious. Mr. Fosbrook's steady and domestic habits gradually forsook him; he took to the clubs, the gaming tables, it was said to all manner of dissipation, was never at home, and believed to be virtually separated from Mrs. Fosbrook. She continued to preach; I suppose nothing could alter the woman; but she was left very much in the background, for Fosbrook Hall became a lonely mansion, shorn of its splendor and retinue, between her husband's extravagance and a step to which the colonel urged him-namely, the gradual emancipation of all his negroes. The fact could be accomplished more easily at that time than in these days of ferment and civil war. It was managed by Mr. Fosbrook's son-in-law, on the estate which he had married for. How much he regretted the real heiress, and the misfortunes which had fallen upon her, for his sake, people could only conjecture; but certain it was, that from being gay and careless, he became a serious man, resigned his commission in the army, took to the emancipation business, but prudently and with forethought; and when it was fairly accomplished, and the negroes put in ways of getting their own living, he removed with his wife to Pennsylvania, where he entered the Society of Friends, and continued to the end of his days to be a moderate and rational abolitionist. He returned only once to South-Carolina, and that was at the time of Mr. Fosbrook's | wards, and got the reputation of being death, which happened ten years after the unlucky, for the populace, and especially colonel's marriage. Then he settled the old the negroes, gave the place a new title, lady in a first-rate boarding-house, and from some memory of Elva's confession, sold the Hall and plantation. I under- and called it the Black Exchange. stand it passed through many hands after From the Popular Science Review. COLOR - B L I NDNESS. BY JABEZ HOGG, F.L.S., ETC. THE eye-that index of the soul, that refrangibility, forming a series, and called channel of human knowledge-conjures up a host of feelings when the mind is directed to it as an object of especial attention. Of the five senses with which most of us have been blest, the loss of sight seems to be the greatest calamity that can befall us. Reflect for a moment on the condition of those deprived of this exquisite gift. To what a sad state are they reduced who, in a perpetual darkness in the midst of light, have not any thing like a conception of what we mean when we talk of the golden sun, the bright stars, the ever-varying tinted flowers, the beauty of spring, the glow of summer fields, the ripening fruits of autumn, and all beside that clothes the face of nature so beauteously to our eyes! Our theme, however, is not with those who have so large a claim to our sympathies, but rather with others among us who suffer from a partial kind of blindness - not necessarily a mechanical or optical defect, but one which is almost unknown or unrecognized by those who suffer from it, and, being ignorant of its existence themselves, can not easily be persuaded to believe it. An explanation of this curious defect will be worth while listening to, the more so as many eminent philosophers have suffered from it; and it is perhaps owing to this circumstance that so much time and attention has been given to the investigation of so curious an anomaly. It is well known that a ray of light, from any source, may be divided by means of a prism into a number of rays of different a spectrum, the most familiar instance of which is the rainbow. The drops of rain falling between the sun and the eye act as so many prisms, and each ray is thereby bent or refracted to a different angle, the red most and the blue least; and as thus the rays of light are made to enter the eye separately, we have produced the beautiful prismatic phenomenon of the rainbow, the outermost color of which is red, the innermost violet, and the intermediate, from slightly intermixing and overlapping each other, we respectively name orange, yellow, green, blue, and indigo. The three homogeneous colorsyellow, red, and blue-have been shown by Mr. Field, in a satisfactory manner, to be in the numerical proportional power as follows: yellow, three; red, five; and blue, eight. When these three colors are reflected from any opaque body in these proportions, white is produced; they are then said to be in an active state, but each is neutralized by the relative effect that the others have upon it. When they are absorbed, they are in a passive state, and black is the result. When transmitted through any transparent body, the effect is the same; but in the first case they are material or inherent, and in the second impalpable or transient. Color, therefore, depends entirely on the reflective or refractive power of bodies, as the transmission or reflection of sound does upon their vibratory powers. By the undulatory theory of light, philosophers account for the variously-colored rays of the solar spectrum, by calculating the differences in the frequency of the vi| brations of each ray-that is, the rays of light are supposed capable of vibrating in waves of different lengths. The shortest waves produce violet light, the longest red; and with such precision have some of the more complex phenomena of light been studied, that mathematicians have absolutely been able to calculate the number of vibrations necessary to produce an impression of either white or colored light. For instance, the periodical movements of the medium in white light regularly recur at equal intervals, five hundred millions of millions of times in a second of time; in the sensation of redness, our eyes are affected four hundred and eighty-two millions of millions of times; of yellowness, five hundred and forty-two millions of millions; of violet, seven hundred and seven millions of millions; and so on. How seldom do the most reflecting among us think, as we gaze on the flowers composing a bouquet, and inhale their fragrance which perfumes the surrounding air, that in order to distinguish the yellow tint of the laburnum, five hundred and forty-two millions of millions of undulations of light must occur; that the ruby fuschia requires the eyes to receive four hundred and eightytwo millions of millions of undulations in a second; that the violet's tint is only distinguishable when seven hundred and seven millions of millions of vibrations have penetrated to the sensitive retina! pure and absolute green, but only a resid- Assuming, therefore, that the sound eye can see perfectly well three simple colors-red, yellow, and blue--and that all the rest of the colors of the spectrum are mixtures of these with each other, let us now proceed to inquire what is the peculiar condition of sight in those persons who, being unable to distinguish certain rays, are, as we have already stated, colorblind; but not necessarily owing to disease of the optic nerve or retina, but simply arising from inability to recognize those rays of light which consist of pure red. When objects are illuminated by homogeneous yellow light, the only thing which can be distinguished by the eye is the difference of intensity or brightness. It is now a generally received opinion that different bodies, according to the manner in which their minutest particles are arranged, possess the power of variously absorbing a part and reflecting the other portion of the rays of light that fall upon them; and that on the proportions of the rays absorbed and reflected does the color depend, and that it is not a part of the object itself. The meaning of this will be best understood by an example. When a ray of light falls on the green Professor Maxwell, who has closely and grass, part of the ray is absorbed and part philosophically investigated the subject, reflected, and the grass is only seen with says: "The mathematical expression of the part that is reflected. The green we the difference between the color-blind and see consists of the original white light, ordinary vision is, that color to the fordeprived of a portion of its rays by absorp-mer is a function of two independent variation. It is, therefore, partial darkness, bles, but to an ordinary eye of three; and not absolute light, consequently not a and that the relation of the two kinds of vision is not arbitrary, but indicates the absence of determinate sensation, depending upon some undiscovered structure or organic arrangement, which forms one third of the apparatus by which we receive sensations of color. "Suppose the absent structure to be that which is brought most into play when red light falls on our eyes, then to the color-blind red light will be visible only so far as it affects the other two sensations, say of blue and green. It will, therefore, appear to them much less bright than to us, and will excite a sensation not distinguishable from that of a bluish-green light." That is to say, the normal eye reduces its color-sensations to three, and analyzes white light into three colored elements, one of which is red; and that the colorblind eye, on the other hand, reduces its color-sensation to two, and analyzes white light into two elements, neither of which is red; for color-blindness takes its character more from its non-recognition of red than its positive recognition of yellow and violet. An essential distinction which can thus be drawn between perfect vision and color-blindness has induced Sir J. Herschell to adopt the term dichromatic (cognizant only of two colors) to characterize the color-blind.* We shall now examine how far the withdrawal of the red ray affects other colors. In the first place, all the light tints, as well as the dark tints, are liable to be mistaken for each other. The orange is no longer red and yellow, but dark yellow; the yellow is purer, the green distinct, the blue purer, and the indigo and violet no longer red and blue, but blue mixed with more or less black, the violet being the darkest, as containing least blue in proportion to red, while the red part itself, though not seen as a color, is not perfectly black. The red is generally seen as gray, or neutral tint; the orange as a dingy yellow; the blue as a dirty indigo, and the violet as a pale blue, mixed with black and gray. well, to test the accuracy of his own eyes in distinguishing between shades of color; and his data may be followed by any one curious in the same field of inquiry. A large variety of all shades and tints of colored wools may be used for the purpose. They should be placed in a mixed heap before the person, who must try to arrange and name them, beginning with the darkest, and putting those tints together that are most alike. Professor Maxwell adds: "The intelligent testimony of the colorblind may supply a sure foundation for the theory of vision." Many other curious and interesting points in connection with the philosophical part of our inquiry might be entered upon did the space at command permit us to do so; but enough has been said about light and color to enable the reader to comprehend the more intricate part of the subject we are about to enter uponnamely, color-blindness. As I have already said, the defect does not necessarily interfere with the integrity of the eye as an optical instrument. Indeed, in a case recorded by Dr. Wilson of a Mr. Ran engraver, he counts himself not a sufferer, but a gainer by his color-blindness. Thus, an engraver has two negative colors to deal with-black and white. Now, when I look at a picture, I see it only in white and black, or light and shade; and any want of harmony in the coloring of a picture is immediately made manifest by a corresponding discord in the arrangement of the light and shade, or, as artists term it, the effect. I find, at times, many of my brother engravers in doubt how to translate certain colors of pictures which to me are matters of decided certainty and ease. Thus, to me it is valuable. I am totally unable to retain certain colors in my mind, nor able to give their names when shown to me a second time. Sometimes I can see some reds and greens by lamplight. A few years ago I ventured to buy some green baize, but unfortunately bought a very bright red, which was excessively painful to my eyes by lamplight, but agreeable enough by daylight. One of my brothers is equally defective, and my grandfather was very deficient in his knowledge of Dr. Wilson employs the term chromato-pseudop- colors. My sight is natural, and rather sis, (false vision of colors,) as it, he says, very powerful; for I am able to see very fairly expresses the general character of the affec-minute objects without assistance from tion, which more frequently shows itself as an insensibility to certain colors, than as a total glasses, and I can also see very distinctly inability to discern them." with but little light. With regard to In the Philosophical Magazine for 1857 and 1862 will be found a series of experiments, instituted by Professor Max VOL. LX-NO. 1 7 |