coloured thin plates of mica may sometimes be obtained by sticking a piece of mica and a piece of black sealing-wax together, and then tearing them suddenly asunder, when some very thin films will be left on the sealing-wax. Most persons must have observed, that pieces of glass, especially bottle-glass, when exposed for years to the action of the weather, become covered with beautiful colours. This is owing to the metals, lead, iron, and manganese, which are contained in the glass, becoming oxidized; and thus a very thin film of oxide (which when very thin is transparent,) is formed on the surface of the glass, to which it adheres so firmly that it cannot be scraped off, and thus becomes a thin plate, showing different colours according to its thinness. plane surface, he did not take a piece of common glass, for that is seldom perfectly plane; but he used the plane side of another telescope-lens, which had been ground as flat as art could make it. For the reader, however, who wishes to see, on a small scale, these phenomena, it will be enough to take a common spectacle or reading-glass, and lay it on a piece of common window-glass rubbed perfectly clean. He must not look through the two glasses; but hold them (either side upwards) in such a way as to see the sky reflected from them. If he then press them very tightly together, he will see, in the centre of the glass, a round black spot about as large as a peppercorn, and as he slightly varies the pressure of his fingers, it will appear to run about between the glasses. If he looks more closely at it, (or uses a small magnirings round the spot; but they will be too fine for him to distinguish any colours. These are called "Newton's rings," and with Newton's more perfect apparatus, they were some inches in diameter, and glowed with the brilliant hues of thin plates, arranged as in a soap-bubble, thinner at the centre than at the edges. The annexed figure (fig. 3,) shows the arrangement of these celebrated rings; A being the black spot, and the figures indicating the order of the rings. To this class also, are to be referred the colours formed in the same manner on various metals, espe-fying glass to look at it,) he will see six or seven small cially silver, when long exposed to air and damp; being likewise due to thin films of oxide, rust, or tarnish. Of this kind are the colours seen on steel during the process of tempering, which guide the experienced workman, who knows what particular tint corresponds with a particular degree of temper. The gradual increase of the heat thickens the film of oxide, and thus varies the colour. These colours are numerous and splendid; the blue colour of watch-springs is one of them. Fig. 3. Fluids can be made so thin as to exhibit colour, by many other modes besides that of blowing them into bubbles. Take a plate of glass, or a looking-glass, or what is still better, a piece of glass with the hinder surface painted black. Hold it so as to see the sky reflected from it, wet the upper surface, and gently wipe off the moisture, which will be reduced in many parts to such a thinness as to show bright colours, but not arranged in any particular order. Another mode of forming thin plates of fluid is to let fall a drop of an oily substance, as oil of turpentine, on the surface of water. Some substances, as balsam of Peru, instantly spread out into a layer so thin as to exhibit colour; but others, as oil of turpentine, spread out into a very thin film, but not thin enough to be- The reader will at once perceive the secondary come coloured. In this case, beautiful coloured rings cause of this phenomenon; for the law, which is the may be formed by holding just above, but not touch-primary cause of all these phenomena, we have not ing, the film, the tip of the finger dipped in sulphuric yet explained. The two glasses are in contact at the ether. The vapour of this very volatile substance recentre only, and even there the contact is not perfect; pels the film of oil, so as to produce a cup-shaped for modern science proves perfect contact to be imcavity just under the finger. The middle, or thinnest possible. The plate of air enclosed between the lenses part, is so thin as to be black; and around it are rings is, however, so very thin at the centre, as to appear of colours depending on the increasing thickness of like a black spot. But as one of the surfaces is conthe film. This experiment is due to Mr. Tomlinson, vex, it is separated from the other at the edge; and in whose Manual of Natural Philosophy, (Article, therefore at the edge, and for a'considerable distance SOAP-BUBBLE,) many other novel and striking expe- inwards, the plate of air is so thick, as to shew no riments connected with the colours of liquid films colour. Its thickness gradually diminishes as we may be found. approach the centre, until, at a certain point, colours begin and continue through various gradations of thinness, till we arrive at the excessively thin black spot. "The subjoined figure shews the arrangement adopted for observing the coloured rings, in which apparatus, two large object glasses are pressed Air and gases are easily reduced to thin coloured plates, by enclosing them between solid surfaces almost in contact. This was the method used by Newton, in forming a plate of air, to serve instead of a soap-bubble, in investigating the doctrine of thin plates. Fig. 2. Fig. 4. He took two surfaces of glass (fig. 2), one perfectly plane, and the other convex, with a radius of fifty feet, i.e., this latter surface had a curve so exceedingly small, that the sphere, if complete, would have been 100 feet in diameter. It was one of the surfaces of a large object-glass for a telescope, and its convexity was, of course, nearly imperceptible. For the other O together at their edges by three screws, by increasing the pressure of which, the size of the black spot is increased. more ON ALBINOS, OR WHITE NEGROES. AMONG the varieties of human beings, judging those varieties by external appearances, few are remarkable than the Albinos, or White Negroes. Albino is a word of Portuguese origin, signifying white negro, and was first applied to some natives of Central Africa, who were perfectly white, although the general form of their bodies was decidedly of a negro cast. Similar individuals, that is, similar so far as regards the pearly whiteness of the skin, have since been observed in various countries; but the same term, Albino, has been, and still is, applied to all of them. Before we speak of the causes of their peculiarities, we will cite a few instances of their existence, as given by different authors. Wafer, an old voyager, met with some Albinos in the Isthmus of Darien. He observes : Their skin is milk white, much like the colour of a white horse, and covered with a short down. They see not very well in the sun, poring in the clearest day; their eyes being but weak, and running with water if the sun shine towards them; so that in the day-time they care not to go abroad, unless it be a cloudy dark day. But notwithstanding their being thus sluggish and dull in the day-time, yet when moonshiny nights come, they are all life and activity, running abroad and into the woods, skipping about like wild bucks, and running as fast by moonlight, even in the gloom and shade of the wools, as the other Indians by day, being as nimble as they, though not so strong and lusty: hence they are called moon-eyed. Mr. Jefferson, in his Notes on Virginia, states that he had seen seven examples of this peculiarity in the negro race. Three of them were sisters, having two other sisters who were black. They were uncommonly shrewd and quick in apprehension and reply. Their eyes were in a perpetual tremulous vibration, very weak and much affected by the sun; but they could see better than other persons in the night. The fourth instance was a woman whose parents came from Guinea, and had three other children of their own colour. She was freckled, and had such weak eyes that she was obliged to wear a shade in the summer; but she saw better in the night. The last instance was a man, who was tall in stature, and had tremulous weak eyes. Dr. Winterbottom saw a white African woman, with a remarkably coarse and wrinkled skin: it was dry and harsh to the touch, and marked with deep furrows. It had a reddish tinge in parts exposed to the sun, being of a dirty white in other situations. Black spots, like freckles, the size of a pea, were thickly scattered over the skin. Another tall and well-formed white negro had a similar rough, harsh, and freckled skin. Another young white negress had the skin of an unpleasant dead-looking white, and pretty smooth, but beginning to assume a cracked appearance, from the action of the sun. Captain Cook describes five or six Albinos, which he saw at Otaheite. The skin was of a dead white, like the nose of a white horse, scurfy, and covered with a white down. They had white hair, beard, eyebrows, and eyelashes. Another example mentioned by Dr. Winterbottom, was the daughter of two mulattoes, born in Nova Scotia, who had all the negro features, with woolly hair of a dirty white colour, and a skin equalling in whiteness that of a European without anything disagreeable in its appearance or texture. Her eyes were between a red and a light hazel colour, and not much affected by light. Albinos are not confined to tropical nations. They have been met with among the natives of Germany, Denmark, England, Ireland, France, Switzerland Italy, the Grecian Archipelago, and Hungary These, then, being a few of the observations which various travellers have made respecting the existence of Albinos, we will proceed to state the views of anatomists and physiologists respecting the cause of this singular phenomenon. The general characteristics of the Albinos are― white skin, white hair, and reddish or pink eyes. The skin is generally of a pearly whiteness, without any admixture whatever of a pink or brown tint. In the snow-white skin of the fairest European female there is always a slight pinkish or brownish tint; but in the Albino the skin is generally wholly destitute of either, and is of a dull pearly whiteness. It has, however, not the soft and smooth texture of the skin of a European, but is very frequently harsh, rough, and dry. The hair, not only of the head, but also of the eyebrows, eyelashes, and beard, is white; but, as it has been observed, "this whiteness of the hair is not like the soft snowy whiteness of the hoary hair of old age, and still less like the delicate yellow or flaxen tint of the fair-haired European woman, but is rather like that of the white horse." mind the reader that when we speak of a person With regard to the colour of the eye, we must rehaving "hazel" or "blue" eyes, we allude to the colour of the iris, or that circular portion which surrounds the central hole, or pupil, of the eye. Now in the Albino this iris is generally of a pale rose colour, while the pupil itself has a disagreeable red tinge. Singular as it may appear that red eyes should accompany white skin and hair, physiologists are of opinion that one cause produces the whole; and to explain that cause, it will be necessary to consider the structure of the skin. The skin of the human body consists of three separate parts, the cuticle, or outer skin, the cutis, or inner skin, and a peculiar substance interposed between them. Now it is supposed that the cuticle has very little organic power in it: it is supposed to be almost wholly destitute of blood-vessels or nerves, and is in fact to act the part of a sheath to the delicate structures beneath it. The cutis, or inner skin, is, on the contrary, exquisitely sensible, and so profusely supplied with blood-vessels, that the smallest cut or prick will draw blood; and we must always remember that it is the cutting of the inner, and not of the outer skin, which occasions the flow of blood. Now both the inner and outer skin are perfectly colourless; but there is generally a substance interposed between them, which is coloured, and which imparts the particular tint to the body. In Negroes, Caffres, and Malays, this middle skin presents the form of a black or exceedingly dark membrane, about as thick as the cuticle, and is composed of a delicate cellular tissue, containing a dark substance, on which its colour depends. It is this dark substance which gives the black colour to the negro, since the actual skin itself is quite white and transparent. In other human beings this interposed substance is brown, red, yellow, or white, and thus affords all those varieties of tint which we observe in the inhabitants of different countries. This, then, being the case, we shall be prepared to believe that if the central skin, or cellular membrane, in an Albino, contain a substance perfectly white, or if the middle skin be absent altogether, either supposition will account for the pearly whiteness which they present. Such is the opinion arrived at some anatomists doubt whether the central skin exists at all in a white person, but all are agreed, that if it exist, it is perfectly free from colour. Precisely the same line of reasoning will apply in the case of the hair. It is believed that the colour of the hair, in human beings generally, is due to a coloured substance, contained in an inner cellular membrane, and that the whiteness of an Albino's hair results from the absence of that substance. With respect to the eye, the same mode of reasoning, slightly modified, will apply. The interior of the hinder half of the eye is covered with a black substance, called pigmentum nigrum, or black paint, the object of which is supposed to be to absorb, or stifle in some way, the rays of light, after they have performed their office in the production of vision. The hinder surface of the iris is also coated in a similar manner, probably to prevent rays of light from gaining access to the interior of the eye by any other channel than the pupil. This black coating is observed in the eyes of nearly all human beings, but it is absent in the Albino, and the visible redness is due to bloodvessels. The important office which the eye has to perform requires the aid of an exceedingly numerous assemblage of blood-vessels, both in the hinder part of the interior of the eye, and in the iris. These vessels are, in ordinary cases, concealed by the black substance of which we have spoken; but in the Albino, the black being absent, the light soon irritates these vessels, and they become filled with red blood, which gives to the part where they are situated the appearance of a red, more or less intense. A great deal of discussion has occurred among medical men, as to whether the peculiarities of the Albino are the result of disease, or whether they are to be ranked merely as similar instances to the varieties of colour among cattle, horses, &c., which, whatever may be their cause, do not appear to be the result of disease. We cannot pursue this subject farther, but it appears to be the general opinion that Albinos are not subject to any particular disease; but that the inability which they manifest to bear strong light, and one or two other circumstances peculiar to them, are natural results of the absence of that colouring matter to which we have alluded, but do not indicate anything that may be called disease. It has been remarked that a great many other animals besides man present occasionally specimens similar to the Albino, in regard to white skin and hair, and red eyes. Among the animals enumerated aresheep, pig, horse, cow, dog, cat, rabbit, mouse, ferret, monkey, squirrel, rat, hamster, guinea-pig, mole, opossum, martin, weasel, roe, fox, rhinoceros, elephant, badger, beaver, bear, camel, buffalo, ass, crow, blackbird, canary-bird, partridge, common fowl and peacock. THE true art of being agreeable, is to appear well pleased with all the company, and rather to seem well entertained with them than to bring entertainment to them. A man thus disposed, perhaps, may have not much learning, nor any wit; but if he has common sense, and something friendly in his behaviour, it conciliates men's minds more than the brightest parts without this disposition; and when a man of such a turn comes to old age, he is sure to be treated with respect. It is true, indeed, that we should not dissemble and flatter in company; but a man may be very agreeable, strictly consistent with truth and sincerity, by a prudent silence where he cannot concur, and a pleasing assent where he can. Now and then you meet with a person so exactly formed to please, that he will gain upon every one that hears or beholds him; this disposition is not merely the gift of nature, but frequently the effect of much knowledge of the world, and a command over the passions.The Spectator. HABIT hath so vast a prevalence over the human mind that there is scarce anything too strange or too strong to be asserted of it. The story of the miser, who from long accustoming to cheat others, came at last to cheat himself, and with great delight and triumph picked his own pocket of a guinea to convey to his hoard, is not impossible or improbable.-FIELDING. THE DOLPHIN. MOST persons are familiar with the form of this fish, as represented in heraldry, and on fishmongers' signs, than which, however, nothing can be more ridiculously incorrect. from a drawing taken from nature; but the superlaThe true form is here represented tive beauties, and magical transitions of colours, which the fish exhibits when dying, and for which it describe. Indeed the sudden and frequent alternations is so remarkable, no pen or pencil could adequately and elaborate combinations of effect, so completely defeat the efforts of the pencil, that the pen has the advantage in the attempt; and the following descripfaithful record we have seen in writing:— tion from FALCONER'S Shipwreck, is perhaps the most But while his heart the fatal javelin thrills, To persons who have never witnessed the painfully interesting sight of the dying dolphin, the above description may be thought to partake too much of the fabulous stories which have been related of this fish. Even an intelligent writer, of recent date, and one who had crossed the Atlantic, speaking of the manchineel tree, whose deleterious properties have been somewhat exaggerated, observes, that "the common stories about the fatal shade of this tree, are as fabulous as the changing colours of the dying dolphin." There are many persons, however, who have been eye-witnesses of the fact; and the writer of this paper now refers to an instance which came under his own observation. This The fish, which was a large one, and was taken with a line, evinced extraordinary power, while in the water, but on reaching the deck, it became passive, indicating a stiffness that seemed to deny it the power of much action, beyond raising its tail occasionally, and flapping it on the deck with great force. inertness was probably occasioned by exhaustion from the length of time (about twenty minutes) it had been struggling at the end of the line, before it could be brought to the ship's side. Some idea may be formed of the velocity with which this fish travels through the water, when we state that the vessel was going at the rate of eight miles in the hour, and that the first intimation given of a fish being hooked to the line, which was of considerable length, and had been towing astern, was from its being carried, with a prodigious strain on it, abeam, or abreast of the ship, and during the time the fish was "in play," it was frequently before the beam. The fin that runs from the top or back part of the head to the tail, is of a dark blue-black; a dark blue pervades the upper part of the back, but it is susceptible of a partial change to a green, particularly in a glare of light. As it approaches the sides, it gradually takes a lighter shade, till it softens into a rich cerulean blue, commingled with delicate hues of golden pink; these again, by similar gradations, fall into a bright yellow or amber, at the belly; the post-branchia and under-fins, being of the same colour, but much darker; and the whole surface of the sides is beauti fully bespangled with vivid light blue spots. These several colours frequently relaxed into subdued tones, and again returned to their former complexion and brightness, presenting in the progress, the most fantastic involution of hues, till, at length, the whole body assumed a cold silvery blue and purple cast, varying in its shades, but deepest about the back, where a rich bloom continued to play on the surface. As the period of dissolution approached, and during its last paroxysms, the same transitions occurred in quicker succession, though infinitely less vivid on each occasion, till in expiring the body became violently convulsed; and as the trembling gradually subsided, a dull silvery slate colour crept, as it were, over the whole surface; and, settling in the stiffness of death, presented an aspect so intensely cold and ghastly that it produced a shivering thrill in the spectators. It is to be observed that this fish is most frequently taken with the harpoon, when death is materially accelerated; and most commonly when it is caught with a line, the sailors kill it, before, or immediately after, it is brought on deck; whence it is obvious that these singular manifestations are only partially portrayed. This fish seldom exceeds four feet in length, and is commonly not more than two or three feet. It is without scales, and has a firm and smooth skin. Its flesh is rather coarse and dry, but the sailors regard it as a bonne bouche, after a too familiar acquaintance with salt provisions. It is proper to state one circumstance which has no doubt encouraged a disbelief in the natural peculiarities of this fish; namely the existence of another fish which among modern naturalists bears the name of the Dolphin, (Delphinus), and which belongs to the cetaceous tribe, having a close resemblance to the porpoise. The fish we are more particularly noticing is the Cocyphaena hippuris, of the order of Thoracici, of Linnaeus, the Dorado of the Portuguese, and is un | questionably the Dolphin of the ancients, if we may judge, not only from the ordinary representations of it, but from those representations being in accordance with the figure on the coin of Alexander the Great, preserved by Belon, and which gives it the declined and truncated head, and the back fin running the whole length from the head to the tail; whereas the Delphinus has no such fin, and its head tapers towards the mouth, terminating with what may be termed a snout. We have further evidence in the term "the arrow of the sea," from its remarkable swiftness, especially when in pursuit of its prey, THE FLYING FISH. As these diminutive inhabitants of the ocean rise from the watery element, their silvery brightness, and the delicacy of their forms, beautifully contrasting with the dark blue waters beneath them, and rendered more vivid and sparkling when the sun's rays or the pale moon-beams catch their glistening wings, they produce an effect of singular beauty, and one which seems to partake of the influence of enchantment. But to the reflective mind there is something painfully interesting in going from the effect to the cause, and there to find the truth exemplified, that there is much that is beautiful to the sight, that is allied to misery and suffering. To escape from their pursuers they leave their native element to avoid destruction; but the penetrating vision of the dolphin, when aided by the unobscured light of a tropical sun upon the waters, marks their shadows on the surface, and he follows their course till their wings become dry and relaxed, when they drop with the noise of a hail-stone shower, and become an easy prey: those that escape again rise with replenished powers, again and again, as necessity dictates; thus passing a transitory and precarious existence, alternately inhabitants of the air and of the water. Nor is this the scope of their vicissitudes; for in their attempt to elude their enemies of the deep they frequently become a prey to the aquatic birds, which scize them on the wing. LONDON: Published by JOHN WILLIAM PARKER, WEST STRAND and sold by all Booksellers. |