and is received in a cylindrical box L, in the centre of which a fluted cylinder revolves, which gives the fleeces a spiral form, the first element of the thread. The next operation is performed by the slubbingbilly. It reduces the cardings by drawing them out in lengths, joins them in a continuous spongy cord, giving them at the same time a slight twist to prevent their breaking. The wool is now in the state of a soft thread, similar to a roving in the cotton manufacture, and is called a slubbing; it is now ready to be spun into a thread of a harder texture. The operation of slubbing and spinning in worsted so nearly agree with the same processes in the cotton manufacture, that it would be unnecessary again to enter upon the subject. When the cloth first comes from the weaver, it is in a very rough unsightly state, and contains a quantity of oil, with which it has become combined during the several processes it has undergone. The next operation is scouring, which is performed in the fulling-mill, the cloth being soaked in an alkaline ley, and beaten by machinery; it is then well rinced with pure water and hung on the tenter-frames to dry. When dry, it is taken down and examined carefully, the knots picked out, and any rents or cuts it may have received, repaired by introducing fresh threads; this is called burling. The cloth has now to be thoroughly cleaned in the fulling-mill, by means of soap and water The next process is milling, or felting. In the state in which the cloth is received from the tenter-field, the naked threads are very perceptible, and the operation of milling is to swell the threads, and felt them so as to allow of the cloth afterwards receiving that fine smooth and polished surface, which is the great beauty of fine cloth, and which renders it also more impervious to wet. Commonly, a piece of cloth of sixty-two yards, requires six pounds of soap, which is dissolved in water, and about a handful spread upon each yard in length; the piece is then put into a trough and worked for three hours in the fullingmill. After twelve hours milling, the cloth is reduced in breadth about two-fifths, and in length one-third; it is now again strained on the tenter-frame, by which it is stretched about one-twentieth, or two yards in forty, but it is very little extended in breadth. The property of felting is only possessed by the short wool, and it is of so singular a nature, that it deserves particular notice. If an ear of bearded corn is introduced between the wristband and the wrist, the stalk being placed towards the shoulder, the common motions of the arm will cause the ear of corn to move upwards until it reaches the shoulder, and this occurs whether the arm is thrust out of the sleeve or drawn back; this motion takes place by means of the jagged ends of the grains of corn. The thrusting of the arm outwards would naturally tend to thrust forwards the ear, but the sharp angles of the grain fixing themselves firmly into the shirt-sleeve, maintain the ear in its situation; if the arm is drawn in, the same cause enables the ear to catch hold of the skin and to be drawn upwards, and this is repeated every time the arm is drawn inwards or forced outwards. Now the construction of the hair of the sheep and the ear of corn is somewhat similar, and the magnified view of three kinds of wool, fig. 3, will show the reason why one sort will felt and the other will not. The long English wool A, it will be seen, is much less notched on its surface than the Saxon B, or the original Spanish c, and therefore resembles less the ear of corn, and will not be acted on in the same manner. The fibres of the cloth made of short wool on being subjected to the operation of fulling, shrink considerably in their length, and close in, as it were, upon each other. The jagged ends of this wool now become entangled, and any attempt to stretch the cloth again to its original length and width would be useless; the more frequently this operation of fulling is repeated, the thicker the texture of the cloth becomes, and it is then said to be double milled. We know that if common woollen cloth, when made up into a garment, should get wet, it shrinks considerably, much to the annoyance of the wearer, who, in this manner, has it milled upon his own person. The felting of wool in the manufacture of hat bodies, is effected by acting on the same principles, but the process is more frequently repeated, so as to cause the fibres of the wool to be completely matted together. After the milled cloth has been properly dried, it has to be dressed; this was formerly done by means of the seed-vessels of the fuller's teasle, formed into a kind of hand card, but latterly it has been effected by machinery, and in some cases by means of very fine wire cards. The dressing is the process by which the nap is raised. The last operation the cloth has to undergo is called shearing, or cropping; the wool, by the operation of dressing, covers the surface of the cloth like loose fur, which must be removed before it is fit for the market; this was formerly effected by hand with a large pair of shears, but of late years this part of the manufacture has also been performed by the aid of machinery. The cutting instruments resemble the blades of the hand shears, one blade is fixed in an oblique direction, while a revolving cylinder is furnished with several moving blades, which act in succession against the fixed blade, in the same manner as if a pair of shears were worked by hand. The cloth itself is stretched over a metal bed to prevent its lying in creases. The list being thicker than the rest of the fabric is left unsheared, the blades of the | stramonium, and bella donna. The well-known effect cutters not being of a sufficient width to cut the nap which these substances possess of dilating the pupil with which it is covered, and as the list is thicker when applied to the surface of the eye, or of the than any other parts of the cloth, grooves are con- neighbouring parts, differs only in degree from what trived for its reception, and to allow the shears to follows their being taken into the stomach; but clip close. instead of effecting a loss of power or paralysis of the iris, they seem rather to act as stimuli on the antagonist fibres which compose the greater ring of the iris, and thus overcome its normal or regular obedience to the stimulus of light, analogous to those involuntary and spasmodic actions which they occasion when taken internally. See VETCH on Diseases of the Eye, CHRISTISON also in his Treatise on Poisons, cites numerous interesting cases of the effect of narcotic poisons on the pupil of the eye, Some of the common woollen cloths are hotpressed to give them a face, and as this smoothness should only appear on one side, the other is made rough again by means of a sponge and water; this kind of cloth is also dyed after weaving, and the list is sewn on to give it the appearance of having been dyed ingrain. ON EMPLOYMENTS WHICH INJURE THE EFFECTS OF THE EXPOSURE OF THE EYE (4.) We need not offer more than one illustration to this class, inasmuch as others will be readily suggested to the reader's own mind when we state that many fumes, vapours, gases, such as those afforded by ammonia, muriatic acid, &c., so affect the sentient apparatus of the eye as to cause a general irritability which the eye itself tends to remove by exciting a flow of tears. This power, however, is lost in time: inflammation comes as a prelude to disease of a permanent and more lasting character. The case we have selected is a remarkable one, illustrating the noxious effects resulting from exposure of the person to acrid fumes. A class of persons employed in cleansing the immense sewers of the city of Paris are subject to a disease which is called in one case la mitte, in the other case le plomb. The former is caused by ammoniacal vapours, and is announced by a smarting in the eyes, and the eye-ball and pupil soon become red, accompanied with other pains, chiefly about the head. Blindness often results, which lasts for a day or two. The patients endure much pain, and get no relief until tears begin to flow. In slight attacks exposure to the open air and shading the eyes is a sufficient remedy: if the attack is strong the men are accustomed to wash their eyes in cold water, to tie a wet bandage over them, and to remain in the dark. Le plomb is also due to gaseous exhalations, chiefly sulphuretted hydrogen and ammoniacal gases, producing convulsions and other alarming symptoms. The danger to these workmen is now entirely removed by the copious use of chlorine in combination with lime or soda, as chlorine possesses the valuable property of entirely destroying and neutralizing these effluviæ. It is perhaps in this place that we may mention a train of effects resulting from narcotics taken inwardly. The effects produced do not certainly come under the denomination of fumes as ordinarily considered; but, be that as it may, the subject is one of much importance, and we do not wish to pass it over unnoticed. Amaurosis is caused by the use of narcotic substances which have been supposed to act specifically in depressing the energy of the nervous system in general. The symptoms of amaurosis, however, by no means support the opinion that they have a direct sedative operation: the loss of sensibility, as well as the dilatation of the pupil, may be the effect of increased excitement, or a full state of the vessels; for besides considerable external turgescence, sensibility of the pupil almost invariably returns on having recourse to bleeding. The principal substances of this class are opium in large doses, hyosciamus, LAVA. MOUNT VESUVIUS. IT was in the month of February (1793) that I went with a party to the source of the lava, for the first time, to ascertain the real state in which the lava proceeded from the volcano that created it. I found the crater in a very active state, throwing out vollies of immense stones, transparent with vitrification, and such showers of ashes involved in thick sulphurous clouds, as rendered any approach to it extremely dangerous. We ascended as near as possible, and then, crossing over to the lava, attempted to coast it up to its source. This we soon found was impossible, for an unfortunate wind blew all the smoke of the lava hot upon us, attended at the same time with such a thick mist of minute ashes from the crater, and such fumes of sulphur, that we were in danger of being suffocated. In this perplexity I proposed immediately crossing the current of liquid lava, to gain the windward side of it, but felt some fears, owing to the very liquid appearance the lava there had so near its source. All my companions were against the scheme, and while we stood deliberating, immense fragments of stone and huge volcanic bombs, that had been cast out by the crater, but which the smoke had prevented us from observing, fell thick about us, and rolled by us with a velocity that would have crushed any of us, had we been in their way. I found we must either leave our present spot, or expect instant death therefore, covering my face with my hat, I rushed upon the lava, and crossed over safely to the other side, having my boots only a little burnt, and my hands scorched. Not one of my companions, however, would stir; nor could any persuasion of mine avail in getting a single guide over to me. I then saw clearly the whole of the scene, and expected my friends would every moment be sacrificed to their own imprudence and want of courage, as the stones from the crater fell continually around them, and vast rocks of lava bounded by them with great force. At last I had the satisfaction of seeing them retire, leaving me entirely alone. I begged hard for a torch to be thrown over to me, that I might not be lost when the night should come on. It was then that André, one of the cicerones of Resina, afer being promised a bribe, ran over to me, and brought with him a bottle of wine and a torch. We had coasted the lava ascending for some time, when looking back I perceived my companions endeavoring to cross the lava lower down, where the stream was narrower, In doing this they found themselves insulated, as it were, and surrounded by two different rivers of liquid fire. They immediately pressed forward, being terribly scorched by the combined heat of both the currents, and ran to the side where I was; in doing which one of the guides fell into the middle of the red-hot lava, but met with no other injury than having his hands and face burnt, and losing at the same time a bottle of vin de grave, which was broken by the fall, and which proved a very unpleasant loss to us, being ready to faint with excessive thirst, fatigue, and heat. Having once more rallied my forces, I proceeded on, and in about half an hour I gained the chasm through which the lava had opened itself a passage out of the mountain. To describe this sight is utterly beyond all human ability. My companions shared in the astonishment it produced; and the sensations they felt, in concert with me, were such as can be obliterated only with our lives. All I had before seen of volcanic phenomena did not lead me to expect such a spectacle as I then beheld. I had seen the vast rivers of lava that descended into the plains below, and carried ruin and devastation with them; but they resembled a vast heap of cinders, or the scoria of an iron-foundry, rolling slowly along, and falling with a rattling noise over one another. Here a vast arched chasm presented itself in the side of the mountain, from which rushed, with the velocity of a flood, the clear vivid torrent of lava in perfect fusion, and totally unconnected with any other matter that was not in a state of complete solution, unattended by any scoriæ upon its surface, or gross materials of an insolvent nature, but flowing with the translucency of honey, in regular channels, cut finer than art can imitate, and glowing with all the splendour of the sun. of materials less soluble than the rest of the lava, lighter, and of course liable to float continually on the surface. There is, however, no truth in this. All lava at its first exit from its native volcano flows out in a liquid state, and all equally in fusion. The appearance of the scoria is to be attributed only to the action of the external air, and not to any difference in the materials that compose it, since any lava whatever, separated from its channel, at its very source, and exposed to the action of the external air, immediately cracks, becomes porous, and alters its form. As we proceeded downwards this became more and more evident, and the same lava which at its original source flowed in perfect solution, undivided, and free from loose encumbrances of any kind, a little farther down had its surface loaded with scoria, in such a manner, that upon its arrival at the bottom of the mountain, the whole current resembled nothing so much as a rolling heap of unconnected cinders from an iron-foundry. During my second visit the appearances were pretty much the same. I though the lava flowed slower, and was less in fusion than before, the surface appearing tougher, and being sooner converted into scoria. We dressed our beef-steak upon the lava, no fire being better calculated for that purpose, owing to the excessive heat it gives. Upon my third visit I found the lava had taken a different course, and flowed towards the Torre del Annonciato, whereas it had before procceded in a channel exactly opposite the cross. The source itself had undergone great alterations, and bore strongly the marks of an earthquake.--BISHOP OTTER'S Life of Clarke. The fury of the crater continuing to increase, menaced us with destruction if we remained any longer in its neighbourhood. A large stone, thrown out to a prodigious height, hung for some time over our heads in the air. Every one gave himself up for lost, until it fell harmless beyond us, shattering itself into a thousand fragments, which rolled into the valley below. We had not left this spot above five minutes before a shower of stones, issuing from the crater, fell thick upon it, covering the source of the lava, The eruption from the crater increased with so and all the parts about it; so that had we waited, much violence that we proceeded to make our expe- as I begged to do, a little longer, every one of us riments and observations as speedily as possible. A would have been crushed to atoms. little above the source of the lava I found a chimney of about four feet in height, from which proceeded smoke, and sometimes stones. I approached and gathered some pure sulphur, which had formed itself upon the edges of the mouth of this chimney, the smell of which was so powerful, that I was forced to hold my breath all the while I remained there. I seized an opportunity to gain a momentary view down this aperture, and perceived nothing but the glare of the red-hot lava that passed beneath it. We then returned to examine the lava at its source. Sir W. Hamilton had conceived that no stones thrown upon a current of lava would make any impression. We were soon convinced of the contrary. Light bodies of five, ten, and fifteen pounds' weight made little or no impression, even at the source; but bodies of sixty, seventy, and eighty pounds, were seen to form a kind of bed upon the surface of the lava, and float away with it. A stone of three hundred weight, that had been thrown out by the crater, and laid near the source of the current of lava, I raised upon one end, and then let it fall upon the liquid lava, when it gradually sunk beneath the surface, and disappeared. If I wished to describe the manner in which it acted upon the lava, it was like a loaf of bread thrown into a bowl of very thick honey, which gradually involves itself in the heavy liquid that surrounds it, and then slowly sinks to the bottom. The lava itself had a glutinous appearance; and although it resisted the most violent impression, seemed as if it might easily be stirred with a common walking-stick. A small distance from its source, as it flows on, it acquires a darker tint upon its surface, is less easily acted upon, and, as the stream gets wider, the surface having lost its state of perfect solution, grows harder and harder, and cracks into innumerable fragments of very porous matter, to which they give the name of scoria, and the appearance of which has led many to suppose that it proceeded thus from the mountain itself, being composed THERE is inconsistency and something of the child's propensities still in mankind. A piece of mechanism, as a watch, a barometer, or a dial, will fix his attention. A man will make journeys to see an engine stamp a coin or turn a block; yet the organs through which he has a thousand sources of enjoyment, and which are in themselves more exquisite in design, and more curious both in contrivance and in mechanism, do not enter his thoughts; and if he admire a living action, that admiration will probably be more excited by what is uncommon and monstrous, than by what is natural and perfectly adjusted to its office, by the elephant's trunk than by the human hand. This does not arise from an unwillingness to contemplate the superiority or dignity of our own nature, nor from an incapacity of admiring the adaptation of parts. It is the effect of habit. The human hand is so beautifully formed, it has so fine a sensibility, that sensibility governs its motions so correctly, every effort of the will is answered so instantly, as if the hand itself were the seat of that will. Its actions are so powerful, so free, and yet so delicate, that it seems to possess a quality of instinct in itself, and there is no thought of its complexity as an instrument, or of the relations which make it subservient to the mind: we use it as we draw our breath, unconsciously, and have lost all recollection of the feeble and ill-directed efforts of its first exer cise by which it has been perfected. Is it not then the very perfection of the instrument which makes us insen sible to its use?-BELL. THE CICADA, AND ITS ORGANS OF VOICE. THE Cicada are insects belonging to the order called Hemiptera, (half-winged,) on account of the wings partaking generally of a double character, being partly of a leathery substance and partly transparent; in the Cicadæ, however, this distinction is not so apparent. The Cicada are found in abundance in most of the warmer parts of the globe; there are also several species, natives of more temperate regions. These insects are noted for the singular noise they produce, and on this account they were in great favour among the ancient Greeks. They were kept in cages for the sake of their song, and were a favourite image of innocence and cheerfulness with the poets of Greece. One bard intreats the shep herds to spare the innoxious Tettix, (the Greek name for the Cicada,) that nightingale of the Nymphs, and to make those mischievous birds, the thrush and blackbird, their prey. Sweet prophet of the Summer, (says Anacreon, addressing this insect,) the Muses love thee; Phoebus himself loves thee, and has given thee a shrill song; old age does not wear thee out; thou art wise, earthborn, musical, impassive, without blood. The sound produced by the Grecian Cicada must necessarily have been musical; it was called by the same name as the music of the harp. A Cicada, sitting upon a harp, was a usual emblem of the science of music, which was thus accounted for:-When two rival musicians, Eunomus and Ariston, were contending upon that instrument, a Cicada, flying to the former, and sitting on his harp, supplied the place of a broken string, and so secured him the victory. The Cicada of modern times are equally famous for the power, if not for the musical property of their voice. Dr. Shaw, in his Travels, says, In the hotter months of Summer, especially from midday to the middle of the afternoon, the Cicada is perpetually stunning our ears with its most excessively shrill and ungrateful noise. It is, in this respect, the most troublesome and impertinent of insects, perching upon a twig, and squalling sometimes two or three hours without ceasing, thereby too often disturbing the studies or short repose, which is frequently indulged in in these hot climates for a few hours. The Brazilian Cicada are said to sing so loud, that they can be heard at the distance of a mile. On account of the sound this insect produces, it is called in the United States, the American Locust. The apparatus by which the male Cicada produces the sound for which it is famous, is thus described in Kirby and Spence's beautiful work on Entomology. If you look at the underside of the body of a male, the A Fig. 1. first thing that will strike you is a pair of large plates, of an irregular form, B; in some semioval, in others triangular, in others again a segment of a circle of greater or less diameter, covering the anterior part of the belly; these are the drum-covers, or opercula, from beneath which the sound issues, at the back of the posterior legs. Just above each operculum there is a small pointed triangular process, (persillum,) A, the object of which, as Réaumur supposes, is to prevent them from being too much elevated. When an operculum is removed, beneath it you will find, on the exterior side, a hollow cavity, with a mouth somewhat linear, (like a slit, the width of a line,) fig. 2, A, which seems to open into the interior of the abdomen. Next to this, on the inner side, is another large cavity, B, of an irregular shape, the bottom of which is divided into three portions: of these the posterior is lined obliquely with a beautiful membrane, which is very tense, c; in some species semi-opaque, and Under View, with the Drumcovers in their Places. B A in others transparent, and reflects all the colours of the rainbow; sound, but is supposed to modulate this mirror is not the real organ of it. The middle portion is occupied by a plate, of a horny substance, placed horizontally, and forming On the bottom of the cavity B. its inner side this plate terminates in a crania, or elevated ridge, common to both drums. Between the cplate and the after-breach, (post pectus,) another membrane, folded transversely, fills an oblique, oblong, or semilunar cavity. În some species I have seen this membrane stretch or relax it at pleasure, but in tension, probably the insect can Fig. 2. Under View, with the Dra covers turned back. even all this apparatus is insufficient to produce the sound of these animals. One, still more important and curious, still remains still to be described. This organ can only be discovered by dissection. A portion of the first and second segments being removed from that side of the back of the abdomen which answers to the drums, two bundles of muscles, fig. 3, B, meeting each other in an acute angle, attached to a place opposite to the point of the mucro (a pointed prominence, like a sharp tooth,) of the first ventral segment of the abdomen will appear. These bundles consist of a prodigious number of muscular fibres, applied to each other, but easily separable. Whilst Réaumur was examining one of these, pulling it from its place with a pin, he let it go again, and immediately, though the animal had been long dead, the usual sound was emitted. their sounds, here are parts enough to do it for them, for the mirrors, the membranes, and the central portions with their the cavities, all assist in it. If you remove the lateral part of the first dorsal segment of the abdomen, you will discover Fig. 3. If these creatures are unable themselves to modulate a semi-opaque, and nearly semicircular concave-convex membrane, with transverse folds, fig. 3, A; this is the drum. Each bundle of muscles before mentioned, is terminated by a tendinous plate, nearly circular, from which issue several little tendons that, forming a thread, pass through an aperture in the horny piece that support the drum, and are attached to its under or concave surface. Thus the bundle of muscles, being alternately and briskly relaxed and contracted, will by its play, draw in and let out the drum, so that its convex surface being thus rendered concave when pulled in, when let out, a sound will be produced by the effort to recover its convexity, which sound striking upon the mirror and the other membrane. before it escapes from under the operculum, will be modulated and augmented by them. I should imagine that the muscular fibres are extended and contracted by the alternate approach and recession of the trunk and the abdomen to and from each other. Back View; several Portions of the Skin removed to show the Drum GENERAL FEATURES OF THE WORLD ACCORDING TO THE GEOGRAPHERS JUST BEFORE THE CHRISTIAN ERA. PART II. CAUSES OF THE ROMANCE OF ANCIENT NAVAL HISTORY. WE have already observed that the scene of the earliest known navigation was the Mediterranean Sea, which naturally seemed to the ancients to be situated in the middle of the earth; as is implied by its name. As navi gation advanced only at a creeping pace, and as but a small amount of fresh experience was laid up by one generation for the benefit of the next, it took very many ages to explore the Mediterranean, Tyrrhene, Hadriatic, and Egean seas. The people of Tyre and Sidon, the Phoenicians, "whose merchants were princes," (Isaiah xxiii. 8,) were among the first whom the spirit of commerce and the desire of gain had made dissatisfied with what had hitherto VOL. XII. seemed the natural limits of marine excursion. The great antiquity of the Phoenicians, however, is perhaps the reason why our knowledge of them is obtained from incidental and isolated accounts: but on the naval spirit and industry of Carthage, a colony planted by the former power, in the ninth century before Christ, the light of history, owing to their connexion with the Romans, is more abundantly shed. With the Carthaginians, perhaps, had originated the idea of quitting the Mediterranean by the straits of Gades, (now Gibraltar,) of sailing southward, circumnavigating the coast of Africa, and then returning northward by the Red Sea, towards the Levant, or eastern side of the Mediterranean. This notion seems to have been cherished for ages, as the prime, the crowning enterprise, long thought of and debated; but which only a solitary few, at long intervals of time determined to try 379 |