is an art much more generally practised than understood. It supposes, says Chaptal, 1st, a knowledge of the different substances capable of staining any kind of cloth; 2d, of the substances to which recourse must be had, in order to make those deposited on the stuff to disappear; 3d, a knowledge of the effects produced on colours by those reagents, which it may be necessary to employ to destroy stains; 4th, a knowledge of the manner in which the cloth is affected by those re-agents; 5th, of the art of restoring a colour changed or faded. Of those bodies which occasion spots on different kinds of cloth, some are easily distinguished by their appearance, such as greasy substances; but others have more complex effects, such as acids, alkalies, perfumed matter, fruits, urine, &c. Acids reddish black, fawn, violet, and puce-colour, and every shade communicated with orchilla-weed, iron, astringents, and every blue except indigo and prussian blue. They render the yellow paler, except that of annatto, which they change into orange.
Alkalies change to violet the reds produced by Brazilwood, logwood, and cochineal. They render the greens on woollen cloth yellowish, make yellow brownish, and change the yellow produced by annatto to aurora. Perfumed matter produces the same effects as alkalies.
When the spots are produced by simple bodies on stuffs, it is easy to remove them by the means already known. Greasy substances are removed by alkalies, soaps, the yolk of eggs, fat earths; oxyds of iron, by the nitric and oxalic acids; acids by alkalies, and reciprocally. Stains of fruit on white stuffs may be removed by the sulphurous acid, and still better by the oxygenated muriatic acid. But when the spots are of a complex kind, it will be necessary to employ several means in succession. Thus, to destroy the stain of coom from carriage-wheels, after the grease has been diffused, the oxyd of iron may be removed by the oxalic acid.
As colours are often changed by re-agents, it will be necessary, in order to restore them, that the scowrer should possess a thorough knowledge of the art of dyeing, and how to modify the means according to circumstances. This becomes the more difficult, when it is necessary to reproduce a colour similar to that of the rest of the stuff, to apply that colour only in one place, and often to restore the mordant by which it was fixed, and which has been destroyed, or even the first tint which gave the colour its intensity. It may be readily conceived, that the means to be employed must depend on the nature of the colour and the ingredients by which it was produced; for it is known that the same colour may be obtained from very different bodies. Thus, after an alkali has been employed to destroy an acid spot on browns, violets, blues, poppies, &c., the yellow spot which remains may be made to disappear by a solution of tin; a solution of fulphat of iron restores the colour to brown stuffs which have been galled; acids restore to their former splendour yellows which have been rendered dusky or brown by alkalies; blacks produced by logwood become red by acids; alkalies change the red spots to yellow, and a little of the astringent principle makes them again become black. A solution of one part of indigo in four parts of sulphuric acid, diluted with a sufficient quantity of water, may be employed with success to revive the blue colour of cotton or wool which has been changed. Scarlet may be revived by means of cochineal and a solution of the muriat of tin, &c.
The choice of re-agents is not a matter of indifference. Vegetable acids are preferable; the sulphurous acid, however, may be employed for stains occasioned by fruit; it does not change the blue of silk nor colours produced by astringents; it does not degrade the yellow of cotton. Ammonia succeeds better than fixed alkalies in removing spots produced by acids. It is employed in vapour; its action is speedy, and seldom alters the colour.
The means of removing greasy spots are well known. This effect is produced by alkalies, fullers earth, volatile oils diffused in alcohol, a heat proper for volatilizing grease, &c. Spots occasioned by ink, rust, or iron-mould of any kind, and all those produced by the yellow oxyd of iron, are removed by the oxalic acid: the colour may be restored by alkalies, or a solution of the muriat of tin. These spots may be removed also by the oxygenated muriatic acid, when they are on white stuffs or paper.
The action of alkalies, and that of perfumed matter, are the same: their spots may be effaced by acids, or even by a weak solution of the muriat of tin. When these spots arise from several unknown causes, in order to destroy them, recourse must be had to polychrest compositions. The following may be considered as one of the most efficacious: Dissolve white soap in alcohol, and mix this solution with the yolks of from four to five eggs; add gradually essence of turpentine; and incorporate with the whole some fullers earth, in such a manner as to form balls of a suitable consistence. Moisten the spot; and having rubbed it with these balls, the spot will be removed by washing the stuff. All spots, except iron mould and ink, may be removed in this manner.
Washing destroys the lustre, and leaves a tarnished place disagreeable to the eye; but the lustre may be restored by drawing over the washed place, and in the direction of the pile, a brush moistened in water, impregnated with a little gum. You may then apply a sheet of paper, or a piece of cloth, and a considerable weight, under which the cloth must be left to dry.
SYLLA. Under this title we gave, in the Encyclopaedia, an account of Scylla and Charybdis, which, though taken from a work which we thought good authority, appears to be far from correct. These places, so famous in the poems of Homer and Virgil, were examined with minute attention by that accurate observer of nature the Abbé Spallanzani; who thus describes Scylla.
"It is a lofty rock, distant twelve miles from Messina, which rises almost perpendicularly from the sea on the shore of Calabria, and beyond which is the small city of the same name. Though there was scarcely any wind, I began to hear, two miles before I came to the rock," rock, a murmur and noise like a confused barking of dogs, and on a nearer approach readily discovered the cause. This rock, in its lower parts, contains a number of caverns, one of the largest of which is called by the people there Dragona. The waves, when in the least agitated, rushing into these caverns, break, dash, throw up frothy bubbles, and thus occasion these various and multiplied sounds. I then perceived with how much truth and resemblance of nature Homer and Virgil, in their personifications of Scylla, had portrayed this scene, by describing the monster they drew as lurking in the darkness of a vast cavern, surrounded by ravenous barking mastiffs, together with wolves, to increase the horror.
Such is the situation and appearance of Scylla; let us now consider the danger it occasions to mariners. Though the tide is almost imperceptible in the open parts of the Mediterranean, it is very strong in the strait of Messina, in consequence of the narrowness of the channel, and is regulated, as in other places, by the periodical elevations and depressions of the water. Where the flow or current is accompanied by a wind blowing the same way, vessels have nothing to fear, since they either do not enter the strait, both the wind and the stream opposing them, but cast anchor at the entrance; or, if both are favourable, enter on full sail, and pass through with such rapidity that they seem to fly over the water. But when the current runs from south to north, and the north wind blows hard at the same time, the ship which expected easily to pass the strait with the wind in its stern, on its entering the channel is retarded by the opposite current, and, impelled by two forces in contrary directions, is at length dashed on the rock of Scylla, or driven on the neighbouring sands; unless the pilot shall apply for the succour necessary for his preservation. For, to give assistance in case of such accidents, 24 of the strongest, boldest, and most experienced sailors, well acquainted with the place, are stationed night and day along the shore of Messina; who, at the report of guns fired as signals of distress from any vessel, hasted to its assistance, and tow it with one of their light boats. The current, where it is strongest, does not extend over the whole strait, but winds through intricate meanders, with the course of which these men are perfectly acquainted, and are thus able to guide the ship in such a manner as to avoid it. Should the pilot, however, confiding in his own skill, contemn or neglect this assistance, however great his ability or experience, he would run the most imminent risk of being shipwrecked. In this agitation and conflict of the waters, forced one way by the current, and driven in a contrary direction by the wind, it is useless to throw the line to discover the depth of the bottom, the violence of the current frequently carrying the lead almost on the surface of the water. The strongest cables, though some feet in circumference, break like small cords. Should two or three anchors be thrown out, the bottom is so rocky that they either take no hold; or, if they should, are soon loosed by the violence of the waves. Every expedient afforded by the art of navigation, though it might succeed in saving a ship in other parts of the Mediterranean, or even the tremendous ocean, is useless here. The only means of avoiding being dashed against the rocks, or driven upon the sands in the midst of this furious contest of the winds and waves, is to have recourse to the skill and courage of these Messinese seamen."
Charybdis is situated within the strait, in that part of the sea which lies between a projection of land named Punta Secca, and another projection on which stands the tower called Lanterna, or the light-house, a light being placed at its top to guide vessels which may enter the harbour by night. Every writer, who has hitherto described Charybdis, has supposed it to be a whirlpool; but this is a mistake, as Spallanzani has completely proved, by ascertaining what it really is.
"Charybdis is distant from the shore of Messina about 750 feet, and is called by the people of the country Calofaro, not from the agitation of the waves, as some have supposed, but from ουσιας and ουσιας; that is, the beautiful tower, from the light-house erected near it for the guidance of vessels. The phenomenon of the Calofaro is observable when the current is descending; for when the current sets in from the north, the pilots call it the descending rema, or current; and when it runs from the south, the ascending rema. The current ascends or descends at the rising or setting of the moon, and continues for six hours. In the interval between each ascent or descent, there is a calm which lasts at least a quarter of an hour, but not longer than an hour. Afterwards, at the rising or setting of the moon, the current enters from the north, making various angles of incidence with the shore, and at length reaches the Calofaro. This delay sometimes continues two hours; sometimes it immediately falls into the Calofaro; and then experience has taught that it is a certain token of bad weather."
When our author observed Charybdis from the shore, it appeared like a group of tumultuous waters; which group, as he approached, became more extensive and more agitated. He was carried to the edge, where he stopped some time to make the requisite observations; and was then convinced, beyond the shadow of a doubt, that what he saw was by no means a vortex or whirlpool.
Hydrologists teach us, that by a whirlpool in a running water we are to understand that circular course which it takes in certain circumstances; and that this course or revolution generates in the middle a hollow inverted cone, of a greater or less depth, the internal sides of which have a spiral motion. But Spallanzani perceived nothing of this kind in the Calofaro. Its revolving motion was circumscribed to a circle of at most 100 feet in diameter; within which limits there was no incursion of any kind, nor vertiginous motion, but an incessant undulation of agitated waters, which rose, fell, beat, and dashed on each other. Yet these irregular motions were so far placid, that nothing was to be feared in passing over the spot, which he did; though their little bark rocked very much from the continual agitation, so that they were obliged constantly to make use of their oars to prevent its being driven out of the Calofaro. Our author threw substances of different kinds into the stream. Such as were specifically heavier than the water sunk, and appeared no more; those which were lighter remained on the surface, but were soon driven out of the revolving circle by the agitation of the water.
Though from these observations he was convinced that there was no gulph under the Calofaro, as other- wife there would have been a whirlpool, which would have carried down into it the floating substances; he determined to found the bottom with the plummet, and found its greatest depth did not exceed 500 feet. He was likewise informed, to his no small surprize, that beyond the Calofaro, towards the middle of the strait, the depth was double.
When the current and the wind are contrary to each other, and both in their greatest violence, especially when the seiloceo, or south wind, blows, the swelling and dashing of the waves within the Calofaro is much stronger, more impetuous, and more extensive. It then contains three or four small whirlpools, or even more, according to the greatness of its extent and violence. If at this time small vessels are driven into the Calofaro by the current or the wind, they are seen to whirl round, rock, and plunge, but are never drawn down into the vortex. They only sink when filled with water, by the waves beating over them. When vessels of a larger size are forced into it, whatever wind they have they cannot extricate themselves; their sails are useless; and after having been for some time tossed about by the waves, if they are not assisted by the pilots of the country, who know how to bring them out of the course of the current, they are furiously driven upon the neighbouring shore of the Lanterna, where they are wrecked, and the greater part of their crews perish in the waves.
From these facts, the classical reader will perceive, that the ancient descriptions of Charybdis are by no means so accurate as those of Scylla. The saying, however, which became proverbial among the ancients, viz. that "he who endeavours to avoid Charybdis, dashes upon Scylla," is, in a great measure, true. If a ship be extricated from the fury of Charybdis, and carried by a strong northerly wind along the strait towards the northern entrance, it will indeed pass out safely; but should it meet with a wind in a nearly opposite direction, it would become the sport of both these winds, and, unable to advance or recede, be driven in a middle course between their two directions, that is to say, full upon the rock of Scylla, if it be not immediately assisted by the pilots. It is likewise observed, that in these hurricanes a land wind frequently rises, which defends from a narrow pass in Calabria, and increases the force with which the ship is impelled towards the rock.
SEA-SICKNESS is a disorder which has been but little treated of, notwithstanding the frequency of its occurrence, and the irksomeness and distress to which the patient is subjected during its continuance. It has been found to be very beneficial in several diseases, among which the principal are asthmatic and pulmonary complaints; and there are very few instances of its being attended with fatal consequences. The sea-sickness seems to be a spasmodic affection of the stomach, produced by the alternate pressure and recess of the contents of that viscus against its lower internal surface, according to the rise and fall of the ship opposes or recedes from the action of gravity.
The seas in which this disorder attacks the passenger with the greatest violence, are those where the waves have long uninterrupted freedom of action; of course, bays, gulfs, and channels, may be navigated with less inconvenience, as the waves, meeting with more frequent resistance, and the repercussion being considerably stronger, the vessel does not experience that gentle uniform form oscillation which tickles the stomach, and renders the head giddy. By the same argument, a person feels less inconvenience from the disorder on the wide ocean in a small vessel, on which the slightest motion of the waves makes a strong impression. He is likewise less exposed to it in a very large vessel, as in a ship of the line, or a large merchantman deeply laden; as the waves, in this case, scarcely affect the vessel. It is in ships of the middling size, and which carry but a light cargo, that the passenger suffers most from the sea sickness. It has been observed, that this disorder affects people in years less than young persons; those of a dark less than those of a fair complection, and that it seldom attacks infants. The duration is not limited to any fixed period of time; with some it lasts only a few days, with others weeks, months, and even during the whole course of the voyage. The sooner it takes place after embarkation, the greater probability is there of its continuance. It does not always cease immediately on landing, but has been known, in some cases, to continue for a considerable time. Even the oldest and most skilful seamen have experienced a relapse, especially if they have quitted the sea service for a long term of years.
There have been many modes recommended for mitigating, if not entirely preventing, this disorder; among which the following seem the most efficacious:
1. Not to go on board immediately after eating; and, when on board, not to eat in any great quantity at any one meal.
2. To take strong exercise, with as little intermission as conveniently can be done; for instance, to assist at the pumps, or any other active employment, as indolent and slothful passengers always suffer most from the disorder.
3. To keep much upon deck, even in stormy and rainy weather, as the sea breeze is less liable to affect the stomach than the stagnated air of the cabin, which is frequently rendered infectious for want of sufficient circulation.
4. Not to watch the motion of the waves, especially when strongly agitated with tempest.
5. To avoid carefully all employments which harass the mind, as reading, study, meditation, and gaming; and, on the other hand, to seek every opportunity of mirth and mental relaxation.
6. To drink occasionally carbonic acids, as the froth of strong fermented beer, or wine mixed with Seltzer water, and fermented with pounded sugar, or a glass of Champagne.
7. It will be found of great service to take the acid of sulphur dulcified, dropped upon lump sugar, or in peppermint-water; or ten drops of sulphurous ether.
With regard to eating, it is advisable to be very sparing, at least not to eat much at one meal. The proper diet is bread and fresh meat, which should be eaten cold with pepper. All sweet flavoured food should be carefully avoided; and the passenger should refrain from fat, but especially from all meat that is in the least degree tainted. Even the odour of flowers is very pernicious; for which reason, it is not expedient to examine marine productions, as these generally have a nauseating smell. The fumes of vinegar may be inhaled with great benefit. The drink should consist of tart tart wines, lemonade, or Seltzer water, but never of common water. The passenger would do well to drink little and often. An experience has proved, that an accidental diarrhoea has frequently relieved the patient from the sea-sickness; it will be prudent to follow the clue of nature, and take a gentle laxative, or, if circumstances will permit, a clyster of salt-water and Venice soap, which is the more necessary, as sea-faring people are liable to obstructions. It will further be found useful to apply to the pit of the stomach a tonic anodyne antispasmodic emplastrum, spread upon leather, and covered with linen.
Where the above preventives have not been employed, or have not succeeded in securing the passenger from the sea-sickness, he may, however, experience considerable relief from the following remedies:
If symptoms of vomiting appear, they may frequently be remedied by the patient prostrating himself in a horizontal position, upon the back or belly, and lying perfectly still. We would recommend likewise a gentle compression of the abdomen. But if the fits of vomiting are too violent to be repressed, in that case, it is best to promote them by a strong dose of salt-water; an expedient, however, which must not be too often repeated, as it tends still more to weaken the stomach. When the emetic takes effect, let the patient bend his body, advancing his knees towards his breast, and support his head against a firm and solid resting-place. He must be particularly careful to untie his garters and cravat, as this precaution will secure him from the risk of a rupture, and from the ill effects of the blood rushing violently towards the head and breast.
After the vomiting has subsided, its return may be guarded against by preserving a state of repose, and even keeping the eyes shut for a considerable time. Let the patient choose a cool, ventilated place, remembering to keep himself warm and well clothed, as perspiration is highly salutary. But he must not indulge in too long sleep during the daytime, as this induces torpidness. In the morning he should constantly take a gargle of sugar dissolved in vinegar. Let him eat often, but sparingly; and if he can content himself with a dish of chocolate, coffee, or strong tea, he will reap still greater benefit. He should never drink water in its pure elementary state, but mix it with brandy, vinegar, or wine. In the morning, instead of brandy, he may take a glass of wine, with an infusion of orange peel, gentian root, or peruvian bark (quinquina). A glass of punch taken occasionally will prove of very essential service, as it promotes perspiration.
Persons in the habit of smoking, will find a pleasant and salutary companion in the pipe; but those who are not accustomed to it will be sufferers by taking to the practice.
In conclusion, it is proper to add, that warm clothing, flannel shirts, trowsers, caps, &c. are efficacious remedies against excessive expectoration, and all other symptoms of this terrible disorder.
SECTOR OF A SPHERE, is the solid generated by the revolution of the sector of a circle about one of its radii; the other radius describing the surface of a cone, and the circular arc a circular portion of the surface of the sphere of the same radius. So that the spherical sector consists of a right cone, and of a segment of the sphere having the same common base with the cone.
And hence the solid content of it will be found by multiplying the base or spherical surface by the radius of the sphere, and taking a third part of the product.