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through the holes into the water, and SHROWDS, or SurouDS, in a ship, are form itself into shot ; do thus till all your the great ropes which come down both lead is run through the holes of the plate, sides of the masts, and are fastened below taking care, by keeping your coals alive, to the chains on the ship's side, and abaft that the lead does not cool, and so stop to the top of the mast; being parcelled up the holes.

and served, in order to prevent the mast's While you are casting in this manner, galling them. The top-mast-shrowds are another person with another ladle may fastened to the puttock plates, by dead catch some of the shot, placing the ladle eyes and lanyards, as the others are. Some four or five inches underneath the plate of the terms relating to the shrouds are ; in the water, by which means you will ease the shrouds, that is, slacken them; see if they are defective, and rectify and set up the shrouds, that is, set them them. Your chief care is to keep the lead stiffer. in a just degree of heat, that it shall not SHUTTLE, in the manufactures, an be so cold as to stop up the holes in your instrument much used by weavers, in the plate, nor so hot as to cause the shot to middle of which is an eye or cavity, crack; to remedy the heat, you must re. wherein is inclosed the spool with the frain working till it is of a proper cool. woof. See WEAVING. ness; and to remedy the coolness of your

SIBBALDIA, in botany, so named in lead and plate, you must blow your fire;

memory of Sir Robert Sibbald, professor observing, that the cooler your lead is,

of physic at Edinburgh, a genus of the the larger will be your shot; as, the hot

Pentandria Pentagynia class and order. ter it is, the smaller they will be.

Natural order of Senticosæ. Rosaceæ, After you have done casting, take them

Jussieu. Essential character: calyx tenout of the water, and dry them over the

cleft; petals five, inserted into the calyx; fire with a gentle heat; stirring them

styles from the sides of the germ ; seeds continually, that they do not melt; when

five. dry, you are to separate the great shot

There are three species. from the small, by the help of a sieve SIBTHORPIA, in botany, so named in made for that purpose, according to their honour of Humphrey Sibthorp, M. D. several sizes. But those who would have professor of botany at Oxford, a genus of very large shot, make the lead trickle the Didynamia Angiospermia class and with a stick out of the ladle into the wa. order. Natural order of Pediculares, ter, without the plate. If it stops on the Jussieu. Essential character: calyx fiveplate, and yet the plate is not too cool, parted; corolla five-parted, equal : stagive the plate but a little knock, and it mina in remote pairs; capsule compresswill run again ; care must be had that ed, orbicular; two-celled, with the partinone of your implements are greasy, oily, tion transverse. There is only one species, or the like; and when the shot, being viz. S. Europæa, Cornish money-wort, a separated, are found too large or too 'native of Portugal and England, in shady small for your purpose, or otherwise im. places; it flowers in July and August. perfect, they will serve again at the next SICE ace, a game with dice and tables, operation.

whereat five may play; each having six Suor, patent milled, are thus made ; men, and the last out losing. At this sheets of lead, whose thickness corres. game, they load one another with aces; ponds with the size of the shot required, sixes bear away; and doublets drinks, are cut into small pieces, or cubes, of the and throws again. form of a die. A great quantity of these SICYOS, in botany, a genus of the Molittle cubes are put into a large hollow noecia Syngenesia class and order. N&iron cylinder, which is mounted horizon. tural order of Cucurbitaceæ. Essential tally, and turned by a winch ; when, by character: calyx five-toothed ; corolla their friction against one another, and five-parted; male, filaments three; fe. against the sides of the cylinder, they are male, style trifid; drupe one-seeded. rendered perfectly round and very There are three species. smooth. The other patent-shot are castSIDA, in botany, a genus of the Moin moulds, in the same way as bullets nadelphia Polyandria class and order. are.

Natural order of Columniferæ. MalvaSHRIMP, in ichthyology, the English ceæ, Jussieu. Generic character: calyx name of two different species of the perianth, one-leafed, angular; corolla, squilla, viz. the common shrimp, and the petals five, wider above, emarginate, fassmooth-nosed shrimp. See Squilla. tened below to the tube of the stamens;

VOL. XI.

stamina, filaments very many, united be. set out at the beginning; and the stary low into a tube, in the apex of the twoth, will be advanced 50% of a degree with re. divided : pericarpium, capsule roundish, spect to that point. Consequently, if the angular, composed of five or more cells; sun's centre be on the meridian with any seeds solitary There are ninety.nine star on any given day of the year, that star species, natives of warm climates; and will be 14' 19' 45'+ 510" or 15' 9'' 45'' most of them are found in the East or east of the sun's centre, on the 365th day West Indies. The Chinese make cords afterward, when the sun's centre is on of the S. abutilon. This plant loves wa. the meridian; and therefore that star will ter, and may be advantageously planted not come to the meridian on that day till in marshes and ditches, where nothing the sun's centre has passed it by 1'0"38"" else will grow. The maceration of the 57"'' of mean solar time; for the sun takes smaller stalks is finished in about fifteen so much time to go through an arc of 15' days; of the larger in a month. The 91' 45''; and then, in 365d jb l' 0' 38"" strength and goodness of the thread ap- 57''", the star will have just completed its pears to be in proportion to the perfec. 366 h revolution to the meridian. . tion of the vegetation, and to the distance SIDERITE, a name given by Bergman that the plant is kept at from other plants. to a supposed peculiar metallic substance, The fibres lie in strata, of which there which is the principal cause of the brit. are sometimes six; they are not quite tleness of some kinds of bar iron. This straight, but preserve an undulating di. has long since been discovered as the rection, so as to form a net-work in their phosphate of iron. natural positions. Their smell resembles SIDERITIS, in botany, iron-wort, a gethat of hemp; the fibres are whiter, but nus of the Didynamia Gymnospermia more dry and harsh than those of hemp. class and order. Natural order of VertiThe harshness is owing to a greenish glu. cillatæ. Labiatæ, Jussieu. Essential chaten which connects the fibres ; and the racter: calyx five-cleft; corolla ringent; white colour must always be obtained at upper lip bifid, lower three-parted; stathe expense of having this kind of thread mina within the tube of the corolla ; stigless supple; when of its natural hue, it is ma, the shorter involving the other. very soft and flexible.

There are twenty species. SIDE. The half of any thing, as an ani. SIDEROXYLON, in botany, iron-wood, mal, a ship, &c. The sides of an aniinal a genus of the Pentandria Monogynia are distinguished into the right and left class and order. Natural order of Duside : but those of a ship, into the star. mosæ. Sapotæ, Jussieu. Essential chaboard and larboard side. In geometry, racter: corolla five-cleft; nectary fivethe sides of a rectilinear figure are the leaved; stigma simple; berry five-seed. lines which form its periphery.

ed. There are nine species, chiefly naSides men, or Synou's men, persons tives of the Cape of Good Hope. who, in large parishes, are appointed to: SIEGE, in the art of war, the enassist the churchwardens, in their inquiry campnient of an army before a fortified and presentments of such offenders to the place, with a design to take it. The ordinary, as are punishable in the spiric method of encamping is very different tual court.

in a siege from that observed on a SIDEREAL day, is the time in which march ; as in the former the army envi. any star appears to revolve from the me. rons the place without cannon-shot, that ridian to the meridian again; which is nothing may enter. If the place be si. 23 hours 56' 4" 6"" of mean solar time ; tuated on a river, a detachment is sent there being 366 sidereal days in a year, to the other side, and bridges of comor in the time of 365 diurnal revolutions munication made, both above and below of the sun; that is, exactly, if the equi. the town. The army also encamp with noctial points were at rest in the heavens. their backs to the town, with the batBut the equinoctial points go backward, talions and squadrons interlined ; and with respect to the stars, at the rate of having taken possession of all the 50" of a degree in a Julian year; which heights, whence the enemy may be an. causes the stars to have an apparent pro. noyed, the engineers trace the lines of gressive motion eastward 50% in that time. circumvallation and contravallation ; eveAnd as the sun's mean motion in the ry regiment working at the place apecliptic is only 11 signs 29° 45' 40" 15" pointed them. See FORTIFCATION. Cap. in 365 days. it follows, that at the end of tain James, in his Military Dictionary, that time he will be 14' 19" 45" short of has given the following rules, which that point of the ecliptic from which he ought to be adopted in sieges. The approaches should be made without being mortars for throwing stones, 12; shells seen from the town, either directly, ob. for mortars, 15 or 16,000 ; hand greliquely, or in the fank. No more works nades, 40,000 ; leaden bullets, 180,000; should be made than are necessary for matches in braces, 10,000; Aints for approaching the place without being muskets, best sort, 100,000; platforms seen; i. e. the besiegers should carry on complete for guns, 100; platforms for their approaches the shortest way possi. mortars, 60; spare carriages for guns, 60; ble, consistent with being covered against spare mortar beds, 60: spare sponges, the enemy's fire. All the parts of the rammers, and ladles, in sets, 20; tools to trenches should mutually support each work in trenches, 40,000. other; and those which are furthest ad.. Several hand-jacks, gins, sling-carts, vanced, should be distant from those travelling forges, and other engines prothat defend them above 120 or 130 per to raise and carry heavy burdens ; toises, that is, within musket-shot. The spare timber, and all sorts of miners' parallels, or places of arms the most tools, mantles, stuffed gabions, fascines, distant from the town, should have a pickets, and gabions greater extent than those which areS [ENITE, in mineralogy, one of the the nearest, that the besiegers may be compound primitive rocks that consists able to take the enemy in Aank, should essentially of crystals and grains of hornhe resolve to attack the nearest parallels. blende imbedded in felspar. Quartz and The trench should be opened or begun mica are occasionally found in sienite, but As near as possible to the place, without in very small quantity. It is commonly exposing the troops too much, in order in mass, and is rarely either schistose or to accelerate and diminish the operations stratified. It sometimes contains metallic of the siege. Care should be taken to veins join the attacks; that is, they should SIEVE, or SEARCE, an instrument serv. have communications, to the end that ing to separate the fine from the course they may be able to support each other. parts of powders, liquors, and the like; Never to advance a work, unless it be or to cleanse pulse from dust, light grains, well supported; and for this reason, in &c. It is made of a rim of wood, the cir. the interval between the second and cle or space whereof is filled with a plexthird place of arms, the besiegers should us of silk, tiffiny, hair, linen, wire, or make, on both sides of the trenches, even thin slices of wood. The sieves smaller places of arms, extending 40 or which have large holes, are sometimes al. 50 toises in length, parallel to the others, so called riddles, such as the coal or lime and constructed in the same manner, sieve, the garden sieve, &c. When drugs which will serve to lodge the soldiers in, are apt to evaporate, on being passed who are to protect the works designed through the sieve, it is usual to bave it to reach the third place of arms. Take covered with a lid care to place the batteries of cannon in SIGESBECKIA, in botany, so named the continuation of the faces of the parts from John Georg- Siegesbeck, a German, attacked, in order to silence their fire; prefect of the Petersburg garden, a geand to the end that the approaches, be. nus of be Syngene sia Polygamia Supering protected, may advance with great Aua class and order. Nailiral order of safety and expedition. For this reason Compositæ Oppositifoliæ. Corymbiferæ, the besiegers should always embrace the Jussieu. Essential character: calyx es. whole front attacked, in order to have as terior, five-leaved, proper, spreading; much space as is requisite to place the ray balved; pappus none; receptacle batteries on the produced faces of the chaffy. There are three species. works attacked. Do not begin the at. SIGHT, sense of. The organ of sight tack with works that lie close to one is a globular body, which contains within another, or with rentrant angles, which it transparent substances, fitted to form would expose the attack to the cross fire on the back part of it a picture of the ob. of the enemy.

ject of sight. An examination of the eye “ Stores required for a month's siege of an ox will give a pretty accurate idea are as follow :" powder, as the garrison of the general structure of the human is more or less strong, 8 or 900,000lb.; eye. We see in front a borny transpashot for battering pieces, 6,000; shot rent substance, called the cornea. Next of a lesser sort, 20,000; ballering can to this is a watery Auid, called the aquenon, 80 ; cannons of a lesser sort, 40; ous humour, in which the iris floats like small field.pieces for defending the lines, a delicate curtain, with a hole in the nud. 20; mortars for throwing shells, 24 ; die, called the pupil. Behind the iris we find a solid body with two convex sur. cle of plain glass, of not more than half faces; this is called the crystalline lens. an inch iri diameter, you may see through Next to this is the vitreous humour, a that circle the most extensive prospects, jelly like, transparent substance, which lawns, and woods, and arms of the sea, and fills the ball of the eye. The retina con- distant mountains. You are apt to ima. sists of exceedingly minute fibres from gine that the visible picture, which you the optic perve, wbich are spread over thus see, is immensely great and extenthe whole of the back part of the inner sive; but it can be no greater than the surface of the eye. Behind the retina is visible circle through which you see it. a mucous or slimy matter, which in the If, while you are looking through the cirhuman eye is of a dark colour, and serves cle, you could conceive a fairy hand and to imbibe the rays of light which pass a fairy pencil to come between your eye through the retina, so as to prevent the and the glass, that pencil might delineate confusion which would arise from the re. upon that little glass the outline of all Hection of them. The retina is the imme. those extensive lawns, and woods, and diate organ of sight. The rays of light, arms of the sea, and distant mountains, in proceeding froni every visible point of the dimensions with which they are seen The object of sight, enter the eye through by the eye.” Again, it is obvious, that the cornea, and pass through the pupil; however large, or however small, the they are refracted by the three humours field of view, the picture occupies an of the eye, so as to form upon the retina equal extent on the retina. Similar ob. an exquisitely beautiful and distinct, servations may be made with respect to though ininute, picture of the object. A distance. The organ of sight can conpretty correct idea of the formation of vey only that sensation of distance which this picture may be obtained, by care may be produced by a minute picture on fully cutting off the back coating of an the retina; that is, nothing but the sensaox's eye, and holding behind it a piece of tion of the distances of the different parts paper to receive the picture of a lumi. of the picture, which may bear no pronous object. For a more minute occount portion to the real distances, and can onof the structure of the eye, see Ana- ly be in one direction. Similar things TOMY.

may be said of motion, that is, change of What effect is produced upon the op. position. The visible sensation of motion tic nerve by the formation of this picture is merely that prociuced by the motion upon the retina is not certainly known; it of different parts of the picture on the is sufficieni for our present purpose, that, retina. by means of the nerve, &c. the impression, The fact is, that not the objects themwhatever it be, is communicated to the selves, but the picture formed upon the mental organs, and produces in them retina, is the immediate object of the those effects, which, when attended with sight. Without the sense of touch, it is consciousness, are called sensations. See probable that the picture would never MENTAL PuiLOSOPHY, S 11.

have conveyed ideas of real figure, magIf the sensation produced by the object nitude, motion, or position ; still more, of sight be considered, unblended with that it would never have conveyed the the relics of other sensations, we find that idea that external objects produced the it is merely what can be communicated picture. Of colour it does convey sensaby a minute picture on the retina. The tions, which do not receive correction sensation of colour can be thus communi. from the touch, and which can be ac. cated, and this is the only sensation which quired by the sight alone. Persons com. can be considered as appropriate to the pletely blind have been known to distin. sight. The sensation of figure can be guish objects of one colour from those of thus communicated, but only of figure in another, but this is by the feel of the surtwo directions, length and breadth : for faces of those objects. If they have never the picture on the retina can have only at all possessed sight, though they may those two dimensions. The sensation of speak of colours, and distinguish culoured magnitude.can also be thus communicat. objects, and even have a remote idea of ed, but not of real magnitude ; for the vi. the causes of our sensations of colours, sible sensation of real magnitude cannot yet, they can have no sensations, por be conveyed by a picture, which is al. consequently ideas of colours. Mr. Locke most indefinitely smaller than the real mentions a blind man, who said, that he object. To use the illustration of Adam imagined the colour of scarlet resembled Smithı: “If you shut one eye, and hold the sound of a trumpet. immediately before the other a small cir. The limits here stated of the direct power of the sense of sight may appear signs of the ideas derived from the touch ; strange to those who have not been ac. and from their distinctness well calculat. customed to distinguish between the sen. ed to serve as the connecting bond of sation, and the perception of wrich the union, and to bring again into the view of sensation forms a part. (See SENSATION ) the mind those ideas. The visual sensa. We seem to have an immediate sensation tions, of themselves considered, are sel. of the real situation and magnitudes, &c. dom the objects of reflection : we seldoin of objects; but what has been before stat. even think of them, and while we appear ed is an indisputable fact. The case is, to give to the visible appearances of obthe compound idea, formed from the sen). jects our minutest attention, we are in sations of touch, in connection with cer- part attending only to the tangible qualitain visual sensations, are so early form- ties of which the visible appearance is ed, and so early connected with those vi- the sign. Were it not therefore for as. sual sensations, that we have no recollec- sociation, the sight would be of little tion of the simple idea of sensation, or of more use to us than a beautiful picture of the formation of the compound idea ; in. objects with which we have no concern. deed, as active agents, we had no concern But consider its value in connection with in the formation of our perceptions. association, and it must be regarded as There are, however, numerous circum the most perfect and the most permastances which prove the point ; the nently valuable of all the senses. The most satisfactory are those attending the information obtained by the touch is acobtaining of the sight, at a period when quired slowly; and the sensations must recollection can register the sensations. be continually repeated, in order to acOne such case fell under the observation quire information respecting new ob. of the able Cheselden, and we shall state jects; but the sight takes in a vast varie, some of the principal circumstances of it. ty of objects, and, almost at a glance, can Mr. C. couched a youth of thirteen years distinguish most that is necessary to be of age; when he was allowed to use his known respecting them. Its sensations sighi, all objects appeared to him alike to recall the past impressions derived from touch his eyes, as the things which in the touch, and at once suggest the size, felt touched his skin. He considered so. the shape, the distance of their various lid bodies as planes differently coloured; objects. “If a man,” says Reid, “were and when he had learned to distinguish by feeling to find out the figure of the solids by their appearances, he was great. Peak of Teneriffe, or even of St. Peter's ly surprised when examining the pictures at Rome, it would be the work of a lifeof solids, to find all the parts plane and time" Besides, its discovery reaches smooth like the rest; he asked which of farther than the touch could carry us; it his senses deceived him, his sight or his enables us to range through the vault of hearing? Being shown a miniature of his Heaven, and determine the motions of father, which was painted on a watch case, the heavenly luminaries. It traces in the he at once perceived that it was a repre- countenance the workings of the mind ; sentation of his father, but expressed it displays the passions and affections of great surprise that so large a counte. the soul With association it is every nance could be contained in so small a thing; without it, it would be useless as space : it appeared to him as impossible the bright fleeting visions of sleep. as for a pint to hold a hogshead. Mr. Sights of a quadrant, &c. thin pieces of Ware published, in the Philosophical brass, raised perpendicularly on its side, Transactions of 1800, a case which seemed or on the index of a theodolite, circumto militate greatly against Mr. C.'s con- ferentor, &c. They have each an aperclusions; Mr. W.'s patient from the first ture, or slit, up the middle, through had ideas of distance and form. But Mr. which the visual rays pass to the eye, and W. himself furnishes a solution of this distant objects are seen. difficulty: for we find, from his paper, SIGN, in algebra, denotes a symbol that his patient had always been able to or character. Mr. Maclaurin observes, distinguish light and vivid colours from that the use of the negative sign, in algesbade.

bra, is attended with several consequenSensations of colour are in the early ces that at first sight are admitted with parts of life very vivid, and assist consi. difficulty, and has sometimes given occaderably in the formation of our mental sion to notions that seem to have no real pleasures; but the other sensations de foundation. This sign implies, that the rived from this sense are principally im. real value of the quantity represented by portant to us, as being by association the the letter to which it is prefixed is to be

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