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subtracted : and it serves, with the posi- ty of the merchant ships under their con. tive sign, to keep in view what elements voy; these are very numerous and imor parts enter into the composition of portant, being all appointed and deterquantities, and in what manner, whether mined by the Lords of the Admiralty, as increments or decrements, (that is, and communicated in the instructions whether by addition or subtraction,) which sent to the commander of every ship of is of the greatest use in this art. See Ne. the treet or squadron before their puiting GATIVE sign.

to sea Some of the principal of which Signs, in astronomy. The ecliptic is are as follow : when a commander in chief usually divided, by astronomers, into 12 would have them unmoor, he looses his parts called signs, each of which, of main-top-sail, and fires a gun, which, in course contains 30 degrees. They are the royal navy is to be answered by every usually called the signs of the zodiac; flag-ship, and every ship is to get un. and beginning at the equinox, where the der sail as soon as she can. When, in Sun intersects and rises above the equa. bad weather, he would have them wear, tor, have these names and marks, Aries and bring to the other tack, he hoists a qp, Taurus 8, Gemini , Cancer oo, pendant on the ensign-staff, and fires a Leo , Virgo mg, Libra -, Scorpio m, gun: then the leeward-most and sternSagittarius 1 , Capricornus , Aquari. most ships are to wear first, and bring on us , Pisces *.. Of these signs, the the other tack, and lie-by, or go on with first six are called northern, lying on the an easy-sail, till he comes ahead. When north side of the equator ; the last six any ship discovers land, he is to hoist his are called southern, being situated to the jack and ensign, and keep it abroad till south of the equator. The signs from the admiral answer him by boisting bis, on Capricornus to Gemini are called ascend. sight of which he is to hawl down his en. ing, the Sun approaching or rising to the sign. If any discovers danger, he is to tack north pole while it passes through them; and bear up from it, and to hang his jack and the signs from Cancer to Sagittarius abroad from the main-top-mast cross trees, are called descending, the Sun, as it and to fire 2 guns : but if he should strike moves through them, receding or de. or stick fast, then, besides the same sigscending from the north pole. See Zo. nal with his jack, he is to keep firing. till DIAC.

he sees all the Acet observe him, and enSign manual. The King's signature is deavour to avoid the danger. When the so called. All commissions in the regu. adiniral would have the vice-admiral to lar army of Great Britain, army warrants, send out ships to chase, he hoists a Aag &c. bear the sign manual. The appoint. striped white and red on the flag staff at ments of officers in the volunteers have the fore-top-mast-head, and fires a gun: been so distinguished during the present but if he would have the rear-admiral do war. Adjutants only in the militia have so, he hoists the same signal on the flagtheir commissions signed by the King; staff at the mizen-top-mast-head, and fires those of the field officers, captains and a gun. When he would have them give subalterns, &c. are signed by the lords over chase, he hoists a white flag on his lieutenants of counties, or by their depu. Aag.staff at the fore-top-mast-head, and ties, for the time being, sanctioned by a fires a gun; which signal is also to be previous intimation from the Secretary of made by that flag-ship which is nearest State, that the King does not disapprove the ship that gives chase, till the chasing of the names wbich have been laid before ship sees the signal. When the admiral him.

would have the feet prepare to anchor, SIGNALS, certain signs agreed upon, he hoists an ensign, striped red, blue, and for suddenly conveying intelligence to white, on the ensign-staff, and fires a gun; places to which the voice cannot reach. and every Aag-slip makes the same sig

Thus, in some countries, fires are lighted nal. upon the hills, at the approach of danger: Besides these, there are many other and at the beginning of a battle or an at. signals used by dayand different signals' tack, signals are usually made with drums upon these and other occasions, used by and trumpets. At sea they are given by night: and others also when a feet sails firing cannon, or muskets, by lights, flags, in a fog; all of which are tu be found in sails, &c.

the Book of Signals. Signals at sea are made by the admiral The signals for managing a sea-fight or commander in chief of a squadron, are also very numerous, the principal of either in the day, or by night, whether which are as follow : when the admiral for sailing, fighting, or the better securi. would have the feet form a line of battle,

one ship a-head of another, he hoists an fore and mizen-top-mast-heads, and fires union-bag at the mizen peak, and fires a a gun; and all the flag-ships are to do gun; and every flag-ship does the like. the same. The fleet being in a line of But when they are to form a line of battle battle, if he would have the ship that one abreast of another, he boists a pen. leads the van hoist, lower, set, or hawl-up dant with the union-flag, &c. When he any of his sails, he spreads a yellow flag would have the admiral of the white, or under that at his main-top-mast-head, and he that commands in the second post, to fires a gin; which signal the flag-ships tack, and endeavour to gain the wind of are to answer; and the admiral will hoist, the enemy, he spreads a white fag linder lower, set, or bawl-up the sail, which he the flag at the main-top-mast.head, and would have the ships that lead the van fires a gun; and when he would have the do; which is to be answered by the fag. admiral of the blue do so, he does the ships of the feet.-When the enemies same with the blue fag. If he would run, and he would have the whole fleet have the vice-admiral of the red do so, he follow them, he makes all the said he can spreads a red Aag from the cap, on the after them himself, takes down the sigmain-top-mast-head downward on the nal for the line of battle, and fires two back-stay ; if the vice-admiral of the blue, guns out of his fore-chase, which the he spreads a blue flag, and fires a gun; if fag-ships answer: and then every ship is he would have the rear admiral of the red to endeavour to came up with, and board do so, he hoists a red flag at the Aag-staff the enemy. When he would have the at the mizen-top-mast-head ; if the rear ad. chase given over, he hoists a white Aag miral of the white, a white Aag; if the at the fore.top-mast-head, and fires a gun. rear-admiral of the blue, a blue flag, and If he would have the red squadron draw under it a pendant of the same colour, into a line of battle, one abreast of anowith a gun. If he would have him that ther, he puts a broad Aag, striped red and commands in the second post of his squad. white, on the Aag.staff at the main-top. ron to make more sail, he hoists a white mast-head, with a pendant under it, and flag on the ensign-staff; but if he that fires a gun; if the white or second squa. commands in the third post be to do so, he dron is to do so, the fag is striped red, hoists a blue Aag, and fires a gun; and all white, and blue ; if the blue or third the flag-ships must make the same signal. Squadron is to do so, the flag is a Ge. Whenever he boists a red flag on the fag- noese ensign and pendant; but if they staff at the fore-top-mast-head, and fires are to draw into a line of battle one a-head a gun, every ship in the feet must use of another, the same signals are made their utmost endeavour to engage the without a pendant. If they are to draw enemy in the order prescribed. When into the line of battle one astern of anohe hoists a white fag on his mizen-peak, ther, with a large wind, and he would and fires a gun, all the small frigates of have the leaders go with their starboard. his squadron, that are not of the line of tacks aboard by the wind, he hoists a red battle, are to come under the stern. If and white flag at the mizen.peak, and the fleet be sailing by a wind in the line fires a gun; but if they should go by the of battle, and the admiral would have larboard-tacks aboard the wind, he hoists them brace their bead sails to the mast, a Genoese flag at the same place; which he hoists up a yellow flag on the flag- signals, like others, must be answered by staff, at the mizen-top-mast-head, and the flag-ships. fires a gun, which the flag-ships are to an. Signals, day, are usually made by flags swer; and then the ships in the rear are and pendants, sometimes accompanied to brace first. After this, if he would have with one or more guns; and night-signals them fall their head-sails, and stand on, he are either lanterns disposed in certain hoists a yellow Aag on the flag-staff of the figures, as lines, squares, and triangles, or fore-top-mast-head, and fires a gun, which are made with false fires. Fog-signals the flag-ship must answer; and then the consist of operations which emit sound, ships in the van must fall first, and stand as firing cannon or musquets, beating on. If, when this signal is made, the red drums, &c. flag at the fore top-mast-head be abroad, SIGNALS, in military actions. In former he spreads the yellow flag under the red times large pieces of wood were hung flag. If the fleets being near one ano. above the towers of cities or castles, ther, the admiral would have all the ships which, by being drawn up or lowered, to tack together, the sooner to lie in a gave intelligence of what passed. This posture to engage the enemy, he hoists method has been succeeded by the inan union-flag on the flag-staves at the vention of telegraphs, which answer every purpose of communication, when they his majesty's hand : it is always in the can be established through any extent of custody of the secretaries of state. country. Besides those signals, there are SILENE, in botany, catch-fly, a genus others which may be called vocal and of the Decandria Trigynia class and order. demi-vocal. The vocal signals are those Natural order of Caryophyllei. Caryo. of the human voice, which consist in the phylleæ, Jussieu. Essential character: necessary precautions that are adopted to calyx ventricose ; petals five, with claws, prevent a guard or post from being sur crowned at the throat; capsules threeDrised, to enounce words of command in celled. There are sixty-six species. action, &c. Of the first description are SILICA, in mineralogy and chemistry, paroles and counter-signs which are ex. is generally found in a stony state, and, changed between those to whom they from its forming nearly the entire compoare entrusted, and which are frequently sition of Aint, it has acquired the name of altered during the day and night, to pre silica, silex, or silicious earth. This earth vent the enemy from receiving any infor- exists in great abundance in nature, and mation by means of spies. The demi- it constitutes the basis of some of the vocal signals are conveyed by military in- hardest stones of which the nucleus of the struments; the different soundings of globe consists; and, on account of its which indicate, instantaneously, whether great abundance, it has been regarded as an army is to halt or advance, whether the primitive or elementary earth, the troops are to continue in the pursuit of an base of all the other earths. enemy, or to retreat.

Silica forms one of the constitue nt parts The demi-vocal signals, directed to be of most stony bodies; but it exists in observed in the British service, as far as greatest abundance in agates, jasper. regards the maneuvring of corps, &c. flints, quartz, and rock crystal: in the lat. consist of signals for the government of ter it exists nearly in a state of purity. light infantry, and of cavalry regiments, To obtain it perfectly pure, a quantity of squadrons or troops : the latter are pro. quartz, or rock crystal, may be exposed perly called soundings. Lightinfantry sig- to a red heat. When it is taken from the nals are to give notice to advance, to re- fire, and while it is yet hot, it is suddenly treat, to halt, to cease firing, to assemble, immersed in cold water. It is then to be or call in all parties. In the regulations reduced to powder, and if transparent printed by authority it is observed, that rock crystal has been employed, it is then these signals are to be always considered in a state of tolerable purity. To have it as fixed and determined ones, and are ne- perfectly pure, mis one part of the ver to be changed. The bugle horn of pounded stone with three parts of potash, each company is to make himself perfect and expose them in a crucible to a heat master of ihem. All signals are to be re- which is sufficient for the fusion of the peated; and all those signals, which are mixture. The mass thus obtained is so. made from the line or column, are to con- luble in water. Add a sufficient quantity vey the intention of the commanding offi- of water for its solution, and drop in mu. cer of the line to the officer commanding aritic acid as long as there is any precithe light infantry, who will communicate pitate. Let this be repeatedly washed them to the several companies or detach. with water and dried. The substance ments, either by word or signal.

thus obtained is pure silica. It is in the SIGNATURE, in printing, is a letter form of very fine white powder, which put at the bottom of the first page, at least, has neither taste nor smell. The parti. in each sheet, as a direction to the bind- cles are rough and harsh to the feel, as er, in folding, gathering, and collating when they are rubbed between the finthem. The signatures consist of the capi. gers, or touched with the tongue. The tal letters of the alphabet, which change specific gravity is 2.6. Light has no acin every sheet: if there be more sheets tion on silica, and it is one of the peculiar than letters in the alphabet, to the capital characters of this earth, that it resists, letter is added a small one of the same unchanged, the greatest degree of beat. sort, as A a, Bb; which are repeated as There is no action between silica and often as necessary. In large volumes it is oxygen azote, or hydrogen; nor is it usual to distinguish the number of alpha- changed by exposure to the air. It is not bets, after the first two, by placing a figure acted upon by carbon, phosphorus, or before the signature, as 3 B, 4 B, &c. sulphur. It is insoluble in water; but, in

SIGNET, one of the king's seals, made a state of minute division, it absorbs a use of in sealing his private letters, and considerable portion, and forms with this all grants that pass by bill signed under liquid a transparent jelly. When it is

exposed to the air, the whole of the mois. to very strong heat, they melt into a white ture is evaporated.

enamel. But the most important com. Silica is frequently found in nature in pounds of the earths are those of silica the crystallized form, and then it is dis. and alumina. These earths may be comtinguished by the name of rock crystal. bined together, as appears from the ex. It is most commonly in hexagonal prisms, periments of Guyton, in the humid way. terminated by hexagonal pyramids. Crys. He mixed together equal parts of alumina, tals of silica have also been formed arti. dissolved by means of potash, and of silica ficially. In a solution of silica in fluoric held in solution by the same alkali. When acid, which had remained at rest for two the solutions came into contact, a brown years, Bergman found crystals, some of zone was immediately formed, which which were cubes, and some had trun. spread, by agitation, through the whole cated angles, at the bottom of the vessel. mass, and communicated to it a yellowish Crystals of silica have also been formed, colour. The mixture was no further by diluting largely with water the com changed during the space of an hour, al. bination of silica and potash, and allow though it was occasionally stirred with a ing it to remain for a long time.

glass rod; but at the end of that time the Silica is only acted on by a very few of whole mass assumed the appearance of a the acids. These are the phosphoric and thick, opaque, white jelly. When the siboracic, which combine with it by fusion, lica and alumina are mixed together, and and the fuoric, which dissolves silica formed into a paste with water, and exeither in the gaseous or liquid state. posed to beat, they strongly cohere, and When silica is held in solution in water assume a considerable degree of hardby means of an alkali, it is also dissolved ness. This compound forms the basis of by the muriatic acid. The alkalies have all kinds of pottery and porcelain. a very powerful action on this earth. In Barytes and strontian in some degree the preparation of the pure earth, it was dissolve silica as the alkalies do. Two combined with potash by means of fusion. hundred parts of strontian, with sixty of This compound is different in its nature silica, heated intensely in a crucible for and properties, according to the propor an hour, produced a grey sonorous rifty tions of the silica and the alkali. Two or mass, with only a slight caustic taste. three parts of potash, with one of silica, This, being boiled in water, was partly form a compound which is deliquescent dissolved, but could not be crystallized. in the air, and soluble in water. This was Saturated with nitric acid, it gave, by formerly distinguished by the name li- evaporation, a copious jelly, which was quor silicum, or liquor of Aints. It is now pure silex. A similar result was obtaincalled silicated alkali. When this solu. ed when barytes was used instead of tion is long exposed to the air, the earth strontian. is deposited in a flaky gelatinous form. It S ILIQUA, in botany, a species of pod, is decomposed by acids, which combine in which the seeds are alternately fixed with the alkali, and the pure earth falls to either suture or joining of the valves; to the bottom in the state of fine powder. in this it differs from the legumen, which When the solution is largely diluted with has its seeds attached to one suture only. water, and if a greater quantity of the This kind of seed-vessel is found in all acid be added than is sufficient to saturate the class Tetradynamia of Linnæus. See the alkali, the silica remains in solution. LEGUMEN. This is particularly the case when the SILIQUOSÆ, in botany, the name of muriatic acid is employed; but when the the thirty-ninth order in Linnæus's Fragsilica is in greater proportion, a com. ments of a Natural Method, consisting of pound is formed which is possessed of plants that have a siliqua for a seed-ves. very different properties. The substance sel. It is divided into two sections : 1. thus obtained is glass. This earth also Those which have cross-shaped Aowers enters into combination with some of the with long pods, as the brassica, cabbages, earths. If to a solution of the liquor of raphanus, radish, sinapis, mustard, &c. flints lime-water be added, a precipitate 2. Those with cross-shaped flowers with is formed, which is found to be a com. short rounds pods, as the iberis, candypound of silica and lime. Silica also com- tuft. This order chiefly furnishes bien. bines with lime by means of heat, and in nial and perennial herbs of an irregular certain proportions a glass is formed. figure. The roots are long, branched, Silicious earth enters with difficulty into crooked, and fibrous; those of the turnip combination with magnesia ; but if equal and radish are succulent and Aeshy; the parts of silica and magnesia be exposed flowers are hermaphrodite, and in the

VOL. XI.

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greater number disposed in a spike at the of silk within his dominions; for which extremity of the branches. They are purpose he employed two monks, who easily rendered double by culture. The bad been in India, to procure the eggs of siamina are six in number, two of which the inscct from China. This was accomare of the length of the calyx, and the plished about the year 555; the eggs remaining four somewhat longer, but were hatched at Constantinople, and the shorter than the petals. The seed-ves- breed of the insect being carefully ensel, as we have observed, is a long pod couraged, raw silk was soon produced in in plants of the first section ; a short and abundance, which was worked up into round one in those of the second. The manufactures at Athens, Thebes, Corinth, seeds are roundish, small, and attached and other places. It appears, however, alternately by a slender thread to both that for many years after the establishsutures, or joining of the valves.

ment of the culture of silk in Greece, SILK, the web or envelopement of the garments of this material continued to be caterpillar, of a species of moth called very highly valued ; as, about the year the Phalena mori; which, being converti. 790, Charlemagne sent two silken vests ble to various purposes of utility and as a present to Offa, king of Mercia. elegance, forms an important article in About the year 1130, the silk manufaccommerce, as the material of a valuable ture had made such progress in the island manufacture. The caterpillar, or silk. of Sicily as to excite the jealousy of the worm, when full grown, encloses itself Venetians, from its interfering with their in a loose web, in the midst of which it importations of silks from Greece.-From forms a much closer case or covering, of Venice and Sicily the silk manufacture an oval form, and varying in colour from spread through Italy, from whence it was white to a deep orange, but usually of a introduced into the southern provinces of bright yellow colour. In this case, or France. ball, the animal becomes a chrysalis, and As soon as the worms have produced remains enclosed about fifteen days; their balls, or cocoons, they become an when, having resumed active life, in the article of trade, for in those countries form of a moth, it makes a hole at one where silk is cultivated few persons reel end of its prison and comes out. This, off their cocoons, but sell them to others, as it destroys the silk ball, is prevented, who make this operation a separate busiin those countries where silk is cultivat. ness. The silk, as formed by the worm, ed, by killing the chrysalis by means of is so very fine, that if each ball, or heat. See PHALENA,

cocoon was reeled separately, it would The silk-worm is supposed to be a na be totally unfit for the purposes of the tive of China, at least the Chinese were manufacturer; in the reeling, therefore, the first nation in the world acquainted the ends of several cocoons are joined with the manufacture of silk. It was lit. and reeled together out of warm water, tle known in Europe before the time of which, softening their natural gum, makes Augustus. Galen, who lived about the them stick together, so as to form one year 160, mentions silk as in use no strong smooth thread. As often as the where but at Rome, and only among the thread of any single cocoon breake, or rich. The Emperor Heliogabalus, who comes to an end, its place is supplied by died in the year 220, is said to have been a new one, so that, by continually keepthe first man that wore a holosericum, or ing up the same number, the united dress made wholly of silk ; princes, as thread may be wound to any length: well as subjects of the greatest quality, the single threads of the newly added cowearing only a stuff made of silk mixed coons, are not joined by any tie, but with other materials. In the time of simply laid on the main thread, to which Aurelian, silk was sold in Rome for its they adhere by their gum; and their ends weight in gold, and long continued to are so fine as not to occasion the least bear a great value, from the expense perceptible unevenness in the place attending the mode in which it was pro- where they are laid on. The apparatiis cured. The only silk then known was for reeling consists merely of a small that of China, which was brought from open kettle of water, under which is a thence, in the raw siate, to Berytus and fire to keep it hot, and a reel of a very Tyre, in Phænicia, where it was mad!l. simple construction. Care should be factured ; but this branch of commerce taken in the operation, that the silk wlien being interrupted by the conquests of reeled off may consist of a smooth thread, the Scythians, the Emperor Justinian be. of equal thickness and strength, not fat, came desirous of establishing the culture but of a round form, liaving the singl

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