A long range of mountains, all included in the Sudetic chain, but bearing different names, such as the Riesengebirge, the Glatz mountains, Moravian mountains, &c., divides Silesia from Bohemia and Moravia. From Hungary it is separated by the Carpathians. The Sudetic range is steep, and full of narrow defiles, particularly on the north-west; they become broader as they stretch to the southward. So great an extent of high ground renders the climate on the whole cold; the whole south of Silesia being often covered with snow, while at Breslau, and farther north, the progress of spring is sensibly felt. The Oder is the next great natural feature of Silesia, and, flowing from south to north, traverses it nearly in the middle, passes Breslau, and receives all the lesser rivers flowing from east and west. To the east the country is called the Polish side: it is perfectly level, with a soil often sandy, marshy, and unproductive; while the western or German side, though hilly, is cultivated by a more improved race, and is superior both in mineral and vegetable products. It is in fact one of the best portions of the Prussian territory, containing mines of coal and iron, and, on a smaller scale, copper, vitriol, and cobalt mines. This is likewise a great manufacturing country, linen manufactures being as general here as in Normandy or the north of Ireland: the value annually made is estimated at £1,500,000 sterling, of which more than half is exported. Attention is consequently bestowed on the culture of flax, the quality of which is equal to that of any part of the world. The wool has also been improved since the latter part of the eighteenth century. Foxes and other beasts of game abound: and the lynx, as well as the beaver, is sometimes found in the mountains. The forests are of great importance to the local manufactures, affording abundant fuel.

It is also a received notion that the water on the Silesian side of the Sudetic range is better for bleaching than that on the Bohemian side. The spinning of flax, for so large a manufacture, occupies a great number of hands: in many houses it is the sole occupation; and scarcely anywhere is there a family where some person is not employed in spinning or weaving it. The distaff, and not the wheel, is generally employed; and all is carried on with a very limited capital,

there being here no factories or collective establishments.

Woollens are likewise a considerable object of manufacture, but they are in general coarse, and the value made is computed at little more than £500,000 sterling: they are made chiefly at Goldberg and Grunberg. Cotton works arose here in the latter part of the eighteenth century, and hardware has been extensively made only about the same period. The tanneries are hardly enough to supply the consumption. The total annual value of manufacture is computed at £3,000,000 sterling. In these, and the raw produce, coal, timber, and madder, Silesia carries on a considerable traffic. The imports are hemp, lintseed, and hides from Russia; wine, potash, and hardware from Austria; colonial produce, gilk, and the fruits of southern climates from different countries, almost all through the medium. of the Oder.

The Silesians are in general of good moral habits, with little information, credulous and superstitious, impressed with a blind veneration for aristocracy and etiquette. The gentry, or, as they are styled, the noblesse, are numerous and poor as in any part: a number of them find employment in the military service. The Reformation was introduced here early. In 1609 Rodolph II. found it necessary to grant the Protestants full liberty of conscience: his successors, however, revoked the concession, the effect of which was to deprive Silesia of a number of its inhabitants. In 1708, when the Swedes under Charles XII. overran Poland, occupied Saxony, the emperor, to ward off this assailant, consented to restore to the Protestants of Silesia the free exercise of their worship: on the conquest of Silesia by Frederick II. he put all religious creeds on an equal footing. The proportion of Protestants, long inferior to that of Catholics, has of late begun to exceed it: of Jews the number in Silesia is about 12,000.

A number of parish schools have been founded by the aid of government; but, on the eastern or Polish side, much ignorance prevails. At Breslau there is a university, partly Protestant, partly Catholic. In the provincial towns there are gymnasia or high schools, Protestant colleges, and seminaries for educating Catholic priests. The common language of the country is German, but in the mountainous districts, and on the tracts. bordering on Poland, the ancient dialect of the country, which is a mixture of the Polish and Bohemian, is preserved.

The tribes called the Quadi and Lygii seem to have first peopled Silesia, and to have yielded in. the sixth century to a Sclavonic tribe, who adopted the name of Zlesy. At present the Polish name of this country is Zlesien, and it was long a province of Poland. It was afterwards ceded to the sons of Boleslaus II., an expelled king of Poland, in the eleventh century; and, being thus divided and subdivided, was without much difficulty subdued by the kings of Bohemia in the fourteenth century; the crown seizing, as vacant fiefs, the possessions of such of the great families as became extinct. Silesia passed with Bohemia to the house of Austria, in the early part of the sixteenth century, and continued in its undis

turbed possession until the death of Charles VI. in 1740, when Frederick II., who revived a long dormant claim to the western part of Silesia, viz. the principalities of Liegnitz, Brieg, and Wohlau, supported it by an immediate invasion. Austria took up arms, and, on being attacked on another side by Bavaria and France, received the aid of England. The result was a contest, conducted with alternate success, but terminated, as far as regarded Silesia, by the cession of that country to Prussia. But the house of Austria had no intention of definitively relinquishing it. It formed in 1756, against Prussia, a coalition of France, Russia, Saxony, and Sweden, which threatened the entire subversion of that kingdom: a danger from which she was saved by the talents of her sovereign, the aid of England, and heavy sacrifices of her wealth and population. The peace of Hubertsburg, in 1768, left Silesia in the hands of Frederick. It was now allowed to breathe from its ravages, and enjoyed a peace of forty years, inviting colonists from Germany and Poland to repair the havock of war. In 1807 it was overrun by the French.

SILESIA, AUSTRIAN, that part of Silesia retained by Austria in 1742, has an area of 1845 square miles, with nearly 350,000 inhabitants. It is divided into the circles of Troppau and Teschen, and is completely incorporated with Moravia, being subject to the same civil courts, and the same military administration. It is hilly, and does not produce a sufficiency of corn for the population ; but has good pasturage, abundance of flax and hemp, and flourishing linen and woollen manufactures. See MORAVIA. SILESIAN EARTH, in the materia medica, a fine astringent bole. It is very heavy, of a firm compact texture, and in color of a brownish yellow. It breaks easily between the fingers, and does not stain the hands; is naturally of a smooth surface, is readily diffusable in water, and melts freely into a butter-like substance in the mouth. It leaves no grittiness between the teeth, and does not ferment with acid menstrua. It is found in the perpendicular fissures of rocks near the gold mines at Strigonium in Hungary, and is supposed to be impregnated with the sul phur of that metal. It is a good astringent, and better than most of the boles in use.

SILHET (Srihata, a rich market), a district in the province of Bengal, situated principally between 24° and 25° of N. lat. To the north and east it is bounded by a lofty ridge of mountains inhabited by many wild tribes; on the south by Tipperah and Mymunsingh; and it has Mymunsingh to the west. In 1784 it contained 2861 square miles, and the revenue was only 233,924 rupees.

It is the most easterly of the Company's possessions in Hindostan, being within 350 miles of the province of Yunan in China. Although so near to this rich empire, no sort of intercourse subsists betwixt them, the intermediate country being a confused mass of mountains covered with jungle, and inhabited by some of the most uncivilised tribes in Asia. This region has been examined only a very short way from the frontiers of Silhet; but, from the most consistent accounts supplied by the natives, there is reason

to believe the intervening space is destitute of navigable rivers, without towns or villages, and wholly trackless. These difficulties, however, are not insurmountable, and it is to be hoped the Bengal government will not leave it much longer unexplored.

Under the Mogul government, Silhet was formed into a foujedarry, or military station, more on account of its remote and secluded situation, beyond the Brahmapootra and Soormah, than from any reasonable apprehensions of foreign invasion, protected as it is by inaccessible hills, or impenetrable jungles. Its actual dimensions, since the dismemberment of several pergunnahs, are computed at 2861 miles, divided into 146 small pergunnahs, held by about the same number of zemindars. Near to the town of Silhet the country presents a novel appearance to an eye long habituated to the flat surface of the lower districts of Bengal. It is composed of a number of irregularly insulated hills, placed at a short distance from each other, and covered with trees and verdure to their summits; while to the north and east lofty mountains rise abruptly like a wall, to the height of several thousand feet, and appear as if they had, at some remote period, withstood the surge of the ocean.

During the rains the greater proportion of the land is laid under water, by the overflowing of the Soormah and other rivers, by which it is intersected, and the passage from Dacca is performed for nearly the whole way over rice and pasture fields, which in the cold season are perfectly dry. Over this tract, when the floods are at their height, there is above ten feet of water; the elevated sites of the villages appear like islands; the masts of the vessels are entangled with the branches of trees, while their progress is impeded by the thickness and adhesion of the paddy stalks. When the inundation drains off, the land is left in an excellent condition for rice cultivation; food of all sorts is consequently remarkably cheap-the average price of rice per rupee being four or five maunds (of 80 lbs. each), and coarser grains still cheaper. In addition to this supply every stream and puddle swarms with fish, which are caught, with scarcely any trouble, with a small hand net, or even a piece of a mat. As may be supposed, wages are extremely low, being from half a rupee to one rupee and a quarter per month; but the laborers being naturally averse to exertion, and never working but when stimulated by hunger, the country is on the whole very indifferently cultivated. The necessaries of life being so very cheap, there is little occasion for gold and silver coins-a more minute subdivision of value being required; the whole rents are consequently paid in cowries, which are the medium also of commercial transactions. Formerly large boats were built here for the royal fleet stationed at Dacca, and squarerigged vessels have also been occasionally constructed. The chief export from Silhet is chunam or lime, which is found in inexhaustible quantities; and hence Calcutta, and the most remote stations in Bengal, are furnished with that article. Another principal export is cargoes of orangesa

considerable tract of country consisting almost entirely of orange plantations, the fruit of which

sells on the spot at 1000 for a rupee. The other productions are aguru or fragrant aloe wood, and a manufacture of wild silk, named muggadooties. Great numbers of elephants are also caught in this district, but their quality is inferior to those caught near the sea coast. Silhet and Azmerigunge are the chief towns, and the Soormah and Megna the principal rivers. In 1801, when an investigation respecting the population of Bengal took place, this district was found to contain 492,495 inhabitants, in the proportion of two Mahometans to three lindoos.-J. Grant, Rennell, &c.

SILHET, a town in the province of Bengal, the capital of a district of the same name. Lat. 24° 55' N., long. 91° 40′ E. The travelling distance from Calcutta to Silhet is 325 miles, the direct distance 260.

SILHOUETTE, in drawing, a new French word, signifying a profile taken in shade. In a late translation of Lavater's Physiognomy, by the Rev. Dr. C. Moore (Lond. 8vo. 1797), this word is often used, but is never once translated, or its derivation mentioned; whence it would seem that the doctor considers it as already adopted into the English language, at least among connoisseurs.

SILICA, in chemistry and mineralogy, one of the primitive earths, which in consequence of Sir H. Davy's researches on the metallic bases of the alkalis and earths, has been recently regarded as a compound of a peculiar combustible principle with oxygen. If we ignite powdered quartz with three parts of pure potash in a silver crucible, dissolve the fused compound in water, add to the solution a quantity of acid, equivalent to saturate the alkali, and evaporate to dryness, we shall obtain a fine gritty powder, which being well washed with hot water, and ignited, will leave pure silica. By passing the vapor of potassium over silica, in an ignited tube, Sir H. Davy obtained a dark-colored powder, which apparently contained silicon, or silicium, the bases of the earth. Like boron and carbon, it is capable of sustaining a high temperature without suffering any change. Aqueous potash seems to form with it an olive-colored solution. But, as this basis is decomposed by water, it was not possible to wash away the pot ash by this liquid. Berzelius and Stromeyer tried to form an alloy of silicon or silicium with iron, by exposing to the strongest heat of a blast furnace, a mixture of three parts iron, 1.5 silica, and 0.66 charcoal. It was in the state of fused globules. These, freed from the charcoal, were white and ductile, and their solution in muriatic acid evolved more hydrogen than an equal weight of iron. The specific gravity of the alloy was from 6-7 to 7-3, while that of the iron used was 7-8285. From Mr. Mushet's experiments, however, as well as from the constitution of plumbago, we know that carbon will combine with iron in very considerable proportions, and that in certain quantities it can give it a whitish color and inferior density. Nothing absolutely definitive, therefore, can be inferred from these experiments.

M. Berzelius has lately obtained pure silicium by the combustion of potassium in silicated fluo

ric gas; as also by the action of potassium on the double fluate of silica and potash, or of silica and soda. The latter salt having the advantage of containing a greater quantity of fluate of silica, under the same weight and bulk, deserves the preference. The salt is easily prepared by saturating aqueous silicated fluoric acid with carbonate of soda, when the very sparingly double salt precipitates, which is to be washed and dried, at a temperature considerably above 212° Fahrenheit. This dry matter in fine powder is to be stratified, with thin slices of potassium, in a glass tube sealed at the end, which is to be uniformly heated at once with a spirit flame. Even before ignition the silicium is reduced with a slight hissing sound, and some appearance of heat. No gas is disengaged when the salt has been well dried. The mass is allowed to cool. It is hard, agglutinated, porous, of a deep brown color, which does not alter in the air, merely exhaling the smell of hydrogen, as manganese does when pressed between the fingers or breathed upon. It is to be washed with water in successive quantities to remove the fluate of potash that is formed. Some gas is disengaged, but this soon ceases, and, though the water be raised to ebullition, the brown powder does not decompose it. The solution obtained by ebullition being very acid, the substance is to be boiled with new portions of water till the liquid manifests no signs of acidity, when it is to be passed through a filter. The powder, being dried, is of a chestnut brown (maroon) color, containing visibly heterogeneous points of a brighter hue. The first of the above washings should be with a large quantity of water, so that the liquid which becomes alkaline by the oxidisement of the potassium, may be so dilute as to have no tendency to oxidise the silicium and to dissolve it. For this reason the mass must not be treated with hot water till all the alkalinity be removed. It is thereafter to be treated with boiling water, till a drop of this leaves no stain on evaporation. This process requires much time, and a large body of water.

Silicium, obtained by this process, contains some hydrogen, but in less quantity, and probably in the same way as the charcoal of wood, which Sir H. Davy regards as hydrogenated carbon. It contains, besides, some silica, which proceeds from a small portion of the potassium getting oxidised at first, and in this state separating a little silica from the double salt. The hydrogenated silicium is to be heated for some time almost to redness in an open crucible, then it is finally to be ignited. Should the silicium offer to take fire, the crucible is to be instantly covered, and the heat lowered, which will immediately stop the inflammation. After this calcination, the silicium is incombustible in the air, and may be washed from its adhering silica by pure liquid fluoric acid, taking care that no iron or manganese is present; for the alloy thence resulting would dissolve entirely with disengagement of hydrogen. After being treated with this acid, the silicium is to be washed and dried. Obtained in this way, silicium has a deep nutbrown color, but not the least metallic lustre. When rubbed with a steel burnisher, it presents no

trace of brilliancy, opposing a resistance to friction, like an earthy substance. It is incombusti. ble in the atmospheric air, and in oxygen gas. It suffers no change in the flame of the blowpipe, apparently belonging to the most infusible class of bodies. These properties appear at variance with what takes place with the silicium immediately after its reduction by potassium, for it readily burns. M. Berzelius ascribes this difference to the presence of hydrogen in the latter substance, which may be regarded as a siliciuret of potassium at first, and after simple washing a hydruret of silicium. Ignition, well regulated, expels the hydrogen, without setting the compound on fire; but, if hastily induced, the hydrogen kindles the silicium, which then becomes covered with a coat of silica. The condensation which the silicium undergoes by ignition is the cause of its becoming insoluble in fluoric acid.

Silicium stains and sticks strongly, even when dry, to the glass vessels in which it is kept.

Silicium does not conduct electricity. After its ignition it is not affected by chlorate of potash, even at a red heat: nor by nitre, till the temperature has become high enough to decompose the nitric acid, and to allow the affinity of its alkaline base to act. At a white heat nitre attacks it violently.

With carbonate of potash silicium burns very readily with a lively flame. Gaseous oxide of carbon is disengaged, and the mass blackens from intermixture with charcoal. By taking a small proportion of carbonate of potash, or of soda, as one-half the bulk of the silicium, the inflammation takes place much below ignition. With larger proportions of the carbonate, the mass swells up from the development of the gaseous oxide of carbon, takes fire, and burns with a blue flame. With a still greater proportion there is no sign of combustion; the mass does not blacken, but merely exhales the above gaseous oxide. If the incombustible silicium be heated to moderate redness on platinum foil with nitre, no effect ensues; but, if a bit of dry carbonate of soda be made to touch the silicium, a detonation will take place at the expense of the carbonate, and the mass will retain for some time its black color.

Silicium explodes with lively incandescence with the hydrated fixed alkalis at their melting temperature, much below a red heat. Hydrogen is disengaged, which burns visibly when the bulk of the materials is not too small. The same phenomenon takes place with hydrate of barytes. With acid fluate of potash, silicium explodes at the melting point of the salt, which is far under ignition. It is not altered by borax in a state of fusion. Silicium, heated to distinct redness in the vapor of sulphur, takes fire and burns, but much less vividly than in oxygen; but the combination will not take place with the incombustible silicium. In moist air, sulphuret of silicium diffuses a strong smell of sulphureted hydrogen, and speedily loses all its sulphur; but in dry air it may be preserved for a long time. At a red heat, it is roasted, affording sulphurous acid and silica.

Siliciuret of potassium combines readily at a

red heat with sulphur, constituting a true double sulphuret of a deep brown or black color. Simple sulphuret of silicium, when thrown into water, dissolves immediately, with disengagement of sulphureted hydrogen. The silicium changes into silica, which dissolves in the water, and if this be in small quantity, such a concentrated solution may be obtained as to gelatinise after a slight evaporation, and to leave silica, after drying in a transparent cracked mass. It is remarkable to see silica dissolve in such a large proportion in water, at the instant of its formation, and to lose this property by evaporation to such a degree as to become insoluble in acids. This solubility may explain the origin of the crystallisations of silica in drusy cavities, which in many cases could not contain a volume of liquid appreciably larger than that of the crystals themselves. Berzelius did not succeed in combining silicium with phosphorus.

When silicium is heated in a current of chlorine, it takes fire, and continues to burn. If the gas contain some atmospheric air, silica remains in a slender skeleton form. Silicium burns equally well in chlorine, whether or not it had previously been deprived of its combustibility in air. The product condenses into a liquid, which is yellowish with excess of chlorine, but colorless when this is expelled. This liquid is very fluid; it evaporates almost instantaneously in the open air, affording white vapors, and leaving a little silica. It has a very penetrating odor, which may be compared to that of cyanogen. Thrown into water, it floats, then dissolves in it, and leaves some silica. When silicium is heated in vapor of potassium, it takes fire, producing a compound of silicium and potassium. The iodide of potassium does not unite with silicium.

Silicium is neither dissolved nor acted upon by the sulphuric, nitric, and muriatic acids, nor even by the nitro-muriatic. But it dissolves rapidly even in the cold, in a mixture of nitric and fluoric acid, with disengagement of nitrous gas. Combustible silicum dissolves on digestion in water of caustic potash; but in its incombustible state it is not affected by the alkalis in the moist way.

Once insulated, silicium combines very reluctantly with the metals. Its remarkable affinity for platinum is known, from the experiments of M. Boussingault; but it may be heated as often and as long as we please in a platinum crucible, without any combination taking place. But when we try to reduce silicium (from silica) by potassium, in a platinum crucible, the silicium penetrates deeply into the platinum, in the spot where the potassium presses. 100 parts of pure silicium, dried in vacuo, were heated with carbonate of soda. The mass, treated with muriatic acid, evaporated to dryness, and strongly heated, was then dissolved in water. It left silica colored gray by charcoal, which, being washed and ignited, became snow-white, and weighed 203.75 parts. A little silica was afterwards procured from the washings, making in all 205.25. Hence 100 parts of silicium had absorbed 105-25 of oxygen. In another experiment, 208 parts of silica were obtained from 100 of silicium. Hence silica consists of

Silicium does not seem to belong to the metallic class of bodies, but rather resembles carbon and boron. Some philosophical methodists, says Berzelius, will consequently give it the name of silicon; but I regard this denomination as useless, since there is no true limit between the metals and the metalloids (such as boron and carbon). Carbon has the metallic lustre, and conducts electricity, and still it is not reckoned a metal. If silicium could be fused, it would possibly acquire the properties wanting in its pulverulent state. Uranium, in this form, can hardly be distinguished by its aspect from silicium; but when crystallised, it has the metallic lustre. Columbium and titanium approach also to silicium in their chemical properties. Finally, when the electrical relation of a body is regarded as its only decisive feature, it is indifferent whether we place a combustible body among the

metals or not.-Annales de Chim. et. Phys. xxvii. 337.

Mr. Smithson has ingeniously suggested, that silica might be viewed in many mineral compounds as acting the part of an acid. This, however, is a vague analogy, and cannot justify us in ranking silica with acid bodies. When obtained by the process first described, silica is a white powder, whose finest particles have a harsh and gritty feel. Its specific gravity is 2.66. It is fusible only by the hydroxygen blowpipe. The saline menstruum formed by neutralising its alkaline solution with an acid is capable of holding it dissolved, though silica seems by experiment to be insoluble in water. Yet in the water of the Geyser spring a portion of silica seems to remain dissolved, though the quantity of alkali present appears inadequate to the effect. Silica exists nearly pure in transparent quartz or rock crystal. It forms also the chief constituent of flints. By leaving a solution of silica in fluoric acid, or in aqueous potash, undisturbed for a long time, crystals of this earth have been obtained. The solution in alkaline lixivia is called liquor silicum. Glass is a compound of a similar nature, in which the proportion of silica is much greater. Mr. Kirwan made many experiments on the mutual actions of silica and the other earths, at high degrees of heat. The following are some of his results :Effects.