SILK

laboured in a foreign climate; a suflBcient number of butterflies were saved to propagate the race, and mulberry trees were planted to afford nourishment to the rising generations. A new and important branch of industry was thus established in Europe. Experience and reflection gradually corrected the errors of a new attempt; and the Sogdoite amba adors acknowledged, in the succeeding reign, that the Romans were not inferior to the natives of China in the education of the insects, and the manufacture of silk. (Gibbon, Decline and Fall, vol. vii. p. 99.) Greece, particularly the Peloponnesus, was early distinguished by the rearing of silkworms, and by the skill and succe with which the inhabitants of Thebes, Corinth, and Argos carried on the manufacture. Until the 12th century, Greece continued to be the only European country in which these arts were practised; but the forces of Roger, king of Sicily, having, in 1147, sacked Corinth, Athens, and Thebes, carried off large numbers of the inhabitants to Palermo, who introduced the culture of the worm and the manufacture of silk into Sicily. From this island the art spread into Italy; and Venice, Milan, Florence, Lucca, . were soon after distinguished for their succe in raising silkworms, and for the extent and beauty of their manufactures of silk. {Gibbon, vol. x. p. 110.; Biographic Universelle, art. " Roger II.") The manufacture of silk appears to have been introduced into Spain at a very early period by the Moors, particularly in Murcia, Cordova, and Granada. " The last town, indeed, po e ed a flourishing silk trade when it was taken by Ferdinand in the 15th century. The French having been supplied with workmen from Milan, commenced, in 1521, the silk manufacture; but it was not till 1564 that they began succe fully to produce the silk itself, when Traucat, a working gardener at Nismes, formed the first nursery of white mulberry-trees, and with such succe that in a few years he was enabled to propagate them over many of the southern provinces of France. Prior to this time, some French noblemen, on their return from the conquest of Naples, had introduced a few silkworms with the mulberry into Dauphiny; but the busine had not prospered in their hands. The mulberry plantations were greatly encouraged by Henry IV.; and since then they have been the source of most beneficial employment to the French. James I. was most solicitous to introduce the breeding of silkworms into England, and in a speech from the throne he earnestly recommended his subjects to plant mulberry-trees; but he totally failed in the project. This country does not seem to be well adapted to this species of husbandry, on account of the great prevalence of blighting east winds during the months of April and May, when the worms require a plentiful supply of mulberry-leaves. The manufacture of silk goods, however, made great progre during that king's peaceful and pompous reign. In 1629 it had become so considerable in London, that the silk throwsters of the city and suburbs were formed into a public corporation. So early as 1661 they employed 40,000 persons. The revocation of the edict of Nantes, in 1685, contributed in a remarkable manner to the increase of the English silk trade, by the influx of a large colony of skilful French weavers, who settled in Spital fields. The great silk throwing mill mounted at Derby, in 1719, also served to promote the extension of this branch of manufacture; for soon afterwards, in the year 1730, the English silk goods bore a higher price in Italy than those made by the Italians, according to the testimony of Keysler. It would be impo ible, within our limits, to give an account of the gradual progre of the silk manufacture from that period down to the present time. Upon this subject, the reader will find ample details in the Commercial Dictionary; meantime we may remark, that a great revolution was effected in the manufacture in 1825. Previously to that epoch the legislative enactments with respect to it were the most contradictory and impolitic that can well be imagined. The importation of foreign silks was prohibited under the severest penalties; but the advantage that this prohibition was believed, though most erroneously, to confer on the manufacturer, would, under any circumstances, have been more than neutralized by the imposition of oppre ive duties on the raw material. This vicious system was productive of a twofold mischief; for, by teaching the manufacturers to depend on custom-house regulations for protection against foreign competition, it made them indifferent about new discoveries and inventions, while, owing to the exorbitant duties on the raw material, and the want of improvement, the price of silks was maintained so high as to restrict the demand for them within comparatively narrow limits. In 1825, however, a new and more reasonable order of things was introduced. The duties on the raw material were greatly lowered; at the same time that foreign silk goods were allowed to be imported on payment of a duty of 30 per cent, ad valorem. This new system was vehemently 1113 SILVER. opposed at Its outset, and it was confidently predicted that it would occasion the ruin of the manufacture; but the result has shown the soundne of the principles on which it was bottomed. The manufacturers were now, for the first time, compelled to call all the resources of science and ingenuity to their aid; and the result has been that the manufacture has been more improved during the last dozen years than it had been in the whole previous century, and that it has continued progre ively to increase. The total quantity of raw silk imported for home consumption in 1838 was 3,595,816 lbs. The total number of individuals directly engaged in the manufacture has been estimated at upwards of 207,000; but we incline to think that this is very decidedly beyond the mark. The value of the silks annually produced may, perhaps, be estimated at from 10,000,000^. to 12,000,000/. (For full particulars as to the history and manufacture of silk, see Porter's treatise on the subject in Lardner's Cyclopcedia.) SILL. (Sax. fyl.) In Architecture, the horizontal piece at the bottom of a framed case, such as that of a door or window. This word is also used to denote the bottom piece of a quarter partition. Ground sills are those timbers on the ground on which are placed the posts and superstructure of a timber building." Sl'LLlMANITE. A mineral named after Profe or Silliman, from Say brook in Connecticut; it is of a brown or dark grey colour, and composed of silica and alumina, with a trace of oxide of iron. SILT. The name given to the sand, clay, and earth which accumulate in running waters. SILU'RIAN. The name given by Murchison to a series of rocks forming the upper subdivision of the sedimentary strata found below the old red sandstone, and formerly designated the greytvacke series. These strata are well developed in that part of England and Wales formerly included in the ancient British kingdom of the Silures. See Geology. SILU'RIDANS, Siluridie. (Lat. silurus, a sheathfish.) The name of the family of fishes of which the genus Silurus is the type, and which includes the electric silurus (Mal apter urus electric us). 'I'hey are chiefly distinguished by the want of true scales, having merely a naked skin, or large o eous plates. A strong o eous spine forms the first 'ray of the dorsal and pectoral fins, except in the genus Malapterurtis. SILVA'NUS. A rural Italian deity; so called from Lat. sylva, a wood. He also presided over boundaries. SI'LVER. (Germ.silber.) A white, malleable, ductile, and tenacious metal, of a brilliant lustre when polished, and soft when pure. Its specific gravity is 105. It is not altered by air or moisture, but is blackened or tarnished by sulphuretted hydrogen. When melted in open ve els it has the curious property of absorbing oxygen, which it gives out when it congeals. This is the cause of the appearance of granular crystallization which silver a umes when hastily cooled: a smaWper-centage of copper entirely prevents the effect. The only pure acids which act upon silver are the nitric and sulphuric. The nitric acid di olves silver without the aid of heat, nitrous gas is evolved, and a dense colourle solution obtained, from which tabular crystals of nitrate of silver may be procured by evaporation. These crystals are anhydrous, and consist of 118 oxide of silver and 54 nitric acid, the equivalent of silver being 110. When melted, and cast into sticks or quills, they form the lunar caustic of the surgeons. Any gold which the silver might have contained, being insoluble in nitric acid, remains in the form of a black powder, and this simple proce enables us readily to separate those metals. Silver is not attacked by cold sulphuric acid; but when granulated silver is heated in concentrated sulphuric acid, one portion of the acid is decomposed and imparts oxygen to the silver; sulphurous acid is evolved, and the oxide of silver di olves in the residuary acid, forming a sulphate of silver. It is a diflScultly soluble salt, forming anhydrous acicular crystals. In this case, the gold also remains undi olved; and as sulphuric is much cheaper than nitric acid, it is used for the separation of those metals upon the large scale. The solutions both of the nitrate and sulphate of silver are decomposed by the immersion of several of the other metals. Copper is generally used for the purpose; which, when immersed in the solution of silver, causes its separation in the form of a grey metallic powder, which is sometimes technically called water silver. Chlorine and all the soluble chlorides, when added to solutions of silver, occasion a white curdy precipitate, which is distinguished by the rapidity with which it blackens by exposure to light. The substance thus formed is a chloride of silver, composed of 110 silver -f36 chlorine, the equivalent of chloride of silver being 146. It is not decomposed by heat alone; but when carefully melted it concretes into a horny substance, formerly called j luna cornea. Chloride of silver may be easily decomposed! either by mixing it in a moist state with zmc filings, or by fusing it with carbonate of soda or potash: in either case metallic silver is obtained. The insolubility of chlo  Page 1132