Silistria (Turk. Dristra), a fortified town of European Turkey, in Bulgaria, on the right bank of the Danube, 57 m. N. N. E. of Shumla and 230 m. N. N. W. of Constantinople; pop. with the garrison about 20,000. The river is here more than 1,200 ft. wide, and studded with numerous islands between the town and the Wallachian shore. There are several mosques, a large Greek church and convent, capacious barracks, public baths, and a custom house with magazines for storing grain and flour. It has no important manufactures, and the chief trade is in wood and cattle. It is a very ancient place, and near the city are remains of fortifications erected during the Byzantine empire. In 971 the emperor John Zimisces here routed the Russians under Sviatoslav. It was besieged by the Russians in 1773, and again in 1779, when they suffered a severe loss. It capitulated to them in 1810. In 1828 they besieged it for several months, and were obliged to retire; but in 1829 it was reduced by them, and held for some years as a pledge for the payment of an indemnity by the Porte, but was eventually returned. In 1849-53 the fortifications were greatly strengthened by the addition of 12 detached forts, of which that on the hill commanding the town is one of the best military works of the time.

In May, 1854, it was invested by Gortchakoff, and afterward by Paskevitch; but after bombarding it for 39 days the Russians retreated with a loss of about 12,000 men and most of their armament. During the siege the town was laid in ruins by the Russian batteries and mines. SILK, a fibre obtained chiefly from the cocoons of the caterpillar of the mulberry tree moth (bombyx mori). The fibre produced by other species of the genus bombyx and by other genera of the same family is inferior to that of B. mori. For an account of these silk-producing insects, see Silkworm. The spider's thread resembles silk in character, but the rearing of spiders is so difficult, and the produce of each individual so small, that all attempts to convert the fibre into textile fabrics have been abandoned. The byssus of the pinna nobilis, a shell fish inhabiting the Mediterranean, consists of long, silken filaments, which have sometimes been woven into fabrics, but rather for curiosity than for use. The manufacture of silk doubtless originated in China. It is asserted by Chinese historians that the wife of the emperor Hvvang-ti (about 2600 B. C.) was the first who unwound the silkworm's cocoon.

As early as the time of Aristotle silken fabrics were woven in the island of Cos, but the fibre there employed appears to have been imported from the country of the Seres (Chinese). Later the product of the Coan looms was famous throughout the Roman empire as Goa vestis, a transparent gauze. The silkworm was unknown to Europe prior to the reign of Justinian (A. D. 527-5G5), when some "grains" or eggs of the insect were brought to Constantinople by two Persian monks, the introduction of the white mulberry following soon after. The silk manufacture made rapid progress, its chief centres being Thebes, Corinth, and Argos. In 1147 many inhabitants of Grecian cities who were skilled in this art were taken prisoners by Roger, king of Sicily, and carried to Palermo. The silk industry soon spread into Italy, and Venice, Milan, Florence, and Lucca were distinguished for the excellence of their fabrics. The Moors at an early period introduced the manufacture into Spain, and a flourishing silk trade was already established at Granada when that city was captured by Ferdinand the Catholic. Louis XI. of France in 1480, and Francis I. while the French occupied Milan in 1521, introduced workmen from there for the purpose of establishing the production of silk in France; but the attempts were not successful till 1564, when a gardener at Nimes had cultivated the white mulberry trees and prepared suitable food for the worms.

The silk manufacture had a rapid development in the south of France, and England began to import thence costly fabrics, such as she had previously imported from Italy and China. The manufacture of silk goods made great progress in England during the reign of James I., and it is said that in 1666 the trade had become so important as to give employment to 40,000 persons. In 1685 a large body of silk weavers, driven from France by the revocation of the edict of Nantes, took refuge in England and settled in Spitalfields, London, where they established several new branches of the art. In 1783 the value of the silk products was rated at £3,350,000. James I. early sought to establish silkworm culture in the American colonies. He himself forwarded eggs to Virginia, and high rewards were offered with the hope of placing the culture upon a permanent footing. But it was all in vain; tobacco superseded silk. In Louisiana the cultivation of silk was introduced in 1718 by the " Company of the West." Government grants were made to the settlers in Georgia, to encourage the cultivation of the mulberry tree. Artisans were sent to that colony in 1732 from different parts of Europe to direct the management of the worms and winding of the silk, and trees, seed, and silkworm eggs were abundantly furnished.

In 1734 the first export of raw silk, amounting to 8 lbs., was made to England. More was sent the next year, and being manufactured into organzine by Sir Thomas Lombe, it was much admired. At the German settlement of Ebenezer, on the Savannah river, the production in 1749 had amounted to over 1,000 lbs. of cocoons, and the silk was so well reeled that it commanded in London the highest prices. In 1751 the trustees of the Ebenezer settlement erected in Savannah a public filature or silk house, to instruct in the management of private filatures. At the end of 1754 the exports of raw silk for the four preceding years amounted in value to $8,880, and for the next 18 years the annual exports averaged 546 lbs. The cocoons delivered at the filature in 1757 were 1,050 lbs.; in 1760, 15,000 lbs.; and in the next eight years they amounted altogether to nearly 100,000 lbs. But when parliament in 1766 reduced the price of cocoons from 3s. (one half of which had been in the way of bounty) to Is. 6d., the production rapidly declined from 20,000 lbs. of cocoons in 1766 to 290 lbs. in 1770. The business was entirely broken up by the revolutionary war.

In South Carolina silk growing was practised before the revolution by the Swiss settlers at Perrysburg, and also by the French, who wrought it up with wool into fabrics. In 1765, 630 lbs. of cocoons were raised upon a plantation in St. Thomas parish; but though some progress continued to be made in the business, it was at last brought to an end by the same causes that broke it up in Georgia. In Connecticut the culture of silk was also undertaken at an early period, and was encouraged by the home government as in the other colonies. Dr. Aspin-wall succeeded in establishing the business in Mansfield, Conn., where it is still carried on, and before the revolutionary war it was already in a very promising condition. In 1789 about 200 lbs. of raw silk, worth $5 a pound, were made at Mansfield; it was mostly manufactured into stockings, handkerchiefs, ribbons, buttons, and sewing silk worth $1 an ounce. In 1790 about 50 families in New Haven were engaged in the business, and in Norfolk about 30 families raised and spun 1,200 "run of silk." In 1839 the product of Mansfield and its vicinity is reported to have been about five tons of raw silk. In Massachusetts attention was also directed to the silk culture in the latter part of the last century.

The town of Ipswich was noted in the manufacture of silk and thread lace. A filature was opened in 1770 at Philadelphia, and 1771 from June to the middle of August it received 2,300 lbs. of cocoons. In some of the interior towns of Pennsylvania, as "Washington in the S. W. part, silk is still produced to a moderate extent, and not only converted into sewing silk, but also woven. In Ohio, the E. parts of Kentucky and Tennessee, and 1ST. Georgia, the production has proved well adapted to the soil and climate, and many have anticipated for it a great success in this portion of the country. There seem in fact to be no natural obstacles to the prosecution of the business over all the middle and southern portion of the United States. Several species of mulberry, quite as well adapted for feeding the worms in the early stages of their growth as the white mulberry, grow wild from Pennsylvania southward, and are easily cultivated in other districts. The foreign species of the tree have also been introduced, and are now almost as well known as the native sorts.

The total product of silk raised in the United States in 1840 was reported at 61,552 lbs., worth about $250,000. In 1844, according to the report of the commissioners of the census, it was 396,790 lbs., worth $1,400,000; but in 1850 it was only 14,763 lbs. The United States census of 1870 gives no statistics of native silk culture; neither is there any mention of American silk in the "Report of the Silk Association of America" for 1875. The growth and manufacture of silk have been successfully attempted in California. Just before the breaking out of the Franco-German war, French cooperation had been secured for the establishment of a silk colony in San Bernardino co.; but the project failed, owing to the disastrous termination of that conflict. There was in San Jose in 1875 one cocoonery with about 1,000,000 silkworms, and a silk manufacturing company has been organized in San Francisco. In the same year Sonoma co. had an association for the promotion of silkworm culture. - Silk Manufacture. The cocoons consist of the sheath of loose filaments attached to the twigs that support the whole, and beneath this the external coat of soft flossy silk, within which is the compact oval ball, or cocoon proper.

The thread, as laid by the worm in successive coats in his constantly diminishing tenement, is not wound regularly around the inside of the hollow ball, but is passed back and forth in one place after another in such manner that many yards may be wound off without turning over the ball. It is produced through two orifices in the nose of the worm, and the two fibres on issuing forth are secured together by the glutinous matter which accompanies them and forms nearly one quarter of their weight. The average size of each one of the primary fibres is about 1/2000 of an inch. Raw silk consists of any number of the double filaments slightly twisted and agglutinated together to form one thread, called single. This is commonly of a golden yellow color, of specific gravity 1.3, and is the strongest of all fibres used for weaving, threads made of it being three times stronger than those of the same size made of flax, and twice as strong as those of hemp. Some of the best cocoons are kept for breeding; the remainder are classified, each sort being worked by itself.

Before the chrysalis matures and the moth can begin to eat his way out, the cocoons are exposed to a moderate degree of heat, either in an oven, or in a steam bath, or in water heated to about 200° F. The floss covering being opened at one end, the cocoon is slipped out, and is then ready to be unwound. The cocoons are placed about five together in each one of four compartments in a sort of trough or basin holding hot water, which is kept at the necessary temperature by a steam pipe. The gummy matters are softened by the water, and the fibre is thus released. The ends are caught up by a little sort of broom with which the cocoons are stirred, and those from each compartment being brought together are passed through an eyelet, which strips off a portion of the gum, and still more is rubbed off by causing the threads formed by each bundle of fibres to cross and rub against each other, as they are conducted diagonally through a succession of eyelets toward the reel, just previous to reaching which all are united in one thread. The reel is set at some distance from the trough, to allow the gum to harden, and prevent the threads from sticking together; and it has a slight lateral motion, so that the threads are laid in spirals, and do not come in contact while fresh from the bath.

When a' thread breaks, or a cocoon gives out, a fresh cocoon is substituted; and as the inner fibres are always much finer than the outer, new cocoons are added before the first lot have been unwound. These finer filaments, as also the immediate envelope of the chrysalis, constitute with the floss silk what is known as waste. The raw silk taken off from the reels is in China made up into bundles, called books, for exportation, and elsewhere the hanks are simply twisted so as to hold snugly together. They are then ready for the factory of the silk throwsters, where are conducted the operations connected with the throwing, a term variously used to express the putting a twist into fibres. For bandanna handkerchiefs the only preparation of the silk is winding the hanks and cleaning; bleaching is added for silk intended for gauze and similar fabrics. Winding, cleaning, and throwing prepare it, under the name of thrown singles, for ribbons and common silks. If simply doubled before throwing, it is known as tram, and is used for the woof or shoot of gros de Naples, velvets, and flowered silks. The twisting of each strand before doubling, as well as afterward, converts it into organzine, a strong thread suitable for warp.

The winding is done from light six-sided reels called swifts, upon which the hanks, first washed in soap and water, are extended, and rows of which are set upon long shafts in an iron frame and connected each with its own bobbin, upon the top of the frame. The revolution of the latter carries around the reel beneath, and the movement is properly checked and regulated by appliances to the reel. The next process is that of cleaning the threads, which is effected upon the cleaning, drawing, or picking machine. The full bobbins are set horizontally upon plain spindles, from which each thread is conducted over an iron or glass guide rod, thence through an adjustable opening between two upright iron blades of an instrument called the cleaner, and then to the empty bobbins, which by their revolution wind it off from the full ones. Knots and other irregularities are stopped by the cleaner, and if not brushed off they stop the movement of the bobbin until they are removed by hand. The spinning or rather twisting process is conducted by means of machines similar to those used for the same purpose in cotton spinning. Doubling is the process of bringing two or more of the twisted threads into one and winding this.

The bobbins of doubled thread are next twisted at the spinning frames, which completes the preparation of silk thread whether for sewing or weaving purposes. The American machines for doubling and twisting are much superior to those used in England, but for winding the same are employed in both countries. The thread is colored by dyeing after the gum has been removed from it by boiling for three or four hours in soap and water. It loses about one quarter its weight by this operation, but recovers nearly half the loss in the dye stuff it absorbs. - Waste silk is prepared for spinning by first hackling in the same manner as flax is hackled, and with the same sort of hand instrument. This is followed by machine hackling upon the filling engine, which more effectually combs out the filaments and removes the impurities. The sliver of parallel fibres is then chopped into lengths of about 1¼., which after scutching, as in the treatment of cotton, are converted into a sort of fine down. This is put into bags and boiled, first with soap and water for an hour and a half, and afterward with pure water. It is then powerfully squeezed under a Bramah press, dried by artificial heat, and again scutched.

The succeeding operations of carding, drawing, and roving by the fly frames, and spinning by the spinning mill and throstle frames, are similar to those practised in the manufacture of cotton yarns. The product is adapted for the manufacture of shawls, bandanna handkerchiefs, and similar fabrics. - In the year ending Dec. 31, 1874, there were in the United States 180 silk manufactories, employing 141,479 operatives of both sexes, distributed as follows: New Jersey 42, with 5,414 operatives; New York 70, with 3,378; Connecticut 21, with 2,651; Pennsylvania 23, with 1,541; Massachusetts 11, with 1,249; California 3, with 100; Ohio 3, with 40; Illinois 2, with 35; New Hampshire, Maryland, Vermont,- Missouri, and Kansas, each 1. The total capital invested was $14,708,184; total value of production, $20,082,482. Of this sum, thrown and spun silks amounted to $3,863,325; sewing silks and machine twist, $5,766,684; broad goods and ribbons, $6,154,-313; laces, braids, and trimmings, $4,298,196. The importations of silk into the United States for the year ending June 30, 1875, were as follows: raw silk, 1,101,681 lbs., costing at the foreign port of shipment, $4,504,306; sewing silk, $30,889; silk, satins, crapes, pongees, plushes, ribbons, etc, $19,226,672; gloves and hosiery, $71,053; mixed goods, $3,482,369; total, $27,314,787. There were imported besides 398,012 lbs. of cocoons.

The silk crop of Europe in the year 1874-'5 was 9,000,000 lbs., of which Italy supplied 6,300,000, France 1,600,000, and Spain about 310,000. The import from Asia amounted to 11,500,000 lbs.