SILK is a fibrous substance produced by many insects, principally in the form of a cocoon or covering within which the creatures are enclosed and protected during the period of their principal transformations. The webs and nests, &c, formed by spiders are also of silk. But the fibres used for manufacturing purposes are exclusively produced by the mulberry silk-moth of China, Bombyx mori, and a few other moths closely allied to that insect (see vol. iv. p. 596). Among the Chinese the name of the silk-worm is " si," Corean "soi"; to the ancient Greeks it became known as _____, the nation whence it came was to them _____, and the fibre itself _____, whence the Latin sericum, the French soie, the German Seide, and the English silk.
The silk industry originated in China; and according to native records it has existed there from a very remote period. The empress Se-ling-she, wife of a famous emperor, Hwang-te (2640 B.C.), encouraged the cultivation of the mulberry tree, the rearing of the worms, and the reeling of silk. This empress is said to have devoted herself personally to the care of silkworms, and she is by the Chinese credited with the invention of the loom. A voluminous ancient literature testifies not only to the antiquity but also to the importance of Chinese sericulture, and to the care and attention bestowed on it by royal and noble families. The Chinese guarded the secrets of their valuable art with vigilant jealousy; and there is no doubt that many centuries passed before the culture spread beyond the country of its origin. Through Corea a knowledge of the silkworm and its produce reached Japan, but not before the early part of the 3d century. One of the most ancient books of Japanese history, the lYihongi, states that towards 300 A.D. some Coreans were sent from Japan to China to engage competent people to teach the arts of weaving and preparing silk goods. They brought with them four Chinese girls, who instructed the court and the people in the art of plain and figured weaving; and to the honour of these pioneer silk weavers a temple was erected in the province of Setsu. Great efforts were made to encourage the industry, which from that period grew into one of national importance. At a period probably little later a knowledge of the working of silk travelled west-ward, and the cultivation of the silkworm was established in India. According to a tradition the eggs of the insect and the seed of the mulberry tree were carried to India by a Chinese princess concealed in the lining of her headdress. The fact that sericulture was in India first established in the valley of the Brahmaputra and in the tract lying between that river and the Ganges renders it probable that it was introduced overland from the Chinese empire. From the Ganges valley the silkworm was slowly carried westward and spread in Khotan, Persia, and the states of Central Asia.
Most critics recognize in the obscure word dmeshek, Amos iii. 12, a name of silk corresponding to the Arabic dimaks, late Greek ______, English damask, and also follow the ancients in understanding meshi, Ezek. xvi. 10, 13, of "silken gauze." But the first notice of the silkworm in class, the preservation of his Western literature occurs in Aristotle, Hist. Anim., v. 19 (17), 11 (6), where he speaks of "a great worm which has horns and so differs from others. At its first metamorphosis it produces a caterpillar, then a bombylius, and lastly a chrysalis,all these changes taking place within six months. From this animal women separate and reel off the cocoons and afterwards spin them. It is said that this was first spun in the island of Cos by Pamphile, daughter of Plates. Aristotle's vague knowledge of the worm may have been derived from informa-tion acquired by the Greeks with Alexander the Great; but long before this time raw silk must have begun to be imported at Cos, where it was woven into a gauzy tissue, the famous Coa vestis, which revealed rather than clothed the form.
Towards the beginning of the Christian era raw silk began to form an important and costly item among the prized products of the East which came to Rome. Allusions to silk and its source became common in classical literature; but, although these references show familiarity with the material, they are singularly vague and inaccurate as to its source; even Pliny knew nothing more about the silkworm than could be learned from Aristotle's description. The silken textures which at first found their way to Rome were necessarily of enormous cost, and their use by men was deemed a piece of effeminate luxury. From an anecdote of Aurelian, who neither used silk himself nor would allow his wife to possess a single silken garment, we learn that silk was worth its weight in gold.
Notwithstanding its price and the restraints otherwise put on the use of silk the trade grew. Under Justinian a monopoly of the trade and manufacture was reserved to the emperor, and looms, worked by women, were set up within the imperial palace at Constantinople. Justinian also endeavoured, through the Christian prince of Abyssinia, to divert the trade from the Persian route along which silk was then brought into the east of Europe. In this he failed, but two Persian monks who had long resided in China, and there learned the whole art and mystery of silkworm rearing, arrived at Constantinople and imparted their knowledge to the emperor. By him they were induced to return to China and attempt to bring to Europe the material necessary for the cultivation of silk, which they effected by concealing the eggs of the silkworm in a hollow cane. From the precious contents of that bamboo tube, brought to Constantinople about the year 550, were produced all the races and varieties of silkworm which stocked the Western world, and which gave trade, prosperity, and untold wealth to great communities for more than twelve hundred years. The necessity for again going to the East for a supply of silkworm eggs has only arisen in our own day.
Under the care of the Greeks the silkworm took kindly to its Western home and flourished, and the silken textures of Byzantium became famous. At a later period the conquering Saracens obtained a mastery over the trade, and by them it was spread both east and west, the textures becoming meantime impressed with the patterns and colours peculiar to that people. They established the trade in the thriving towns of Asia Minor, and they planted it as far west as Sicily, as Sicilian silks of the 12th century with Saracenic patterns still testify. Ordericus Vitalis, who died in the first half of the 12th century, mentions that the bishop of St Evroul, in Normandy, brought with him from Apulia in southern Italy several large pieces of silk, out of the finest of which four copes were made for his cathedral chanters. The cultivation and manufacture spread northwards to Florence, Milan, Genoa, and Veniceall towns which became famous for silken textures in mediceval times. In 1480 silk weaving was begun under Louis XI. at Tours, and in 1520 Francis I. brought from Milan silkworm eggs, which were reared in the Rhone valley. About the beginning of the 17th century Olivier de Serres and Laffémas, somewhat against the will of Sully, obtained royal edicts favouring the growth of mulberry plantations and the cultivation of silk; but it cannot be said that these industries were firmly established till Colbert encouraged the planting of the mulberry by premiums, and otherwise stimulated local efforts.
Into England silk manufacture was introduced during the reign of Henry VI.; but the first serious impulse to manufactures of that class was due to the immigration in 1585 of a large body of skilled Flemish weavers who fled from the Low Countries in consequence of the struggle with Spain then devastating their land. Precisely one hundred years later religious troubles again gave the second and most effective impetus to the silk-trade of England, when the revocation of the edict of Nantes sent simultaneously to Switzerland, Germany, and England a vast body of the most skilled artisans of France, who planted in these countries silk-weaving colonies which are to this day the principal rivals of the French manufacturers. The bulk of the French Protestant weavers settled at Spitalfields, London,an incorporation of silk throwsters having been there formed in 1629. James I. used many efforts to encourage the planting of the mulberry and the rearing of silkworms both at home and in the colonies. In 1825 a public company was formed and incorporated under the name of the British, Irish, and Colonial Silk Company, with a capital of £1,000,000, principally with the view of introducing sericulture into Ireland, but it was a complete failure, and the rearing of the silkworm cannot be said ever to have become a branch of British industry.
In 1522 Cortes appointed officials to introduce sericulture into New Spain (Mexico), and mulberry trees were then planted and eggs were brought from Spain. The Mexican adventure is mentioned by Acosta, but all trace of the culture had died out before the end of the century. In 1609 James I. attempted to reinstate the silkworm on the American continent, but his first effort failed through shipwreck. An effort made in 1619 obtained greater success, and, the materials being present, the "Virginian settlers were strongly urged to devote attention to the profitable industry of silk cultivation. Sericulture was enjoined under penalties by statute; it was encouraged by bounties and rewards; and its prosecution was stimulated by learned essays and rhapsodical rhymes, of which this is a sample:
"Where Wormes and Food doe naturally abound A gallant Silken Trade must there be found. Virginia excels the World in both Envie nor malice can gaine say this troth!"
In the prospectus of Law's great Compagnie des Indes Occidentales the cultivation of silk occupies a place among the glowing attractions which allured so many to disaster. Onward till the period of the War of Independence bounties and other rewards for the rearing of worms and silk filature continued to be offered; and just when the war broke out Benjamin Franklin and others were engaged in nursing a filature into healthy life at Philadelphia. With the resumption of peaceful enterprise, the stimulus of bounties was again appliedfirst by Connecticut in 1783 ; and such efforts have been continued sporadically down almost to the present day. Bounties were last offered by the State of California in 1865-66, but the State law was soon repealed, and an attempt to obtain State encouragement again in 1872 was defeated. About 1838 a specu-lative mania for the cultivation of silk devehyped itself with remarkable severity in the United States. It was caused principally through the representations of Samuel Whitmarsh as to the capabilities of the South Sea Islands mulberry (Morus multicaulis) for feeding silkworms; and so intense was the excitement that plants and crops of all kinds were displaced to make room for plantations of midticaulis. In Pennsylvania as much as §300,000 changed hands for plants in one week, and frequently the young trees were sold two and three times over within a few days at ever-advancing prices. Plants of a single year's growth reached the ridiculous price of $1 each at the height of the fever, which, however, did not last long, for in 1839 the speculation collapsed; the famous Morus multicaulis was found to be no golden tree, and the costly plantations were uprooted.
The most singular feature in connexion with the history of silk is the persistent efforts which have been made by monarchs and other potentates to stimulate sericulture within their dominions, efforts which continue to this day in British colonies, India, and America. These endeavours to stimulate by artificial means have in scarcely any instance resulted in permanent success. In truth raw silk can only be profitably brought to the market where there is abundant and very cheap labour,the fact that China, Japan, Bengal, Piedmont, and the Levant are the principal producing localities making that plain.
The mulberry-feeding moth, Bombyx mori, which is the principal source of silk, belongs to the Bombycidae, a family of Lepidoptera in which are embraced some of the largest and most handsome moths (see vol. iv. p 596). B. mori is itself an inconspicuous moth (figs. 1 and 2) of an ashy white colour, with a body in the case of the male not half an inch in length, the female being a little longer and stouter. Its wings are short and weak; the fore pair are falcate, and the hind pair do not reach to the end of the body. The larva (fig. 3) is hair-less, of an ashy grey or cream colour, attains to a length of from 3 to 3J inches, and is slender in comparison with many of its allies. The second thoracic ring is humped, and there is a spine-like horn or protuberance at the tail. The common silkworm produces as a rule only one generation during the year; but there are races in cultivation which are bivoltine, or two-generationed, and some are multi-voltine. Its natural food is the leaves of mulberry trees. The silk glands or vessels consist of two long thick-walled sacs running along the sides of the body, which open by a common orificethe spinneret or seripositoron the under lip of the larva. Fig. 4 represents the head (a) and feet (b, b) of the common silkworm, while c is a dia-grammatic view of the silk glands. As the larva ap-proaches maturity these vessels become gorged with a clear viscous fluid, which, upon being exposed to the air
immediately hardens to a solid mass. Advantage is taken
FIG. 3.Larva of Bombyx mori.
of this peculiarity to prepare from fully-developed larvae silkworm gut used for casting lines in rod-fishing, and for numerous other purposes where lightness, tenacity, flexibility, and strength are essential. The larvae are killed and hardened by steeping some hours in strong acetic acid; the silk glands are then separated from the bodies, and the viscous fluid drawn out to the condition of a fine uniform line, which is stretched between pins at the extremity of a board. The board is then exposed to the sunlight till the lines dry and harden into the condition of gut. The preparation of gut is, however, merely an unimportant collateral manufacture. When the larva is fully mature, and ready to change into the pupa condition, it proceeds to spin its cocoon, in which operation it ejects from both glands simultaneously a line or thread about 4000 yards in length, moving its head round in regular order continuously for three days or thereby. The thread so ejected forms the silk of com-merce, which as wound in the cocoon consists of two filamentsone from each glandlaid side by side and agglutinated into one fibre (Fr. have) by their own adhesive constituents. Under the microscope, therefore, cocoon silk presents the appearance (fig. 5) of a somewhat flattened com-bination of two filaments placed side by side, being on an average from -033 to -036 mm. broad by -020 to -025 mm. in thickness. The cocoons are white or yellow in colour, oviform in shape, with often a constriction in the middle (fig. 6). According to race, &c, they vary con-
-Cocoon of Bombyx morì.
siderably in size and weight, but on an average they measure from an inch to an inch and a half in length, and from half an inch to an inch in diameter. They form hard, firm, and compact shells with some M straggling flossy filaments on the exterior, 4B and the interior layers are so closely and densely agglutinated as to constitute a parchment-like mass which resists all attempts at unwinding. The whole cocoon > . | 7| with its enclosed pupa weighs from 15 grains for the smaller races to about 50 grains for the breeds which spin large cocoons. From two to three weeks after the completion of the cocoon the enclosed insect is ready to escape; it moistens one
end of its self-made prison, thereby enabling itself to push aside the fibres and make an opening by which the perfect moth comes forth. The sexes almost immediately couple; the female in from four to six days lays her eggs, numbering 500 and upwards ; and, with that the life cycle of the moth being complete, both sexes soon die.
The art of sericulture concerns itself with the rearing of silkworms under artificial or domesticated conditions, their feeding, the formation of cocoons, the securing of these before they are injured and pierced by the moths, and the maturing of a sufficient number of moths to supply eggs for the cultivation of the following year. The first essential is a stock of mulberry trees adequate to feed the worms in their larval stage. The leaves preferred in Europe are those of the white-fruited mulberry, Morus alba, but there are numerous other species which appear to be equally suitable. The soil in which the mulberry grows, and the age and condition of the trees, are important factors in the success of silkworm cultivation ; and it has been too often proved that the mulberry will grow in situations where, from the nature of the leaf the trees put forth and from other circumstances, silkworms cannot be profitably reared. An elevated position with dry friable well-drained soil produces the best quality of leaves. Throughout the East the species of mulberry cultivated are numerous, but, as these trees have been grown for special purposes at least for three thousand years, they show the complex variations peculiar to most cultivated plants.
The eggs of the silkworm, called graine, are hatched out by artificial heat at the period when the mulberry leaves are ready for the feeding of the larvae. These eggs are very minuteabout one hundred weighing a grain; and a vast number of hatched worms may at first be kept in a small space; but the rapid growth and voracious appetite of the caterpillars demand quickly increasing and ample space. Pieces of paper punctured with small holes are placed over the trays in which the hatching goes on ; and the worms, immediately they burst their shell, creep through these openings to the light, and thereby scrape off any fragments of shell which, adhering to their skin, would kill them by constriction. The rearing-house in which the worms are fed (Fr. magnanerie) must be a spacious, well-lighted, and well-ventilated apartment, in which scrupulous cleanliness and sweetness of air are essential, and in which the temperature may to a certain extent be under control. The worms are more hardy than is commonly supposed, and endure variations of temperature from 62° to 78° F. without any injury; but higher temperature is very detrimental. The lower the temperature at which the worms are maintained the slower is their growth and development; but their health and vigour are increased, and the cocoon they spin is proportionately bigger. The worms increase in size with astonishing rapidity, and no less remarkable is their growing voracity. Certain races moult or cast their skin three times during their larval existence, but for the most part the silkworm moults four timesabout the sixth, tenth, fifteenth, and twenty-third days after hatching. As these moulting periods approach, the worms lose their appetite and cease eating, and at each period of change they are left undisturbed and free from noise. The worms from 1 oz. of grainenumbering, say, 40,000consume in their first stage about 6 lb of picked leaf, in the second 18 lb, in the third 60 lb, fourth 180 lb, and in their final stage 1098 lb, in all 1362 lb of mulberry leaf; but from that is to be deducted about 590 lb of unconsumed fragments removed in the litter, giving of leaf really consumed 772 lb. An ounce of graine so treated may yield from 80 to 120 lb of cocoons, 85 per cent, of which consists of the weight of chrysalides and 15 per cent, of pure cocoon. The growth of the worms during their larval stage is thus stated by Count Dandolo :
== TABLE ==
When the caterpillars are mature and ready to undergo their transformation into the pupa condition, they cease eating for some time and then begin to ascend the brushwood branches or echelletes provided for them, in which they set about the spinning of their cocoons. Crowding of positions must now be guarded against, to prevent the spinning of double cocoons (doubions) by two worms spinning together and so interlacing their threads that they cannot be reeled. The insects complete their cocoons in from three to four days, and in two or three days there-after the cocoons are collected, and the pupa killed to prevent its further progress and the bursting of the shell by the fully developed moth. Such cocoons as are selected for the production of graine, on the other hand, are col-lected, freed from the external floss, and preserved at a temperature of from 66° to 72° Fahr., and after a lapse of from eleven to fifteen days the moths begin to make their appearance. The coupling which immediately takes place demands careful attention ; the males are afterwards thrown away, and the impregnated females placed in a darkened apartment till they deposit their eggs.
Diseases.That the silkworm is subject to many and serious diseases is only to be expected of a creature which for upwards of 4000 years has been propagated under purely artificial conditions, and these most frequently of a very insanitary nature, and where, not the healthy life of the insect, but the amount of silk it could be made to yield was the object of the cultivator. Among the most fatal and disastrous of these diseases with which the cultivator had long to grapple was "muscardine," a malady due to the development of a fungus, Sotrytis bassiana, in the body of the caterpillar. The disease is peculiarly contagious and infectious, owing to the development of the fungus through the skin, whence spores are freed, which, coming in contact with healthy caterpillars, fasten on them and germinate inwards, giving off corpuscles within the body of the insect. Muscardine, however, has not been epidemic for many years. But about the year 1853 anxious attention began to be given in France to the ravages of a disease among silkworms, which from its alarming progress threatened to issue in national disaster. This disease, which at a later period became known as "pebrine," a name given to it by M. de Quatrefages, one of its many in-vestigators, had first been noticed in France at Cavaillon in the valley of the Durance near Avignon. Pebrine manifests itself by dark spots in the skin of the larvae ; the eggs do not hatch out, or hatch imperfectly; the worms are weak, stunted, and unequal in growth, languid in movement, fastidious in feeding ; many perish before coming to maturity ; if they spin a cocoon it is soft and loose, and moths when developed are feeble and inactive. When sufficient vitality remains to produce a second generation it shows in increased intensity the feebleness of the preceding. The disease is thus hereditary, but in addition it is virulently infectious and contagious. From 1850 onwards French cultivators were com-pelled, in order to keep up their silk supply, to import graine from uninfected districts. The area of infection increased rapidly, and with that the demand for healthy graine correspondingly expanded, while the supply had to be drawn from increasingly remote and contracted regions. Partly supported by imported eggs, the production of silk in France was maintained, and in 1853 reached its maximum of 26,000,000 kilos of cocoons, valued at 117,000,000 francs. From that period, notwithstanding the importation at great cost of foreign graine, reaching in some years to 60,000 kilos, the production of silk fell off with startling rapidity: in 1856 it was not more than 7,500,000 kilos of cocoons ; in 1861 and 1862 it fell as low as 5,800,000 kilos ; and in 1865 it touched its lowest weight of about 4,000,000 kilos. In 1867 De Quatrefages estimated the loss suffered by France in the 13 years following 1853, from decreased production of silk and price paid to foreign cultivators for graine, to be not less than one milliard of francs. In the case of Italy, where the disease showed itself later but even more disastrously, affecting a much more extended industry, the loss in 10 years De Quatrefages stated at two milliards. A loss of £120,000,000 sterling within 13 years, falling on a limited area, and on one class within these two countries, constituted indeed a calamity on a national scale, calling for national effort to contend with its devastating action. The malady, moreover, spread east-ward with alarming rapidity, and, although it was found to be less disastrous and fatal in Oriental countries than in Europe, the sources of healthy graine became fewer and fewer, till only Japan was left as an uninfected source of European graine supply.
A scourge which so seriously menaced the very existence of the silkworm in the world necessarily attracted a great amount of attention. The disease was studied by the most eminent men of science ; reports and suggestions innumerable were made, and a whole pharmacopoeia of remedies proposed. So early as 1849 M. Guerin Meneville observed in the blood of diseased silkworms certain vibratory corpuscles, but neither did he nor the Italian Signor Filippi, who studied them later, connect them distinctly with the disease. The corpuscles were first accurately described by Signor Cornalia, whence they are spoken of as the corpuscles of Cornalia. The French Academy charged MM. de Quatrefages, Decaisne, and Peligot with the study of the disease, and these learned men issued two elaborate reportsEtudes sur les Maladies Actuelles des Vers à Soie, 1859, and Nouvelles Recherches sur les Maladies Actuelles des Vers à Soie, 1860; but the suggestions they were able to offer had not the effect of stopping the march of the disease. In 1865 M. Pasteur undertook a Government commission for the investigation of the malady. Attention had been previously directed to the corpuscles of Cornalia, and it had been found, not only that they occurred in the blood, but that they gorged the whole tissues of the insect, and their presence in the eggs themselves could be microscopically demonstrated. Pasteur set himself to elucidate the life-history of these corpuscles, and he soon established (1) that the corpuscles are the special characteristic of the disease, and that these invariably manifest themselves, if not in earlier stages, then in the mature moths; (2) that the corpuscles are parasites, and not only the sign but the cause of the disease; and (3) that the disease manifests itself by heredity, by contagion with diseased worms, and by the eating of leaves on which corpuscles are spread. In this connexion he established the very important practical conclusion that worms which contract the disease during their own life-cycle retain sufficient vitality to feed, develop, and spin their cocoon, although the next generation is invariably infected and shows the disease in its most virulent and fatal form. But this fact enabled the cultivator to know with assurance whether the worms on which he bestowed his labour would yield him a harvest of silk. He had only to examine the bodies of the moths yielding his graine: if they were free from disease then a crop was sure; if they were infected the education would assuredly fail. Pasteur brought out the fact that the malady had existed from remote periods and in many unsuspected localities. He found corpuscles in Japanese cocoons and in many specimens which had been pre' served for lengthened periods in public collections. Thus he came to the conclusion that the malady had been inherent in many suc-cessive generations of the silkworm, and that the epidemic condition was only an exaggeration of a normal state brought about by the method of cultivation and production of graine pursued. The cure proposed by Pasteur was simply to take care that the stock wdience graine was obtained should be healthy, and the offspring would then be healthy also. Small educations reared apart from the ordinary magnanerie, for the production of graine alone, were re-commended. At intervals of five days after spinning their cocoons specimens were to be opened and the chrysalides examined micro-scopically for corpuscles. Should none have appeared till towards the period of transformation and escape of the moths, the eggs subsequently hatched out might be depended on to yield a fair crop of silk; should the moths prove perfectly free from corpuscles after depositing their eggs the next generation would certainly live well through the larval stage. For special treatment towards the regeneration of an infected race, the most robust worms were to be selected, and the moths issuing from the cocoons were to be coupled in numbered cells, where the female was to be confined till she deposited her eggs. The bodies of both male and female were to be examined for corpuscles, and the eggs of those found absolutely free from taint were preserved for similar "cellular" treatment in the following year. By this laborious and painstaking method it has been found possible to re-establish a healthy stock of valuable races from previously highly-infected breeds. The rearing of worms in small educations under special supervision has been found to be a most effective means of combating pebrine. In the same way the rearing of worms for graine in the open air, and under as far as possible natural conditions, has proved equally valuable towards the development of a hardy, vigorous, and untainted stock. The open-air education was originally proposed by Dr Chavannes of Lausanne, and largely carried out in the canton of Vaud by M. Roland, who reared his worms on mulberry trees enclosed within "manchons" or cages of wire gauze and canvas. The insects appeared quickly to revert to natural conditions; the moths brought out in open air were strongly marked, lively, and active, and eggs left on the trees stood the severity of the winter well, and hatched out successfully in the following season. M. Roland's experience demonstrated that not cold but heat is the agent which saps the constitution of the silkworm and makes it a ready prey to disease.
Wild Silks.The ravages of pebrine and other diseases had the effect of attracting prominent attention to the numerous other insects, allies of the mulberry silkworm, which spin serviceable cocoons. It had been previously pointed out by Captain Hutton, who devoted great attention to the silk question as it affects the East Indies, that at least six species of Bombyx, differing from B. mori, but also mulberry-feeding, are more or less domesticated in India. These include B. textor, the boro-pooloo of Bengal; a large species having one generation yearly and pro-ducing a soft cocoon ; the Chinese monthly worm, B. sinensis, having several generations, and making a small cocoon ; and the Madrasi worm of Bengal (B. croesi), the Dassee or Desi worm of Bengal (B. fortunatus), and B. arracanensis, the Burmese worm,all of which yield several generations in the year and form reelable cocoons. Besides these there are many other mulberry-feeding Bombycidae in the East, principally belonging to the genera Tlieophila and Ocinara, the cocoons of which have not attracted cultivators. The moths yielding wild silks which have obtained most attention belong to the extensive and handsome family Saturnidae. The most important of the species at the present time is the Chinese tussur or tasar worm, Anthersea opernyi (figs. 7, 8), an oak-feeding species, native of Mongolia, from which is derived the greater part of the so-called tussur silk now imported into Europe. Closely allied to this is the Indian tussur moth (fig. 9) Anthersea mylitta, found
FIG. 8. Cocoon of Anthersea pemyi.
throughout the whole of India feeding on the bher tree, Zizyphus jujuba, and on many other plants. It yields a large compact cocoon (fig. 10) of a silvery grey colour, which Mr Thomas "Wardle of Leek, who has devoted a great amount of attention to the wild-silk ques-tion, has succeeded in reeling. Next in promising qualities is the muga or moonga worm of Assam, Antherma assama, a species to some extent domesticated in its native country. The yama-mai worm of Japan, Antherwa (Samia) yama-mai, an oak-feeder, is a race of considerable importance in Japan, where it was said to be jealously guarded against foreigners. Its eggs were first sent to Europe by M. Duchene du Bellecourt, French consul-general in Japan in 1861 ; but early in March following they hatched out, when no leaves on which the larvae would feed were to be found. In April a single worm got oak-buds, on which it throve, and ultimately spun a cocoon whence a female moth issued, from which M. Guerin Meneville named and described the species. A further supply of eggs was secretly obtained by a Dutch physician M. Pompe van Meedervoort in 1863, and, as it was now known that the worm was an oak-feeder, and would thrive on the leaves of European oaks, great results were anticipatedfrom A the cultivation of the jm yama-mai. These ex-pectations, however,
FIG. 9.Anthersea mylitta (female).
have been disappointed. The moths hatch o"ut at a period when oak leaves are not ready for their feeding, and the silk is by no means'of a quality to compare with that of the common mulberry worm. The mezan-koorie moth of the Assamese, Anthereea mezankooria, yields a valuable cocoon, as does also the Atlas moth, Attacus atlas, which has an omnivorous larva found throughout India, Ceylon, Burmah, China, and Java. The Cynthia moth, Attacus eynthid, is domesticated as a source of silk in certain provinces of China, where . it feeds on the A ilanthus glandulosa. The eria or arrindi moth of Bengal and Assam, Attacus ricini, which feeds on the castor-oil plant, yields seven generations yearly, forming loose flossy orange-red and sometimes white cocoons. The ailanthus silkworm of Europe is a hybrid between A. eynthia and A. ricini, first obtained by Guerin Meneville, and now spread through many silk-growing regions. These are only a few of the moths from which silks of various usefulness can be produced ; but none of these presents qualities, saving perhaps cheapness alone, which can put them in competition with common silk.
Physical and Chemical Relations of Silk.
Common cocoons enclosing chrysalides weigh each from 16 to 50 grains, or say from 300 to 600 of small breeds and from 270 to 300 of large breeds to the lb. One-seventh of this weight is pure cocoon, and of that not more than one-half is obtainable as reeled silk, the remainder consisting of surface floss and of hard gummy husk or "tomb." The total length of double thread or "bave" which the silk-worm winds into its cocoon may amount to 4000 yards; the quantity reelable therefrom rarely exceeds 900 yards, and may range from 330 to 650 yards. It is found that the reelable fibre is as a rule thickest and strongest at the middle portion, tapering down very notably towards each extremity. In 1885 Mr T. Wardle of Leek showed by an elaborate series of measurements that the transverse section of common silk double thread or bave measures on the average ______ in. at the thinnest and from to in. at the thickest part, and in some instances the middle was one-third thicker, stronger, and more elastic than the ends. As a great deal of silk remains on the husk after reeling, it is obvious that the thread last emitted by the silkworms on the inner wall of the cocoons must be of extreme tenuity. The silk of the various species of Antherxa and Attacus is also thicker and stronger at the centre of the reeled portion than towards its extremities; but the diameter is much greater than that of common silk, and the filaments under the microscope (fig. 11) present the appearance of flat bands, the exudation from the two spinnerets being joined at their flat edges. On this account the fibres of tussur silk tend to split up into fine fibrillse under the various preparatory processes in manufactur-ing, and its riband struc-ture is the cause of the glassy lustre peculiar to the woven and finished fibres.
Silk fibre consists essentially of a centre or
FIG. 11.Microscopic appearance of Silk of Chinese Tussur.
core of fibroin, with a covering of sericin or silk albumen, and a little waxy and colouring matter. Fibroin, which is analogous to horn, hair, and like dermal products, constitutes about 66 per cent, of the entire mass, and has a composition represented by the formula C15H23N506. It has the characteristic appearance of pure silk,a brilliant soft white body with a pearly lustre,insoluble in water, alcohol, and ether, but it dissolves freely in concentrated alkaline solutions, mineral acids, strong acetic acid, and in ammoniacal solution of oxide of copper. Sericin, which constitutes the gummy covering (Fr. gres) of the fibre, is a gelatinous body which dissolves readily in warm soapy solutions, and in hot water, in which on cooling it forms a jelly with even as little as 1 per cent, of the substance. It is precipitated from hot solutions by alcohol, falling as a white powder. Its formula is C15H25N508. According to the researches of P. Bolley, the glands of the silkworm contain semi-liquid fibroin alone, and it is on exposure to the air that the surface is acted on by oxygen, transforming the ex-ternal pellicle into the more soluble form of sericin. Silk is highly hygroscopic, taking up as much as 30 per cent, of water without feeling perceptibly damp. It is a most perfect non-conductor of electricity, and in its dry state the fibres frequently get so electrically excited as to seriously interfere with their working, so that it becomes necessary to moisten them with glycerin or soapy solutions. Silk is readily distinguished from wool and other animal fibres by the action of an alkaline solution of oxide of lead, which darkens wool, &c, owing to the sulphur they contain, but does not affect silk, which is free from that body. Again, silk dissolves freely in common nitric acid, which is not the case with wool. From vegetable fibres silk is readily distinguished by the bright yellow colour it takes from a solution of picric acid, which does not adhere to vegetable substances. The rod-like appearance of silk and its absence of markings under the microscope are also easily recognizable features of the fibre.
Here we must distinguish between the reeled silk and the spun or waste silk manufactures. The former embraces a range of operations peculiar to silk, dealing as they do with continuous fibres of great length, whereas in the spun silk industry the raw materials are treated by methods analogous to those followed in the treat-ment of other fibres. It is only floss, injured and un-reelable cocoons, the husks of reeled cocoons, and other waste from reeling, with certain wild silks, which are treated by the spun silk process, and the silk thereby produced loses much of the beauty, strength, and brilliance which are characteristic of the manufactures from reeled silk.
Filature or Reeling.When the cocoons have been gathered the chrysalides they contain are killed either by dry heat or by exposure to steam. All cocoons stained by the premature death of the chrysalides (ehiques), pierced cocoons, double cocoons, and any from other causes rendered unreelable, are put aside for the spun-silk manufacture. Then the uninjured cocoons are by themselves sorted into classes having similar shades of colour, size, and quality of fibre. This assortment is of great consequence for the success of the reeling operations, as uniformity of quality and evenness and regularity of fibre are the most valuable features in raw silk. The object of reeling is to bring together the filaments (have) from two or more (generally four or five, but sometimes up to twenty) cocoons, and to form them into one con-tinuous, uniform, and regular strand, which constitutes the '' raw silk " of commerce. To do this, the natural gum of the cocoons which holds the filaments together must be softened, the ends of the filaments of the required number of cocoons must be caught, and means must be taken to unwind and lay these filaments together, so as to form a single uniform rounded strand of raw silk. As the reeling proceeds the reeler has to give the most careful attention to the thickness of the strand being produced, and to introduce new cocoons in place of any from which the reelable silk has become exhausted. In this way a continuous uniform fibre or strand of raw silk of indefinite length is produced. The apparatus used for these purposes in some localities is of a very primitive kind, and the reeling being uneven and lumpy the silk is of inferior quality and low value. With comparatively simple appliances, on the other hand, a skilled reeler, with trained eye and delicate touch, can produce raw silk of remarkably smooth and even quality. According to the method commonly adopted in North Italy and France the cocoons are for a few minutes immersed in water a little under the boiling point, to which a small quantity of alkali has been added. A girl with a small hand brush of twigs keeps stirring them in the water till the silk softens, and the outer loose fibres (floss) get entangled with the twigs and come olf till the end of the main filament (maitre brin) is found. These ends being secured, the cocoons are transferred to a basin or tray containing water heated to from 75° to 85° Fahr., in which they float while the silk is being reeled off. If the water is too cold the gum does not soften enough and the cocoons rise out of the basin in reeling ; if it is too hot the cocoons collapse and fall to the bottom. The ends of the requisite number of filaments being brought together, they are passed through an eyelet or guide, and similarly another equal set are passed through a corresponding guide. The two sets of filaments are then crossed or twisted around each other several turns as if to make one thread, after which they are separated and passed through separate guides to the reel round which they are separately wound. When a large number of cocoons are to be combined into one strand they may be reeled from the tray in four sets, which are first crossed in pairs, then combined into two, and those two then crossed and after-wards combined into a single strand. The object of crossing (croissage) is to round, smooth, and condense the separate filaments of each set into one strand, and as the surface of the filaments are gummy and adhesive it is found on drying that they have agglutin-ated into a compact single fibre of raw silk. In the most approved modern filatures there is a separate cocoon boiler (cuiseuse), an oblong tank containing water boiled by steam heat. In these the cocoons are immersed in rectangular perforated boxes for about three minutes, when they are transferred to the beating machine (batteuse), an earthenware trough having a perforated false bottom through which steam keeps the water at a temperature of from 140° to 160°. In this water the cocoons are kept stirring by small brushes rotated by mechanical means, and as the silk softens the brushes gradually rise out of the water, bringing entangled with them the loose floss, and thereby revealing the main filament of each cocoon. The cocoons are next, in sufficient number, transferred to the reeler's tray (bacinella), where the water is heated to about 120°. From the tray the filaments are carried through a series of porcelain and glass eyelets, so arranged that the strand returns on itself, two portions of the same strand being crossed or intertwisted for rounding and consolidation, instead of the croissage of two separate strands as in the old method. The reel to which the raw silk is led consists of a light six-armed frame, enclosed within a wooden casing having a glass frame in front, the enclosure being heated with steam-pipes. To keep the strands from directly overlaying each other and so adhering, the last guide through which the silk passes has a reciprocating motion whereby the fibre is distributed within certain limits over the reel. A sectional view of the reeling apparatus and arrangementsnow in common use in Italyis shown in fig. 12.
Throwing.Raw silk, being still too fine and delicate for ordinary use, next undergoes a series of operations called throwing, the object of which is to twist and double it into more substantial yarn. The first operation of the silk throwster is winding. He receives the raw silk in hanks as it is taken from the reel of the filature, and putting it on a light reel of a similar construction, called the swifts, he winds it on bobbins with a rapid reciprocating motion, so as to lay the fibre in diagonal lines. These bobbins are then in general taken to the first spinning frame, and there the single strands receive their first twist, which rounds them, and prevents the compound fibre from splitting up and separating when, by the subsequent scouring operations, the gum is removed
which presently binds them into one. Next follows the operation of cleaning, in which the silk is simply reeled from one bobbin to another, but on its way it passes through a slit which is sufficiently wide to pass the filament but stops the motion when a thick lump or nib is presented. In the doubling, which is the next process, two or more filaments are wound together side by side on the same reel, preparatory to their being twisted or thrown into one yarn. Bobbins to the number of strands which are to be twisted into one are mounted in a creel on the doubling frame, and the strands are passed over smooth rods of glass or metal through a reciprocating guide to the bobbin on which they are wound. Each separate strand passes through the eye of a faller, which, should the fibre break, falls down and instantly stops the machine, thus effectually calling attention to the fact that a thread has failed. The spin-ning or throwing which follows is done on a frame with upright spindles and flyers, the yarn as it is twisted being drawn forward through guides and wound on revolving bobbins with a reciprocat-ing motion. From these bobbins the silk is reeled into hanks of definite length for the market. Numerous attempts have been made to simplify the silk-throwing by combining two or more operations on one machine, but not as yet with much success.
According to the qualities of raw silk used and the throwing operations undergone the principal classes of thrown silk are(1) " singles," which consist of a single strand of twisted raw silk made up of the filaments of eight to ten cocoons; (2) tram or weft thread, consisting of two or three strands of raw silk not twisted before doubling and only lightly spun (this is soft, flossy, and comparatively weak); (3) organzine, the thread used for warps, made from two and rarely three twisted strands spun in the direction contrary to that in which they are separately twisted. Silks for sewing and embroidery belong to a different class from those intended for weaving, and thread-makers throw their raw silks in a manner peculiar to themselves.
Numbering of Silk. The numbering (titrage) of raw and thrown silks, by which the size or fineness of the yarn is stated, is deter-mined by constant length with variable weight, whereas other yarns are indicated by constant weight with variable length. The original standard length was 9600 Paris ells = 11,400 metres, the number being the weight in deniers of 24 grains = 1'275 grammes. This still remains the most common standard, and in practice the number is ascertained by the weight in grains, _____ of a denier of a hank containing 476 metres (properly 475____ metres = 400 Paris ells). According to this standard a single cocoon filament weighs 2 to 3 5 deniers, a 3 to 4 cocoon strand ranges from 7 to 10 deniers, and a 16 or 17 cocoon strand is numbered from 48 to 52. Spun silk is numbered on a different principle. In the United Kingdom it is determined by the cotton standard, the number of skeins of 840 yards per lb. In Continental manufacturing centres generally the standard is the number of eeheveaux of 500 metres contained in a half kilogramme, or, more simply, the number of kilometres per kilogramme. According to the resolution of the international congress for promoting uniformity in the numbering of yarns, held at Vienna in 1873 and at Brussels in 1874, the grade of silk ought now to bo expressed by ten times the number of grammes given by a hank of 1000 metres.
These methods of indicating grades of silk give, however, only the most imperfect idea as to the quality of the thread; and | specially they convey no information as to uniformity of diameter ; and strength. To test the raw material in respect of uniformity a most ingenious American invention, the serigraph, has been introduced, and is now largely used. The serigraph has two reels mounted on one spindle, or at least so arranged that they make precisely the same number of revolutions. The reels are covered with india-rubber, and No. 2 is 3 per cent, greater in circumference than No. 1. The silk to be tested is placed on No. 1 reel and from that wound on No. 2, which, being of greater diameter, puts a certain amount of strain on the elastic fibre. In passing from the one reel to the other the silk is carried over an agate hook attached to the bob of a pendulum, so that the strain on the yarn is communicated to the pendulum. The strain caused by the 3 per cent, tension of course varies with the strength of the yarn to which it is applied, being greater with increased strength and thickness, and falling away just as the strength of the yarn decreases. Thus the yarn in passing over the agate hook keeps by its tension the pendulum at one particular position while it is uniform, but when it increases in strength it raises the pendulum higher, and when it becomes weaker the pendulum falls. To the extremity of the pendulum is attached a pencil or marker, which traces on a web of paper, travelling at a rate in fixed proportion to the winding, the changes in the pendulum, and thus is obtained a graphic record in a most distinct manner of every variation in the strength of the silk. The precise spot where any imperfection occurs is shown on the tracing, which thus not only absolutely certifies the quality of the yarn, but also automatically measures the quantity reeled.
Conditioning. Silk in the raw and thrown state, as has already been pointed out, absorbs a large amount of moisture, and may contain from 20 to 30 per cent, of water without being manifestly damp. As it is largely sold by weight it becomes necessary to ascertain its condition in respect of absorbed water, and for that purpose official conditioning houses are established in all the con-siderable centres of silk trade. In these the silk is tested or con-ditioned, and a certificate of weight issued in accordance with the results. The silk is for four hours exposed to a dry heat of 230° Fahr., and immediately thereafter weighed. To the weight 11 per cent, is added as the normal proportion of water held by the fibre.
Scouring. Up to this point the silk fibre continues to be comparatively lustreless, stiff, and harsh, from the coating of albuminous matter (gum or gres) on its surface. As a preliminary to most subsequent processes the removal of the whole or some portion of this gum is necessary by boiling-off, scouring, or decreumge. To boil off say 300 lb of thrown silk, about 60 lb of fine white soap is shred, and dissolved in about 200 gallons of pure water. This solution is maintained at a heat of 195°, and in it the hanks of raw silk are immersed, hung on a wooden rod, the hanks being con-tinually turned round so as to expose all portions equally to the solvent influence of the hot solution. After being dried, the hanks are packed in linen bags and boiled for three hours in a weaker soapy solution, then washed out in pure warm water and dried in a centrifugal hydro-extractor. According to the amount of gum to be boiled off the soap solutions are made strong or weak; but care has to be exercised not to overdo the scouring, wdiereby loss of strength, substance, and lustre would result. For some purposesmaking of gauzes, crapes, flour-bolting cloth, and for what is termed ''souples "the silk is not scoured, and for silks to be dyed certain dark colours half-scouring is practised. The perfect scouring of French silks removes from 25 to 27 per cent, of their weight, and Chinese silks lose from 30 to 31 per cent. Scouring renders all common silks, whether white or yellow in the raw, a brilliant pearly white, with a delicate soft flossy texture, from the fact that the fibres which were agglutinated in reeling, being now degummed, are separated from each other and show \ their individual tenuity in the yarn. Silks to be finished white are at this point bleached by exposure in a closed chamber to the fumes of sulphurous acid, and at the close of the process the hanks are washed in pure cold water to remove all traces of the acid.
Spun Silk Manufacture.The materials of the spun silk trade are(1) the floss or loose outer fibres which surround ordinary cocoons ; (2) the remains of cocoons after the reelable silk has been removed; (3) waste from throwing processes and from all the I stages through which reeled silk passes in manufacturing ; (4) unreelable cocoons, i.e., those which are pierced, torn, or cut, stained by dead chrysalides, &c., and double cocoons; (5) cocoons of various wild silks, which are either unreelable or most profitably worked by carding. The waste spinners' first duty is to bring these diverse materials into uniform fibrous condition for spinning. In dealing with cocoons and cocoon husks, the fibres, which are gummed together into a dense compact mass, must be so washed, softened, and freed from each other that they can be readily teased and torn into a tow-like mass. For this purpose they are washed with a strong hot soap solution in a revolving washing machine, in which they are continuously subjected for three or four hours to the action of falling stampers. From this treatment they are taken to the cold-water washing machine, where they are treated with a continuous spray of pure water whilst revolving in the tub under the action of falling stampers, as in the hot-water machine. Next the cocoons are rinsed in a spray of pure water, then the moisture is expelled in a hydro-extractor, and so, thoroughly degummed and softened, they are allowed to dry. For further treatment they are damped with a sprinkling of weak solution of Marseilles soap, then beaten either with the hand or by means of a machine. This machine has a series of leather straps attached to an endless band, which by its rapid revolution causes the straps to hit with a quick whipping stroke against the surface of a revolving tray on which are placed the washed cocoons. The beating serves to free the fibres fully from each other, and expels in the form of a fine dust the remains of chrysalides from the interior of the cocoons. It now remains only by the operation of the cocoon opener to tease out and separate the fibres into a kind of lap. The cocoon-opener is a modified carding machine, the drum or cylinder of which is covered with strong card teeth. On this drum the fibres collect as they are opened and teased out, and wdien the teeth are full the lap so formed is stripped off by the attendant. The silken fibres are now ready for the operations preparatory to spinning.
To bring raw waste other than cocoons to this point a different series of operations are necessary. The removal of the gum is first usually effected by a process of fermentation or maceration instead of washing with soap, whereby a great saving of soap is secured. Into a large tank a quantity of waste is packed, and soaked with a weak soapy solution which is maintained by steam at about 170°. The tank is closed over, and in the course of a few days fermenta-tion begins, and according to circumstances is allowed to go on from two to three weeks. From time to time proof samples are withdrawn to observe the progress of the rotting, as over-fermentation would result in the same injury which arises from over-scouring, weakness of fibre, loss of lustre, and waste of substance. By maceration the silk loses from 20 to 30 per cent, of its weight. From the maceration vat the silk is conveyed to the hot-water washing machine, where with a weak soapy solution it is washed under the influence of stampers for about five minutes. Great care is necessary to prevent the silk from cooling before this washing, as thereby the macerated slime would form an almost insoluble deposit on the silk fibre. From the hot soap solution the silk is taken to the cold-water machine, where, with the aid of stampers, it undergoes a thorough and prolonged washing. After being hung over hurdles to dry it is sprinkled with a weak solution of Marseilles soap, and then dried by means of the hydro-extractor and subsequent exposure in a heated well-ventilated chamber. At this point both cocoon waste, as already described, and floss waste are in the same condition.
The spinner has now to deal with a mass of entangled fibres of all lengths, which he must render even, parallel, and comparatively uniform in length before it can be spun. The fibres are slightly damped with a weak soapy solution and taken to a filling drum, which consists of a large cylinder having set into it, parallel with its axis, from twelve to twenty rows of strong steel spikes. A feeding apron of cloth covered with card-teeth is provided to the machine, and, as the fibre is carried forward towards the drum, a similar card-teeth-covered band travels close over the surface of the apron, so that the fibre is presented to the drum from between two sets of card-teeth. The rows of spikes catch the fibre as presented to them, draw it through the card-teeth, and carrying it with them lap it around the drum in regular eombed-out order. When the spikes are sufficiently filled, the lap is cut at each set of spikes, and so stripped from the drum it forms a definite number of "stricks," of the breadth of the drum itself and the length of the space between the sets of spikes. These stricks are caught in wooden clamps or "books," which are fastened in the bed of the fiat dressing frame. Over them an endless band travels, having on it at short intervals belts of heckle-teeth, called combs, which comb out doubled and short fibres, and, acting first on one end of the strick and next on the other, leave the silk in the condition of beautifully parallel and comparatively uniform flakes. The product of the first combing, called the first draft, is the longest and purest fibre. The material combed out as it fills the comb teeth is caught in hooks, and when itself combed out forms second drafts, shorter and less valuable than the first; and again the combings of second drafts, when combed, form third drafts still shorter. In this way five or six separate drafts or combings from the original lap are obtained, all increasingly short and impure. The final combed waste is treated by a different process for making noil or bourette yarn.
A new form of dressing-frame is now coming into favour, in which the stricks of silk have their ends rolled round wooden rods, and so secured between wooden clamps on the surface of a huge cylinder which revolves so slowly that the attendant can change and fill the clamps as the drum goes round. In its revolution the exposed portion of the silk is first combed on one side by a rapidby revolving card-toothed cylinder, from which it passes onwards to meet a second similar cylinder revolving in a contrary direction, which combs the opposite side. In the second revolution of the cylinder the portion of the strick which was previously wound on the rod is similarly combed on both sides, and. thus the entire strick is rendered smooth and parallel.
The above is an outline of the ordinary process of preparing silk waste as practised in Switzerland and in the United Kingdom, &c, the range of machines being that of Messrs Greenwood and Batley of Leeds. In the great Manningham silk mills at Brad-ford, Mr S. C. Lister, the well-known inventor of wool-combing machinery, while using machinery of the class described, treats by patented methods peculiar to himself a great proportion of his material. According to his original process, scoured, teased, and opened waste is first drawn into a lap on a screw gill box. These laps, containing all the fibres both long and short, are taken to the circular nip combing machine, where the " top " of long fibre is drawn out as a continuous sliver and separated from the " noil" or short fibre, which according to its length is delivered at separate points. In his most recent mode of working, Mr Lister forms his waste into a broad lap on the large drum of a kind of carding engine, the drum being stripped when its teeth are filled with the prepared fibre. These laps are laid on the feeding table of a machine which has an oscillating or rocking filling head. At each oscillation the end of the lap in front of the table is " filled " on to a row of heckle-teeth parallel with it, and just as the feeding-table recedes a knife comes down between the heckles and the table with a sudden stroke and separates from the lap such fibres as have been placed or filled on to the heckle-teeth. These heckle-teeth in the meantime, being fixed on an endless band, are continuously moving forward in a horizontal direction parallel with the front of the feeding machine, and a set of three such machines place a portion of their laps on to the heckle-teeth in their progress, thus tilling the teeth with a fair '' bite" of silk. Immediately the heckles have passed the machines, the silk is caught and cleaned off the endless comb by pairs of endless revolving nips rising from under and descending from above, and between these nips the stricks are carried forward in the same horizontal line in which they travelled on the heckle-teeth, which here begin their return journey to be again filled. The stricks in their progress are now submitted to the combing action of revolving card-covered cylinders and card-covered cloth. Half way on in its horizontal path a second set of endless nips seize the combed portion of the silk, the uncombed portion held between the first set is released, and it in its turn is submitted to the combing action of cylinders and endless card-bands. In the end the fully dressed stricks of silk fall on a narrow feeding cloth, which has a combined reciprocating and forward motion, so that the material is spread with the utmost regularity and evenness. It passes through a set of screw gills, and is delivered into cans in the form of a most uniform and equal continuous sliver. The great advantage of these machines is the small amount of tending they require and the large quantity of dressed silk they deliver with unerring regularity.
The spinning proper of dressed waste is done precisely as in the spinning of flax yarn. The flakes are formed into a broad sliver on the spreading frame, and further attenuated and equalized on the set frame and the drawing frame, from which last the silk passes to the roving frame, where it receives its first preliminary twist and is sufficiently condensed to wind on a bobbin. The rovings are finally elongated and spun on the ordinary spinning frame, and for twisting into thread the yarns in two, three, or more strands are wound together on the doubling frame, and finally twisted as in dealing with raw silk spinning.
Spun silk, as it comes from the spinning frame, shows a good many nibs and irregularities and some roughness of surface. To remove these it is wound from one bobbin to another over an improving or cleaning and gassing machine, which consists of a frame having attached to it a number of small cone rollers, around which the yarn passes in a way which makes the entering portion of the thread rub against the portion running off. In this way, with considerable rubbing, the yarn cleans itself; and in its course over the rollers it rapidly passes through a gas flame, which singes off the fine projecting fibres, leaving the yarn clean, round, and compact. It is submitted to a further examination by eye and hand after being wound into hanks ; and some yarns are finally dressed with albumen and gum solutions.
In the combing of waste silk as much as from 25 to 30 per cent, of waste in a second degree arises, much of which is very short, full of nibs and dust. From this a lower quality of yarn is spun, called noil yarn, and on the Continent " bourette " silk, to distinguish it from the '' floret" silk made from first waste. On account of the shortness of staple it is worked up by machinery different from that used in the floret manufacture, being prepared by carding, and combed out with a modification of Heilmann's or Lister's combing machines. The finished noil yarn is very lumpy, and requires severe improving and singeing.
Spun silk lacks the smoothness, brilliance, and strength of raw-silk yarn, but still it is an extremely valuable and useful material, and its comparative cheapness gives it an important place among the products of textile industry. It is used very largely in mixed fabrics, as well as for the cheaper ribbons, velvets, hat plush, and for many other silk woven fabrics, as also in the hosiery and glove trades and for sewing, knitting, and embroidering yarns.
Silk Weighting.Into the dyeing of silk it is not here necessary to enter, except in so far as concerns a nefarious practice, carried on in dye-houses, which has exercised a most detrimental influence on the silk trade. Silk, we have seen, loses about one-fourth of its weight in scouring. To obviate that loss it has long been the prac-tice to dye some dark silks "in the gum," the dye combining in these cases with the gum or gelatinous coating, and such silks are known as "souples." Both in the gum and in the boiled-off state silk has the peculiar property of imbibing certain metallic salts largely and combining very firmly with them, the fibre remaining to external appearance undiminished in strength and lustre, but much added to in size and weight. Silk in the gum, it is found, absorbs these salts more freely than boiled-off; so to use it for weighting there are these great inducementsa saving of the costly and tedious boiling-off, a saving of the 25 per cent, weight which would have disappeared in boiling, and a surface on which much greater sophistication can be practised than on scoured silk. In dyeing a silk black a certain amount of weight must be added ; and the common practice in former times was to make up on the silk what was lost in the scouring. Up to 1857 the utmost the dyer could add was "weight for weight," but an accidental discovery that year put dyers into the way of using tin salts in weighting with the result that they can now add 40 oz. per lb to scoured silks, 120 oz. to souples, and as much as 150 oz. to spun silks, and yet call these compounds "silk." Not only so, but the use of tin salts, especially stannic chloride, SnCl4, enables dyers to weight all colours the same as black. In his "Report on English Silk Industry" to the Royal Commission on Technical Instruction (1885) Mr Thomas Wardle of Leek says ;
"Colours and white of all possible shades can very easily be imparted to this compound of silk and tin, and this method is becoming extensively used in Lyons. Thus weighting, which was until recently thought to apply only to black silks, and from which coloured silks were comparatively free, is now cheapening and deteriorating the latter in pretty much the same ratio as the former. Thus the proto- and per-salts of iron, as well as the proto- and per-salts of tin, including also a large variety of tannin, sumac, divi-divi, chestnut, valonia, the acacias (Areca Catechu and Acacia Catechu from India), from which are obtained cutch and gambier, *fec, are no longer used solely as mordants or tinctorial matters, but mainly to serve the object of converting the silk into a greatly-expanded fibre, consisting of a conglomeration of more or less of these substances."
Sugar also is employed to weight silk. On this adulterant Mr Wardle remarks :
"With a solution of sugar, silk can have its weight augmented from 1 oz. to 3 oz. per lb. I am not quite sure that this method of weighting was not first used by the throwsters, as sugar is known to have beuii used for adulterating and loading gum silk for a very long time, and then the idea was afterwards applied to silk after the dyeing operations. It is much resorted to for weighting coloured silks by dyers on the Continent, and, though a very clumsy method, no substitute has been found so cheap and easy of application. Bichloride of tin, having chemical affinity for silk fibre, bids fair to extinguish the use of sugar, which, from its hygrométrie qualities, has a tendency to ruin the silk to which it is applied, if great care be not taken to regulate the quantity. There is not the slightest use or excuse for the application of sugar, except to cheapen the silk by about 15 to 20 per cent."
Wild Silk Dyeing.Among the disadvantages under which the silks of the wild moths long laboured one of the most serious was the natural colour of the silks, and the extreme difficulty with which they took on dyes, specially the light and brilliant colours. For success in coping with this difficulty, as well as in dealing with the whole question of the cultivation and employment of wild silks, the unwearying patience and great skill of Mr Thomas Wardle of Leek deserve special mention here. The natural colour of tussur silk is a greyish fawn, and that shade it was found impossible to discharge by any of the ordinary bleaching agents, so as to obtain a basis for light and delicate dyes. Moreover, the chemical character of the tussur silk differs from that of the mulberry silk, and the fibre has much less affinity for tinctorial substances, which it takes up unevenly, requiring a large amount of dye-stuffs. After protracted experimenting Mr Wardle was able in 1873 to show a series of tussurs well-dyed in all the darker shades of colour, but the lighter and bright blues, pinks, scarlets, &c., he could not produce. Subsequently the late M. Tessie du Motay found that the fawn colour of natural tussur could be discharged by solution of permanganate of potash, but the oxidizing action was so rapid and violent that it destroyed the fibre itself. Gentler means of oxidation have since been found for bleaching tussur to a fairly pale ground, but the dyeing of light colours cannot yet be said to he a commercial success. The silk of the eria or castor-oil worm (Attacus ricini) presents the same difficulties in dyeing as the common tussur. A portion of the eria cocoons are white, wdiile the others are of a lively brown colour, and for the dyeing of light colours the latter require to undergo a bleaching process. The silk takes up colour with difficulty from a strong vat, and is consequently costly to dye. Moonga silk from Anthereea assama has generally a rather dark brown colour, but that appears to be much influenced by the leaves on which the worm feeds, the cocoons obtained on the champaea tree (Michelia champaca) giving a fine white fibre much valued in Assam. The dark colours are very difficult to bleach, but the silk itself takes dye-colours much more freely and evenly than either tussur or eria silk.
Trade and Commerce.
About the commencement of this century the chief silk-producing regions of the world were the Levant (including Broussa, Syria, and Persia), India, Italy, and Prance, the two first named sending the low-priced silk, the other two the fine qualities. Between 1840 and 1850, after the open-ing of trade with China, large quantities of silk were sent from the northern port of Shanghai, and afterwards also from the southern port of Canton. The export became important just at the time when disease in Europe had lessened the production on the Continent. This increased production of medium silk, and the growing demand for fine sorts, induced many of the cocoon-growers in the Levant to sell their cocoons to Europeans, who reeled them in Italian fashion under the name of " Patent Brutia," thus producing a very fine valuable silk. In 1857 commenced the importation of Japan silk, which became so fierce a competitor with Bengal silk as gradually to displace it in favour; and recently the native silk reeled in Bengal has almost ceased to be made, only the best European filatures, produced under the supervision of skilled Europeans, now coining forward.
China and Japan, both of which contribute so largely to the supplies that appear in European and American statistics, only export their excess growth, silk weaving being carried on and native silk worn to an enormous extent in both countries. The other Asiatic exporting countries also maintain native silk manufactures which absorb no inconsiderable proportion of their raw material. The silk production of the world, including only the amount exported from these Oriental countries, amounts on an average to from 20,000,000 lb to 25,000,000 lb yearly; but the crop is subject to great variations.
The supply available for European consumption during recent years was thus stated, in bales of 100 lb, by the Moniteur des Soies of Lyons, 25th July 1885 :
== TABLE ==
While these tables indicate remarkable fluctuation of supply they show generally that Asiatic countries, besides supplying their own considerable demands, send to Europe fully one half of the whole silk consumed in Western manufactures. China stands first as a silk-producing country, yielding about 35 per cent, of the entire supply; the whole produce of Italy amounts to nearly the same proportion ; the exports of Japan account for about 12 per cent, of the annual supply; while in recent years France and the Levant are credited with about equal proportions.
In the United Kingdom the trade in raw silks has been in a condition of decline for a considerable number of years, much of the Chinese and Eastern produce which formerly came to London now being unshipped at Marseilles, and sold in the Lyons market, which has become the leading-silk mart. But there is a very steady and continuous expansion in the demand for waste silks and cocoons for the spun silk trade. The following figures show the official annual returns of silk imports since 1860, the date of the French commercial treaty, which exposed many branches of the trade to severe and fatal competition :
== TABLE ==
The sources whence the English imports of raw silk, the commercial names under which they pass, and their relative importance and values, are exemplified in the following table, extracted from the annual circulars issued by Messrs H. W. Eaton & Sons of London :
== TABLE ==
In the manufacture of silken fabrics France occupies the most important position among the nations. Not only is the whole of the raw silk produced in France worked up within the country, but a very considerable proportion of that imported from the Levant and from Asia passes into the hands of the French manufacturers. In all, between 8,000,000 and 9,000,000 lb of raw silk are on an average manufactured into various textures in France. Lyons is the headquarters of the trade, and, if the surrounding regions be included, employment is given to about 120,000 looms,20,000 of which are driven by power,principally in the production of dress silks, plain and figured, and in other heavy silken fabrics, and at St Etienne and St Chamond in the ribbon trade. There are also important manufactures of silk at Calais, St Pierre les Calais (tulles and passementerie), Paris, Mmes, Tours, Avignon, and Roubaix. Next to France in the extent and value of manufactures comes Germany, where the principal seat of the silk trade is at Crefeld, nearly one half of the whole production of the empire being manu-factured there. The looms of Crefeld and the district it controls numbered in 1881 about 33,000, and the trade was flourishing and expansive. The manufacture of union velvets is the special feature of the industry, about one half of the looms being devoted to that textile; but Crefeld controls also a large trade in union satins, and pure silk broad goods and ribbons of all kinds. The whole value of its trade amounted in 1881 to almost £1,000,000, one-fourth of which found a market in England, and about a quarter of a million went to France. The other principal centres of the silk trade, all in Bhenish Prussia, are Viersen, Barmen, Elberfeld, and Mühlheim. Third on the list of Continental producers is Switzerland, where Zurich takes the lead with broad goods (failles, armures, satins, serges, &c), and Basel rivals St Etienne in the ribbon trade. The number of looms throughout the country is estimated at 40,000, of which 4000 are power-looms. Italythe early home of the silk trade, the land of the gorgeous velvets of Genoa and the damasks and brocades of mediaeval Sicily, Venice, and Florencehas fallen from its high estate, and now employs not more than 30,000 looms, the centre of greatest activity being at Como; but Genoa still makes velvets, and the brocades of Venice are not a thing of the past. In Austria the silk trade has found its principal development in Vienna and its immediate neighbourhood, the number of looms throughout the entire empire being estimated at from 15,000 to 20,000, of which 2000 are power-looms. In Bussia there is, with a growing cultivation of raw silk, a considerable and in-creasing manufacture, the special feature of which is the weaving at Moscow of gold and silver tissues and brocades for sacerdotal use, and for traffic with Central Asia.
In the United Kingdom all the silk industriesthese depending on spun silk alone exceptedhave been in a depressed and declining condition ever since 1860. The principal silk manu-facturing towns of England have been Coventry, Macclesfield, Congleton, Leek, Derby, London (Spitalfields), Manchester, Middleton, and Nottingham, and it is estimated that at the best period not fewer than 150,000 looms found employment in the trade. In 1872 that number was reduced to 65,000, of which 12,500 were power-looms. Spitalfields in her best days (about 1825) kept 24,000 hand-looms occupied; now there are not more than 1200. Manchester once had about 20,000 looms weaving silk; now there are not 6000 so employed. When the French treaty of 1860 came into operation Coventry had about 9000 looms, principally employed in ribbon weaving ; now not more than one-fourth of that number are in operation. The cause of several of these severe changes is to be found in the introduction of the factory system of working and the extension of power-loom weaving, which crushed out domestic weaving, the original form of the silk industry ; but undoubtedly also the English manufacturers were beaten in the battle of free competition brought on by the French treaty. On the other hand, the remarkable development of the
== TABLE ==
comparatively new trade in spun silk goes far to compensate for the loss of the older trade, and has enabled the exports of silk manufactures from the country to be at least maintained and to show some signs of expansion. The spun-silk industry has chiefly developed in the Yorkshire and Lancashire textile centres, Bradford, Halifax, Rochdale, &c. But it is highly significant that, while the exports of British silk manufactures have not decreased, the imports in the meantime have shown a marked expansion ; and unquestionably, although the use of silken goods has increased very greatly within twenty-five years, the expansion of native silk manufactures has not kept pace with that growth.
Favoured by the operation of protective duties ranging from 50 to 60 per cent, ad valorem, the native manufacture of silk in the United States has been nursed into considerable activity and expansion, till now well-nigh one-half of the silken fabrics used in the country are of home manufacture. In 1860 the proportion of native manufacture was 13 per cent., in 1880 it reached 38 per cent., and in 1882 it was 40 per cent, of the entire consumption. Reeled silks are principally manufactured at Paterson and Hoboken, N. J., and Brooklyn and New York City, N. Y., and the spun-silk industry nourishes at South Manchester and
== TABLE ==
Other countries... 17,000,000 The following estimate of the relative importance of the silk manufacture of various countries was made in 1883 by Mr Peixotto, the United States consul at Lyons :
== TABLE ==
1 The figures relating to Tsatlee comprise Re-reel, Hangehow, and Yuun-fa.
2 The figures relating to Taysaam comprise Tussah.
The above article was written by: James Paton. Curator, Galleries of Art, Glasgow.