CHAPTER II.. Manufacture of Silk by the Silkworm.

MANUFACTURE OF SILK BY THE SILKWORM.

We now come to the most important of all silk-spinning insects, the common silkworm, or caterpillar of the mulberry-tree moth. The labours of this insect were known and appreciated in other parts of the world long before we had tidings of its existence; so that the peasantry of other lands were clad in raiment which our kings would have been proud to wear. “When silk was so scarce in this country that James the First, while King of Scotland, was forced to beg of the Earl of Mar the loan of a pair of silk stockings to appear in before the English ambassador, enforcing his request with the cogent appeal, ‘for ye would not, sure, that your king should appear as a scrub before strangers;’ nay, long before this period, even prior to the time that silk was valued at its weight in gold at Rome, and the Emperor Aurelian refused his empress a robe of silk because of its dearness, the Chinese peasantry in some of the provinces, millions in number, were clothed with this material; and for some thousand years to the present time, it has been both there and in India (where a class whose occupation was to attend silkworms appears to have existed from time immemorial, being mentioned in the oldest Sanscrit books,) one of the chief objects of cultivation and manufacture. You will admit, therefore, that when nature

——Set to work millions of spinning worms, That in their green shops weave the smooth-haired silk To deck her sons,

she was conferring upon them a benefit scarcely inferior to that consequent upon the gift of wool to the fleecy race, or a fibrous rind to the flax or hemp plants; and that mankind is not under much less obligation to Pamphila, who, according to Aristotle, was the discoverer of the art of unwinding and weaving silk, than to the inventors of the spinning of those products.”

EGGS AND SILKWORMS IN THE FIRST AGE. ]

It is so common an amusement with young persons in this country to procure the eggs of silkworms, rear the insects, and watch their changes that numbers are acquainted with the growth, habits, and manner of spinning of these interesting creatures. Perhaps a sheet of paper is given to a little boy or girl, on which are a number of small specks, no bigger than pins’ heads: these specks, the child is told, are silkworms’ eggs, and if he keeps them dry during winter, and then places them in a sunny window in spring, he will get a number of caterpillars from them. Taking care to do this, the child is delighted some fine morning to see a few little dark coloured worms crawling about the paper, while others are just issuing from the eggs. Perhaps a difficulty now arises about their food. In warm countries the leaves of the mulberry-tree are ready for the insects as soon as they are hatched; but in England, unless the eggs are purposely kept back, by putting them in a cold place, the caterpillars come out before the mulberry-tree has put forth its leaves. A few tender leaves of the lettuce are therefore spread lightly over the young caterpillars, and upon these they mount, and at last begin to feed, after searching in vain for their natural food. But the worms do not thrive on this diet, and it is much better so to manage the eggs that they may be hatched when the young leaves of the mulberry are just opening. These form the best possible food in that tender state, and in order to economise it, the leaves should be cut in small pieces; because the caterpillars feed only on the edges, and thus great part of a leaf, when given to them whole, is entirely wasted.

THE WHITE MULBERRY.

(Morus alba.) ]

In Italy, where great attention is paid to the cultivation of the silkworm, the eggs are hatched in a room heated by a stove, and the young caterpillars are then removed on their mulberry-leaves to a cooler apartment called the nursery, where they are managed with great care and skill. Wicker shelves are arranged in the room at convenient distances, and are lined with paper, on which the worms are placed. Care is taken to place together only such worms as are hatched at the same time, for without this precaution the treatment, with respect to food, could not be regulated, and the moultings would not take place at the same time. Great care is also taken to secure the worms from rats and mice, as well as from certain insect enemies.

Silkworms are so little disposed to wander away from their food that open trays are sufficient to secure them: but unless great cleanliness is observed in their management, and frequent change of food given, a sickly smell is observed, and the caterpillars languish and die in great numbers. Supposing the young brood goes on well, and is properly attended by the child whom we have supposed to undertake the charge, there will be about five or six days’ feeding, and then the worms will begin to sicken for their first moult, or casting the skin. Silkworms have four of these moults, at each of which they appear to suffer pain or inconvenience; they also entirely leave off eating for two or three days. The caterpillars at that time raise the fore part of their bodies, and show tokens of uneasiness. They have grown rapidly, and their skins, not having grown in proportion, now appear to press and inconvenience them; but after two or three days fasting, they become thinner and are able gradually to rid themselves of their skin. It is now that their owner may see the use they begin to make of their silk. By watching them closely he sees each caterpillar throw out a number of very fine silken lines, by which it fastens the skin to one spot. Having done this, it is able to creep out, without dragging the skin about after it, as would otherwise be the case. In this operation the whole covering of the body, including that of the feet, of the jaws and teeth, is cast off; but it sometimes happens that the animal cannot entirely cast its skin, a portion of it breaking and remaining attached to the extremity of the body. As the animal increases rapidly in size, this portion of the old skin compresses its body tightly, causing inflammation and much suffering, which usually ends in death.

Worms that have newly moulted are readily distinguished by their pale colour, and the wrinkled appearance of the new skin. Soon after moulting they recover health and vigour, and feed with increased appetite. To keep them in health they must be fed with great regularity, and not crowded together in their trays. In the course of five days the rapid growth of the insect causes the wrinkles to disappear from the skin; it is now half an inch in length; a second sickness, and a second moulting, prepare it for increase of growth; it casts its skin as before, and feeds without intermission during another five days, during which time it attains a length of three quarters of an inch. It then falls sick and moults a third time. It again feeds during five days, after which it casts its skin for the fourth and last time in the caterpillar state.

PROGRESSIVE GROWTH OF THE SILKWORM. ]

It is now about one and a half or two inches in length, and devours its food most voraciously, increasing rapidly in size during ten days. When the worms are fed a slight hissing noise is heard similar to that of green wood burning. According to some writers this noise proceeds from the action of the jaws, but others attribute it solely to the action of the feet, which are continually moving until the worms have fastened to their food, when the noise ceases. In a large nursery of silkworms this noise sounds like a soft shower of rain.

SILKWORM ON MULBERRY-LEAF. ]

When the caterpillar has attained its full growth, it is a very different creature from the little black worm which first issued from the egg, being from two and a half to three inches in length, and its body consisting of twelve membranous rings, which contract and elongate as the animal moves. It is furnished with sixteen legs, in pairs: three pairs in front, under the first three rings, are covered with a shelly or scaly substance; the other five pairs, called holders, are furnished with little hooks, which assist the insect in climbing. The head is covered with a scaly substance similar to the covering of the fore legs. The mandibles are of great strength, and indented like the teeth of a saw. Beneath the jaw are two small openings, through which the insect draws its silken lines. The substance of which the silk is composed is a fine yellow transparent gum, secreted in two slender vessels, “which are wound, as it were, on two spindles in the stomach; if unfolded, these vessels would be about ten inches in length.” The insect breathes by means of eighteen holes or spiracles, distributed along the body, nine on each side. On each side of the head, near the mouth, are seven small eyes; the two specks higher up on the head, which are generally mistaken for eyes, are only parts of the skull.

FULL GROWN SILKWORM. ]

When the silkworm is ready to spin, it gets upon the leaves without eating them, rears its head as if in search of something, or crawls to the edges of the tray and moves slowly along; its rings draw in, and its greenish colour changes to a deep golden hue; its skin becomes wrinkled about the neck, and its body feels like soft dough, and on taking it in the hand, and looking through it, the whole body has assumed the transparency of a ripe yellow plum. When this is observed, the owner of the insects puts each singly into a little cone of white paper, which he pins to the wall or elsewhere, so that the creature may be undisturbed at its work. But in the nurseries abroad little bushes are set up on the wicker shelves, and the insects mount them and form their cocoons among the twigs.

Supposing the worm to be left to itself on the tray, without either of these precautions, it at last selects some corner or hollow place which will conveniently hold the cocoon it is about to spin, and begins by throwing out a number of irregular threads, which are intended to support its nest. Upon these it forms, during the first day, a loose structure of floss silk of an oval shape, within which, during the next three days, it winds the firm, hard, yellow ball, remaining, of course, all the time within it. In this operation the insect does not greatly change the position of the hinder part of its body, but continues drawing its thread from various points and attaching it to others, so that after a time the body becomes to a great extent enclosed by the thread. “The work is then continued from one thread to another, the silkworm moving its head and spinning in a zigzag way, bending the fore part of the body back to spin in all directions within reach, and shifting the body only to cover with silk the part which was beneath it. As the silkworm spins its web by thus bending the fore part of the body back, and moves the hinder part of the body in such a way only as to enable it to reach the farther back with the fore part, it follows that it encloses itself in a cocoon much shorter than its own body, for soon after the beginning the whole is continued with the body in a bent position. From the foregoing account it appears that with the most simple instinctive principles all the ends necessary are gained. If the silkworm shifted its position much at the beginning of the work, it could never enclose itself in a cocoon; but by its mode of proceeding, as above explained, it encloses itself in a cocoon which only consumes as much silk as is necessary to hold the chrysalis.”

THE COCOON.

(A portion of the floss silk has been removed.) ]

The use of the cocoon, in the natural state of the insect, is to afford a warm nest, where, secure from the inclemencies of the season, and the attacks of enemies, it may undergo its final changes. The cocoon is made water-tight by an internal lining of gum, and the silken thread of which the ball is made is also smeared with a similar gum, which hardens in the air.

THE CHRYSALIS. ]

GIRL WINDING SILK. ]

While the worm is spinning its cocoon it takes no food, and as it is continually emitting silk, its body gradually diminishes to less than half its original length. When its labour is completed it rests awhile, and then once more throws off its skin; but it is no longer a caterpillar; its form is changed into a chrysalis, or aurelia, with a smooth brown skin, and pointed at one end. A few days after the insect has finished spinning, the cocoons will be ready to be unwound. Our amateur silkworm cultivator then takes the cocoons out of the paper cones and separates the outer floss silk. He then throws several cocoons into a glass of water slightly warm, to make them more easy to unwind, and having found the ends, proceeds to wind the silk on a reel, or he gives the task to a sister’s gentler hands, while he prepares a little box of bran, in readiness to put the poor exposed chrysalis the moment it is released from the cocoon. As the winding proceeds, the cocoons become thinner and thinner until the insects within are visible. The chrysalis, though covered with a horny skin, and apparently without much sensation, shows very plainly that it is sensible of the rough treatment it is receiving, as the cocoon is tossed about in the water by the motion of the reel. It rapidly moves the rings of its tail, which is doubtless a sign of uneasiness or pain. When nearly all the silk is wound off, there still remains a transparent film like silver paper, which is torn open to let out the chrysalis. The latter is immediately buried in bran, where it remains very quietly for a week or two, then changes into a cream coloured moth, lays its eggs, and dies. This is the common domestic treatment when silkworms are kept for amusement, but in a commercial establishment such as those of Italy, they are very differently treated.

FEMALE SILKWORM MOTH AND EGGS. ]

The cocoons are collected in large quantities, separated and sorted according to their quality, about one-sixtieth part being saved for the production of eggs, after which the life of the chrysalis is destroyed in all the rest. This is done in hot countries by exposure to the sun; but in more temperate climes by artificial heat, such as that of an oven after the bread has been withdrawn. Before the cocoons can be reeled they must be separated from the floss, which is done by opening the floss covering at one end and pushing out the cocoon. Care is taken in reeling to use cocoons of one quality, as different qualities require a different treatment.

The natural gum of the cocoons is first softened in warm water, kept at the proper temperature, either by a charcoal fire or by a steam pipe. After remaining in this for a few minutes, the reeler (generally a woman) gently stirs up or brushes the cocoons with a short birch rod, and to this the loose threads of the cocoons adhere, and are thus drawn out of the water: they are then taken commonly four or five together, twisted with the fingers into one thread, and passed through a metal loop, to get rid of dirt and impurities: the thread then passes on to the reel, which is so constructed as to have a slight lateral motion, so that the thread of one revolution does not overlay the other; for if it did so, the threads would be glued together before the gum had had time to harden by exposure to the air. The threads of the four or five cocoons are thus united into one strong and smooth thread. Sometimes as many as thirty cocoons are united into one thread, and it is difficult to wind more. As often as a thread of any single cocoon breaks or comes to an end, the attendant supplies its place by a new one, so that by continually keeping up the same number the united thread may be wound to any length: these joinings are not made by a knot, but the new end is simply laid on the compound thread, to which it adheres by its gum; and as the threads are finer near their termination than at the commencement, it is necessary for the reeler to add other cocoons before the first set is quite exhausted; so that the compound thread may be of uniform thickness. The filaments of three fresh cocoons, added to two half-wound ones, make a thread about equal to that from four fresh cocoons. The cocoons are not entirely wound off, but the husk containing the chrysalis is used together with the floss silk under the name of waste. Improved methods of reeling have been introduced on the continent, but they are similar in principle to the above.

Eleven or twelve pounds of cocoons yield about one pound of reeled silk; and as from 240 to 250 cocoons weigh a pound, the number of cocoons required to produce a pound of silk may be estimated at 2,817½. The length of filament yielded by a single cocoon is 300 yards, but some have yielded as much as 625 yards.

The reeled silk is made up into hanks for sale or use. The form and contents, as well as quality, of these hanks, differ greatly, as will be seen by the following wood-cuts.

HANKS FROM ITALY. ]

BOOK OF SILK FROM CHINA. ]

SLIP FROM BENGAL. ]

We may aptly conclude our account of this most industrious silk-manufacturer in the words of the Rev. Samuel Pullein, M.A., who, so long ago as 1758, wrote an Essay on the Culture of Silk, in which the following passage occurs:—

“There is scarce anything among the various wonders which the animal creation affords more admirable than the variety of changes which the silkworm undergoes; but the curious texture of that silken covering with which it surrounds itself when it becomes a moth, and arrives at the perfection of its animal life, vastly surpasses what is made by other animals of this class. All the caterpillar kind do indeed undergo changes like those of the silkworm, and the beauty of many of them in their butterfly state greatly exceeds it; but the covering which they put on before this change into a fly is poor and mean, when compared to that golden tissue in which the silkworm wraps itself. They indeed come forth in variety of colours, their wings bedropped with gold and scarlet, yet are they but the beings of a summer’s day; both their life and beauty quickly vanish, and they leave no remembrance after them; but the silkworm leaves behind it such beautiful, such beneficial monuments, as at once record both the wisdom of their Creator, and His bounty to man.”

On the importance of the silk itself, Kirby and Spence have the following remarks:—

“To estimate justly the importance of this article, it is not sufficient to view it as an appendage of luxury unrivalled for richness, lustre, and beauty, and without which courts would lose half their splendour; we must consider it what it actually is, as the staple article of cultivation in many large provinces in the south of Europe, amongst the inhabitants of which the prospect of a deficient crop causes as great alarm as a scanty harvest of grain with us; and, after giving employment to tens of thousands in its first production and transportation, as furnishing subsistence to hundreds of thousands more in its final manufacture, and thus becoming one of the most important wheels that give circulation to national wealth.”