Part 11

Bubbles are round because the air which forms the inside of the bubble exerts an equal pressure in all directions. It presses equally against all sides of the bubble at the same time.

The Story in a Yard of Silk

God’s Creation and Man’s Invention.

~WHERE DOES SILK COME FROM?~

Silk in its finished state is an ideal product. It is at once durable, magnificent to the eye, tender to the touch, and its rustle is soft music to the ear. Hence it is easy to understand why the silkworm, from the earliest times, has been an object of much consideration and concern from a commercial and industrial point of view. In this country alone, we annually expend as much for silk goods as we do for public education and thirty times as much as we do for foreign missions. Such an indomitable producer of wealth is the silkworm, and a producer of wealth it has been from an age as remote as when Joseph was down in old Egypt, interpreting the dreams of King Pharaoh’s butler and baker and later that of the King himself.

To-day we speak of twenty centuries, and our minds can hardly comprehend such a lapse of time. What shall we think of the silkworm, that for twice twenty centuries has furnished practically all the raw material for the world’s silk supply? Because man’s ingenuity is at present actively engaged in the attempt to displace it by cheaper substitutes, the thought has come to us that, without going too minutely into mechanical processes, a good opportunity is presented to give some interesting information in regard to the silkworm as the creation of the Divine Hand, in contrast to the silkworm as the creation of man.

According to Chinese authority, the use of silk dates from 2650 B.C., and it is generally conceded that, in point of age, it stands midway among the great textiles, wool and cotton having preceded it, while flax, hemp and other fibrous plants followed shortly in its train.

The first patron of the silkworm was Hoang-Ti, Third Emperor of China, and his Empress, Si-Ling-Chi, was the first practical silkworm breeder and silk reeler. It is related of her that she was once walking in the palace gardens when she discovered a strange and repulsive looking worm. It was small, of a pale green color, and was feeding greedily on a mulberry leaf. She interested the Emperor in this strange creature, and, at the Emperor’s suggestion, took the fine silken web which the worm finally spun, and was the first to successfully reel the new filament and weave it into cloth. So beneficial to the nation was her work considered that her gratified subjects bestowed upon her the divine title of “Goddess of the Silkworms,” and to this day the Chinese celebrate in her honor the “Con-Con Feast,” which takes place during the season in which the silkworm eggs are hatched.

In accounting for the presence of silkworms in the garden of this early empress, we can rightly conclude that certain parts of China have always abounded in forests of mulberry trees, and that the worms themselves had existed in great numbers in a wild state and attached their cocoons to the trees for ages before any use was discovered for their web. In fact, such wild silkworms not only abound in China to-day, but have also been found in Southern and Eastern Asia, inhabiting the jungles of India, Pegu, Siam and Cochin China, but the cocoons of these worms are, naturally, of a very inferior quality, and are only used for the crudest kind of work.

Silk culture from the time of Hoang-Ti became one of the cherished secrets of China. The headquarters of the industry was in the Province of Chen Tong, where was produced the silk for the royal family. In time the silk and stuffs of China became articles of export to various portions of Asia. Long journeys were made by caravans, occupying two-thirds of a year in going from the cities of China to those of Syria, but the price obtained there exceeded the expense of the journey, and thus left a large margin of profit to the merchants. In this manner, for one thousand years, the Chinese sent their silk to the Persians who, without knowing how or from what it was made, carried it to the Western nations.

So carefully did the Orientals guard their secret, that there is reason to believe that Aristotle was the first person in the occidental world to learn the true origin of the wrought silk from Persia. In commenting on the silk which was brought from that country on the return of Alexander’s victorious army, he described the silkworm as a “horned insect,” passing through several transformations, which produced “bomby-kia,” as he called the silk. But the classics must convince one that Aristotle’s discovery did not at once become matter of current knowledge. In fact, for five hundred years after Aristotle’s time the common theory of the origin of silk among the Greeks and Romans was that it was either “a fleece which grew upon a tree” (thus confounding it with cotton), or a fibre obtained from the inner bark of a tree; and some, deceived by the glossy and silky fibres of the seed vessels of the plant that corresponds to our milk or silk weed, believed it to be the product of some plant or flower. So Virgil, in speaking of silk, says, “the Seres comb the delicate fleecings from the leaves.”

In the Sixth Century, A.D., all the raw silk was still being imported from China by way of Persia, when the Emperor Justinian, having engaged in war with Persia, found his supply of raw silk cut off and the manufacturers in great distress. His foolish legislation did not help the situation, and a crisis was averted only by two Nestorian monks, who came from China with seed of the mulberry tree and a knowledge of the Chinese method of rearing worms. No one, on pain of death, was allowed to export the silkworm eggs from China, but Justinian bribed the monks to return to that country, and in 555 they came back, bringing with them a quantity of silkworm eggs concealed in their pilgrim’s staffs. And here let us say that there has only once since been an important importation of eggs from Asia. That was about 1860, when Dr. Pasteur was making a study of a germ disease which was threatening the industry. Consequently, it can truly be said that practically all the silkworms of the Western world are descended from those brought in the eggs by the monks to Constantinople. Justinian gave the control of the silk industry to his own treasurer. Weavers, brought from Tyre and Berytus, were employed to manufacture the silk, and the whole production was a monopoly of the emperor, he fixing its prices. Under his management, the cost of silk became eight times as great as before, and the Royal Purple was twenty-four times its former price. But this monopoly was not of long duration and, at the death of Justinian in 565, the monopoly ceased, and the spread of the industry commenced in new and diverse directions.

While every detail of the growth of the industry has an unusual interest, as showing how such an insignificant thing as a worm may become a potent factor in Nature’s economy, the scope of this article will hardly allow us to more than sketch some of the other more salient points of the history of the silkworm.

About the year 910, the silkworms made their appearance in Cordova, Spain, being brought there by the Moors. From Spain silk culture soon extended to Greece and Italy.

~WHEN SILK CULTURE WAS INTRODUCED IN AMERICA~

Silk was introduced on this continent through the Spanish Conquest of Mexico, and the first silkworm eggs sold for $60.00 an ounce.

A century later royal orders were issued requiring mulberry trees to be planted in the Colony of Virginia, and a fine of twenty pounds of tobacco was imposed for neglect, and fifty pounds of tobacco was given as a bounty for every pound of reeled silk produced.

Silk culture spread rapidly in the other Colonies, and to-day the story of the ineffectual attempts to profitably rear the silkworm in this country is as voluminous as it is interesting. Suffice it to say, as a sop to our inherent Yankee pride, that silk culture was introduced into Connecticut as early as 1737, the first coat and stockings made from New England silk being worn by Governor Law in 1747, and the first silk dress by his daughter, in 1750. This State, for the eighty-four years following, led all the others in the amount of raw silk produced. In Connecticut also, was built the first silk mill to be erected on this continent for the special purpose of manufacturing silk goods. This building was constructed in 1810 by Rodney and Horatio Hanks, at Mansfield, and is still standing as an heirloom which has come to us from the infant days of the industry.

The silkworm has become domesticated, since, during the long centuries in which it has been cultivated, it has acquired many useful peculiarities. Man has striven to increase its silk producing power, and in this he has succeeded, for, by comparing the cocoon of the silkworm of to-day with its wild relations, the cocoon is found to be much larger, even in proportion to the size of the worm that makes it or the moth that issues from it. The moth’s loss of the power of flight and the white color of the species are probably the results of domestication.

This picture shows a grove of mulberry trees from which branches are being gathered as food for the worms. This is often done by the children.]

The moths are placed upon pieces of cardboard, upon which they deposit their eggs.

The cards with the eggs are kept in a cool place until the season for hatching arrives.]

This picture shows two boys preparing a bed of twigs or branches upon which the worms may spin their cocoons.]

[1] Illustrations by courtesy The Brainerd & Armstrong Co.

The foregoing pages and pictures by courtesy of Brainerd & Armstrong Silk Company, from their book entitled, “Silk, the Real versus the Imitation.”

[2] The cuts on this page and balance of cuts in the story of silk copyright by the Corticelli Silk Mills.

The silk moth exists in four states--egg, larva, chrysalis, and adult. The egg of the moth is nearly round, slightly flattened, and closely resembles a turnip seed. When first laid it is yellow, soon turning a gray or slate color if impregnated. It has a small spot on one end called the micropyle, and when the worm hatches, which in our climate is about the first of June, it gnaws a hole through this spot. Black in color, scarcely an eighth of an inch in length, covered with long hair, with a shiny nose, and sixteen small legs, the baby worm is born, leaving the shell of the egg white and transparent.

~THE SILKWORM—HOW HE DOES HIS WORK~

Small and tender leaves of the white mulberry or osage orange are fed the young worm which simply pierces them and sucks the sap. Soon the worm becomes large enough to eat the tender portions between the veins of the leaf. In eating they hold the leaves by the six forward feet, and then cut off semi-circular slices from the leaf’s edge by the sharp upper portion of the mouth. The jaws move sidewise, and several thousand worms eating make a noise like falling rain.

The worms are kept on trays made of matting, that are placed on racks for convenience in handling. The leaves are placed beside the worms, or upon a slatted or perforated tray placed above them, and those that crawl off are retained, while the weak ones are removed with the old leaves. The worms breathe through spiracles, small holes which look like black spots, one row of nine down each side of the body. They have no eyes, but are quite sensitive to a jar, and if you hit the rack they stop eating and throw their heads to one side. They are velvety, smooth, and cold to the touch, and the flesh is firm, almost hard. The pulsation of the blood may be traced on the back of the worm, running towards the head.

The worm has four molting seasons, at each of which it sheds its old skin for a new one, since in the very rapid growth of the worm the old skin cannot keep pace with the growth of the body. The periods between these different molts are called “ages,” there being five, the first extending from the time of hatching to the end of the first molt, and the last from the end of the fourth molt to the transformation of the insect into a chrysalis. The time between the four “molts” will be found to vary, depending upon the species of worm.

When the worm molts it ceases eating, grows slightly lighter in color, fastens itself firmly by the ten prolegs, and especially by the last two, to some object, and holding up its head and the fore part of its body remains in a torpid state for nearly two days.

By each successive molt the worm grows lighter, finally becoming a slate or cream white color, and the hair, which was long at first, gradually disappears. The gummy liquid which combines the two strands hardens immediately on exposure to the air.

The worm works incessantly, forcing the silk out by the contraction of its body. The thin, gauze-like network which soon surrounds it gradually thickens, until, twenty-four hours after beginning to spin, the worm is nearly hidden from view. However, the cocoon is not completed for about three days.

~SIXTY-FIVE MOTIONS OF HIS HEAD A MINUTE~

The cocoon is tough, strong, and compact, composed of a firm, continuous thread, which is, however, not wound in concentric circles, but irregularly in short figure eight loops, first in one place and then in another. In doing this the worm makes sixty-five elliptical motions of his head a minute or a total of 300,000 in an average cocoon. The motion of the worm’s head when starting the cocoon is very rapid, and nine to twelve inches of silk flow from the spinneret in a minute, but later the average would be about half this amount per minute.

Having attained full growth, the worm is ready to spin its cocoon. It loses its appetite, shrinks nearly an inch in length, grows nearly transparent, often acquiring a pinkish hue, becomes restless, seeks a quiet place or corner, and moves its head from side to side in an effort to find objects on which to attach its guy lines within which to build its cocoon. The silk is elaborated in a semi-fluid condition in two long, convoluted vessels or glands between the prolegs and head, one upon each side of the alimentary canal. As these vessels approach the head they grow more slender, and finally unite within the spinneret, a small double orifice below the mouth, from which the silk issues in a glutinous state and apparently in a single thread.

The color of the worm’s prolegs before spinning indicates the color the cocoon will be. This varies in different species, and may be a silvery white, cream, yellow, lemon, or green.

~WHEN THE SILKWORM’S WORK IS DONE~

When the worm has finished spinning, it is one and a quarter inches long. Two days later, by a final molt, its dried-up skin breaks at the nose and is crowded back off the body, revealing the chrysalis, an oval cone one inch in length. It is a light yellow in color, and immediately after molting is soft to the touch. The ten prolegs of the worm have disappeared, the four wings of the future moth are folded over the breast, together with the six legs and two feelers, or antennæ. It soon turns brown, and the skin hardens into a tough shell. Nature provides the cocoon to protect the worm from the elements while it is being transformed into a chrysalis, and thence into the moth.

With no jaws, and confined within the narrow space of the cocoon, the moth has some difficulty in escaping. After two or three weeks the shell of the chrysalis bursts, and the moth ejects against the end of the cocoon a strongly alkaline liquid which moistens and dissolves the hard, gummy lining. Pushing aside some of the silken threads and breaking others, with crimped and damp wings the moth emerges; and the exit once effected, the wings soon expand and dry.

The escape of the moth, however, breaks so many threads that the cocoons are ruined for reeling, and consequently, when ten days old, all those not intended for seed are placed in a steam heater to stifle the chrysalis, and the silk may then be reeled at any future time.

The moths are cream white in color. They have no mouths, but do have eyes, which is just the reverse of the case of the worm. From the time it begins to spin until the moth dies, the insect takes no nourishment. The six forward legs of the worm become the legs of the moth. Soon after mating the eggs are laid.

The male has broader feelers than the female, is smaller in size, and quite active. The female lays half her eggs, rests a few hours, and then lays the remainder. Her two or three days’ life is spent within a space occupying less than six inches in diameter.

One moth lays from three to four hundred eggs, depositing them over an even surface. In some species a gummy liquid sticks the eggs to the object upon which they are laid. In the large cocoon varieties there are full thirty thousand eggs in a single ounce avoirdupois. It takes from twenty-five hundred to three thousand cocoons to make a pound of reeled silk. Do you wonder that, centuries ago, silk was valued at its weight in gold?

Growers of silk in the United States, by working early and late every day during the season, which lasts from six to eight weeks, could scarcely average fifteen cents for a day’s labor of ten hours. Silk, once regarded as a luxury, is now considered a necessity.

~WHERE MAN’S WORK ON THE SILK BEGINS~

The raw silk is first assorted, according to the size of the fiber, as fine, medium, and coarse. The skeins are put into canvas bags and then soaked over night in warm soapsuds. This is necessary to soften the natural gum in the silk, which had stuck the threads together on the arms of the reel. Following the soaking, the skeins are straightened out and hung across poles in a steam-heated room, as shown in the accompanying photograph. When the skeins are dry, they are ready for the first process of manufacturing. The room we now step into is filled with “winding frames,” each containing two long rows of “swifts,” from which the silk is wound on to bobbins. The bobbins are large spools about three inches long. The bobbins filled with silk, as wound from the skeins, are next placed on pins of the “doubling frames”; the thread from several bobbins, according to the size of the silk desired, is passed upward through drop wires on to another bobbin. Should one of the threads break, the “drop wire” falls, which action stops the bobbin. By this ingenious device absolute uniformity in the size of silk is secured. The “doubling frame” is shown in one of the photographs herewith.

The bobbins taken from the “doubling frame” are next placed on a “spinner.” Driven by an endless belt at the rate of over six thousand turns a minute, the bobbins revolve, the silk from them being drawn upward on to another bobbin. This spins the several strands brought together by the “doubling process” into one thread, the number of turns depending on the kind of silk--Filo silk being spun quite slack, and Machine Twist just the reverse.