The quantity of silk raised in the world is enormous. Great Britain imports annu ally in the unmunnfactured state: " Raw" silk, about 6.500,000 fits. ; "waste," or knobs and husks, about 3,500,000 lbs.; besides undyed " about 5,700 lbs.; tram, about 7,000 lbs.; organzine. about 1.,9,000 lbs.; and dyed singles and tram, about 3,C00 lbs. organzine, about 10,000 lbs. Singles, tram. and organzine are terms applied to the thread after it has undergone certain cperalions (to be afterward desciiheo). The total quantity is thus about 10,000,000 lbs., if the value of ze5,000,CCO; and in addition to this we import manufactured silk goods to the value of about £12,500,000; so that the impor tance of this little insect to Great Britain alone is represented annually by about X17,500, 000. It requires 1600 worms to raise a pound of silk.
Rearing of is of the I rst consequence in the production of silk that one of the species of mulberry should i.e cultivated, end that it should be so favorably situated as to climate that its foliage is in readiness for the young worms when they are first hatched front the eggs. The spec ies Lest adapted is the v. Lite mulberry, mortis a/bd.. The extreme lateness of season at n hieh the black mulberry produces its leaves prevents its employment generally, besides which it will not bear the loss of its leaves so well. It is said that in tomb parts of China the silk-worm is easily reared upon the trees in the open air. So-litle has it a tendency to wander far from the place of its birth, if food be at hand, that it only requires a warm, dry atmosphere to bring it to per fection: but usually, even in China, and in all other countries, it is thought desirable to raise the silk-worm in properly rrranged latildings, and to supply it with mulberry leaves gathered from day to day. In India, Chitin, and other tropical countries, the eggs hatch readily at the proper time by the natural heat; but in southern Europe artifi cial heat is almost always required; formerly the heat of fermenting dung was found serviceable, and the warmth of the human body was also used, the eggs being carried in little bags in the bosom of the cultivators; hut now they are regularly hatched by 1. tove heat, beginning with a temperature of 64° Lahr., which is eradually increased through ten days to S2°, ativhieh it is maintained until the eggs are I t •1,e(1. Experience has shown that the operation is facilitated by washing the eggs in tl e first place w ith clean water; and some cultivators also wash them in wine. the value of which is very questionable. Washing is found to remove a certain gumminess and other impurities from the eggs, which would otherwise impede the hatching. When the silk-worms have been regularly developed as above described, it is usual to place above the trays various little contri vances for the caterpillar to spin wi1li nany of the Italian growers employ an ingeniously simple arrangement, which lasts mr",,ar seasons, and when not in use occupies very small space. It consists of a munber of thin slips of wood, about an inch and a half broad, and all cut sufficiently long to reach across the trays. They are each cut at intervals of an inch half through, so that one will fit into another, and when complete they all form a series of cells, which, set in a tray, form the very best receptacles for the silk-worm to spin in. When not in use, the whole arrangement can be compressed into very small compass for convenience of storage. Others use little cones of paper, or small twigs, among which the cocoons are spun.
In feedingthe worms. care is taken so to distribute the food on the shelves or in the trays that the insects shall not crowd together; and for this reason the most careful cultivators chop the leaves small, and strew them very evenly about. Great care is
taken not to let the warms of one hatch mix with those of another, unless of exactly the same age, otherwise the stronger insects would deprive the younger of their food. Many other niceties of attention are required, which altogether render the successful rearing of silk-worms a matter of touch anxiety and labor.
Preparation of the cocoons are completed, which is known by the absence of any sound within, they are'earefully sorted, and a certain number are kept for laying. The sexes are readily known by the difference of shape as well as of size, the female being plumper, and the male, besides being much smaller, having a central depression and sharper extremities. The French growers sort: them into nine varieties, those which are less compact, or in which the worm has died—a fact known by external indications—heiug separated from the good ones. When the sorting is finished, the cocoons are placed in an oven with a gentle heat, which kills the inclosed chrysalis, otherwise they would all become perforated by the insect eating through; they are then prepared for first removing the flossy covering, which is often somewhat hard and compact. cocoons are placed in basins of water, kept warm by charcoal fires, or, in the larger establishments, by steam. This softens and dissolves the natural gum which coats the silk, and makes the various coils of silk adhere together in the cocoon. The operator then takes a small brauchy twig, and stirs them about in the water. This is sure to catch hold of any liberated ends which may be floating in the water. From three to five of these ends are taken and twisted together with the fingers, so as to unite them into one thread, which is passed through a polished metal or glass eye in the reeling-machine, which is so far from the hot-water basin as to give the softened gum on the silk time to dry in its passage from the basin to the reel. In large filatures or silk establishments, complex machinery is used for winding; but reeling apparatus of the greatest simplicity is used by the Chinese, East Indians, and others with almost equal effect, when carefully done, except in the amount of work accom plished. In all eases, however, the principle is the same, and is very simple. Great care and skill are required in reeling silk from the cocoons, because, although the reeler starts wi.h four or five cocoons, not only are their individual threads apt to break, but they are not all of the same length, so thatmne will run out before the others. These Reuters are carefully watched; and as often as a thread breaks, or a cocoon rues out, another thread is joined on, and is made to adhere to the comport-id thread on tile reel by its natural gamminess. Each cocoon generally yields 300 yards of thread, so that it takes 1:200 or 1500 yards to make 300 yards of the filament of raw silk, by which name the reeled silk is always known. The raw silk,is made up into hanks of various sizes. That from China and Japan is tied in packageS of six hanks each, technically called books, and sometimes the ends of these books are covered with silken caps very curiously formed out of a single cocoon, so managed as to form a filmy cap sufficiently large to cover a man's head. The method used by the Chinese to accomplish this is quite unknown in Europe. These caps or bars, when closed, are sometimes nearly a foot square, and much of the wadding used by- the Chinese dressmakers for padding is made by placing these bags upon each other to the required thickness.