SILK, the name given to a soft, delicate, and shill ing fibre, the production of different species of larva or caterpillar. It is most commonly produced by the Phalitena bontbyx, though the Phalacna atlas is said to yield it more abundantly.
The ancients knew little concerning this substance. The manufacture of silk, including the rearing of the worms, was introduced into Europe in A. D. 555 by two monks, who, under the patronage of Justinian, brought great quantities of the worms from India to Constantinople. Athens, Thebes, and Corinth, es tablished manufactories of silk, and from them the Venetians supplied the west of Europe for many cen turies with it. From Greece the art passed to Paler mo and Calabria, from which it was propagated through Italy and Spain. It came into France a little before the time of Francis I.; and in 1489 it was in troduced into England, though so early as 1455 there was a company of silk-weavers.
The silk worm seems to be a native of China, where it has beeirreared from a very remote period. The insect remains for nearly six months in its egg, which is about the site of a pin's head. From this it emerges in the form of a caterpillar,_ with eight pair of feet. It now feeds on the leaves the mulberry or lettuce, and it increases so rapidly in size, that in six or seven days after birth its skin bursts, and the insect appears in a new form, advancing for seven days more to another stage. When the worm is about to quit its fifth skin, it then winds for itself a silken bag or cone about the site and form of a pigeon's egg, called the Cocoon. Here it throws off its last skin, and in twenty days after the transformation of the larva into the chrysalis, which is effected within the cocoon, it be comes a moth with white wings. This moth lays eggs, and these eggs about six months after produce larva as before.
It has been stated, that a fibre of silk uncoiled from a cocoon is 406 yards long, and weighs when dry three grains. One lb. avoirdupois would extend 535 miles, and forty-seven pounds would encircle the globe.
The method of rearing the silk worm may be thus shortly described:—The eggs being laid upon shallow trays of brown paper, the chopped leaves of the white mulberry are strewed over the trays. In its second or third stage, the larva are taken to larger trays, placed in a small compartment, where the tempera ture is about 75° Fahr., and an increased quantity of the leaves given them, as will appear from the subse quent tables of Count Dandolo. The trays are now removed to a large apartment, where the temperature, at first about 72° Fahr., is allowed to diminish gradu ally to 69°.
When the cocoons are ready, the nymphx within these, intended for silk, are destroyed by putting them in boiling water, and they are afterwards dried by artificial heat; but those designed for the future crop are laid out in a coarse linen cloth stretched on a table in a room not used and dark. From every lb. of cocoons (male and female) two ounces of ova or eggs may be obtained by Count Danclolo's method, as afterwards exhibited in the tables, where, if the man agement is bad, from ten to 30 lbs. may be sacrificed for a single oz. of eggs. In order to ascertain the cocoons in which the nymphx are perfect and sound, we must see if the extremities of it are less abundantly supplied with silk, and if it is confusedly arranged; when this is the case, the nympha is likely to be sound.
The male are distinguished from the female nym pita by the greater site of the latter, so that the fe male cocoons are likely to be larger than the male. The weight or 1000 male cocoons is 1700 grains, while that of as many female ones is 3000 grains.
When a proper number of each has been selected, those intended for moths are placed, as already men tioned, on a cloth in a room whose temperature does not exceed 72°, a higher temperature occasioning un healthiness. Stillness and diminished light are con sidered favourable. When the moths have deposited their eggs on the cloth, they soon die, and the ova 1825. The zero of Bellani's hygrometer corresponds with that of Saussure.