Asia. According to Latreille the city of Turfan, in Little Bucharia, was for a long period the rendezvous of the caravans coming from the east, and the chief depôt for the silk trade of China. It was the metropolis of Seres in Upper Asia, or of the Serica of Ptolemy. The expedition of Alexander into Persia and India first introduced the knowledge of silk to the Grecians, in the year 350 B.C., and with the increase of wealth and luxury in the Grecian court the demand for silk was prodigiously augmented. Thence it passed to Rome, probably about the time of Julius or Augustus Cæsar, the Emperor Heliogabalus, about the year 220, being the first who wore a robe entirely of silk. Until A.D. 550, silk in its raw state only had been sent out of China, the exportation of insects being prohibited on pain of death, and up to this period the real nature of the material was unknown. Its introduction into Europe is said to have been accomplished in the following manner.

Two Persian monks having been employed as missionaries in some of the christian churches, which, according to Cosmas, were already established in different parts of India, had penetrated into China. There, amidst their pious occupations, they viewed with a curious eye the common dress of the Chinese, the manufacture of silk, and the myriads of silk-worms, whose education, either on trees or in houses, had once been considered the labour of queens. They soon discovered that it was impracticable to transplant the short-lived insect, but that in the eggs a numerous progeny might be preserved, and multiplied in a distant climate. They observed with interest the labours of the little creature, and strove to make themselves acquainted with the manual arts employed in working up its productions into so great a variety of fabrics. On their return to the West, instead of communicating the knowledge thus acquired to their own countrymen, they proceeded on to Constantinople. The

prospect of gain, or, as some have asserted, an indignant zeal excited by seeing a lucrative branch of commerce engrossed by unbelieving nations, prompted them to impart to the emperor the secret, hitherto so well preserved by the Chinese, that silk was produced by a species of worm; and to acquaint him with their belief that the eggs might be successfully transported, and the insects propagated in his dominions. They likewise explained to Justinian the modes of preparing and manufacturing the slender filament, mysteries hitherto either altogether unknown or but imperfectly understood in Europe. By the promise of a great reward the monks were induced to return to China, and there, with much difficulty eluding the vigilant jealousy of the Chinese, they succeeded in obtaining a quantity of silkworms' eggs. These they concealed in a hollow cane, and at length, in the year 552, conveyed them in safety to Constantinople. The eggs were hatched at the proper season by the warmth of manure, and the worms were fed with the leaves of the wild mulberry-tree. These worms, in due time, spun their silk, and propagated, under the careful tendance of the monks; who also instructed the Romans in the whole process of manufacturing their production.

For a period of more than six hundred years, the production of silk appears to have been confined to the eastern empire, until Roger I., king of Sicily, on returning from his invasion of the East, introduced it into his kingdom, where it soon became an important occupation, and the manufacture of silk speedily attained a decided excellence. From Sicily we trace its progress over the greater part of Italy and Spain; and thence, under Francis I., into France.

James I. of England, stimulated by the success attending the production of silk in France during the reigns of Henry IV. and Louis XIII., made great efforts to accomplish its introduction into England. A second attempt was made in

the reign of Charles I., a third in that of George I., and a fourth very recently (1825), both in England and Ireland; but all these have proved unsuccessful, and it is now generally believed that our climate is not suited for the purpose. Although the production of silk in England is abandoned, yet its manufacture in this country is carried on to a prodigious extent, furnishing employment for more than five hundred thousand human beings. The quantity of silk annually consumed in England alone, amounts in weight to four millions of pounds; in France, Germany, Italy, Turkey, and the continent of Asia, it is also an article of great commercial importance.

Silk is spun by a caterpillar called the silk-worm, which feeds on the leaves of the mulberry-tree: this caterpillar is produced from eggs, laid by a moth in the autumn of the preceding year. In May the eggs are hatched, and produce small black caterpillars less than the tenth of an inch in length; these daily increase in size, and gradually alter their colour till they become nearly white.

In this country the caterpillar takes fifty-six days to arrive at perfection, during which time it invariably sheds its skin as many as four, and occasionally five times; the cause of this occasional additional change is not known. After every change the caterpillar is lighter in colour, and has a larger head, than previous to the change; it spins during five or six days, making about sixty-two days passed in the caterpillar state. In warmer climates the caterpillar arrives at its full growth in forty-seven days, and has finished spinning in five more, making together fifty-two days; these may be reckoned thus:- from the hatching to the first change, seven days; changing, two days; between the first and second change, seven days; changing, two days; between the second and third change, seven days; changing, three days; between the third and fourth change, seven

days; changing, four days; from the fourth change to the period of beginning to spin, eight days; spinning, five days.

When the caterpillar is about to change its skin it ceases to eat, holds its head up stiff, and appears ill and sulky; the new head is plainly to be discovered through the transparent skin, behind the old one, and rather of a triangular shape the apex of the triangle being uppermost; after remaining in this state two or three days, as above stated, the skin opens behind the head, which cracks longitudinally, and is cast with the skin; the caterpillar then twists itself from side to side, and writhes about, while the skin gradually slips from the body and comes off at the tail.

Whilst the silk-worms are feeding, they should be kept very clean and abundantly supplied with fresh leaves; open trays, made of pasteboard, are very convenient for holding them; and from these, if supplied with food, they never wander. Care should be taken to preserve silkworms from birds and mice, both of which are excessively fond of them; the influence of the sun is highly injurious to them, as are also cold north and east winds; but plenty of air, in warm weather, is beneficial. The leaves should be given to the caterpillars perfectly dry; if brought from a distance, they preserve their freshness for many days in a tin box, or on the cold bricks or stones of a cellar. After the fourth change the silk-worms require constant watching; twice a day they should be carefully looked over, and those ready to spin picked out and placed in little cells, made of writing-paper, about as large as one's thumb, open at one end and closely screwed up at the other; these paper cells may be pinned to lines crossing a room, and placed touching each other on the line.

The period of a silk-worm's being ready to spin is plainly indicated by its ceasing to eat, and becoming suddenly more transparent and of a yellow colour; it will also begin to spin

a few threads of silk among the leaves, or in a corner of the tray. The silk is elaborated in two long slender vessels lying at the sides of the stomach and intestines, and terminating in a single tube, through which the viscid fluid, of which the silken threads are composed, is forced by the peristaltic action of the muscles. This tube terminates in the centre of the lower lip of the caterpillar. Although, however, the two vessels unite into a single tube, it is evident that the silken threads are not united; since we learn from the recent microscopical investigations of Dr. Ure,* that each of the silk threads was found to be composed of two distinct cylinders, which in good silk appear to be perfectly parallel and quite cylindrical; the unevenness or the want of parallelism producing inferiority in the raw material.— Each of these cylinders varies in diameter from one twothousand two hundredth part of an inch (the measure in silk of the best quality), to one eighteen hundredth of an inch. When imported, however, several distinct threads are found to be reeled together, which is done by the grower of the silk-worms, the threads being passed through several eyelets, and then wound off. The imported raw silks are of various qualities, depending upon the mode and time of feeding, as well as upon the food of the silk-worms. These compound threads are one five hundredth part of an inch in diameter, each being divisible into eight threads; that is, into four pairs of cylinders, in the best silk. The specific gravity of silk, according to this author, is greater than had been generally supposed, being 1256 to 1200, and consequently greater than the strongest muriatic acid or water.

When placed in the paper cell the silk-worm spins a few loose connecting threads, attached to every side of the cell: it then forms a regular oval ball of silk, which is suspended

*Trans. Ent. Soc.' vol. i. Journ. of Proceedings, p. 50.