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.

in the centre of the cell, and in the interior of this it continues to work for five days. If the cells containing the spinning silk-worms are placed regularly on the line, in the order in which they begin to spin, then there will occur no difficulty in taking them off in the succession in which they stand, as the first in order on the line will be the first requiring to be wound off. After a silk-worm has been ten days in the cell, its cocoon of yellow silk will be compact and complete; this must be taken out of the cell and the exterior or waste silk stripped off, until a single thread runs by itself; an operation which will be much assisted by allowing the cocoon to float on warm water. When so much of the silk has been wound off, that the remainder appears of a thinner, paler and inferior quality, the thread should be broken, the remaining portion of the cocoon being weak, gummy, and of little value; this should be taken out of the water and laid aside, to prevent its getting entangled with the others.

Within the cocoon is the chrysalis, from which the future moth is produced; these may be thrown on a tray containing bran, which will absorb the moisture that would otherwise remain on them after their long soaking. When silk-worms are reared for profit, there is a far greater number of chrysalides than are wanted; these may be given to fowls, which are exceedingly fond of them, and to which they afford a wholesome and nutritious diet. In a fortnight or three weeks after the winding of the silk, some of the chrysalides will be found cracking and opening, and the perfect moths will then appear: these are small sluggish creatures, of a pale buff colour, seldom leaving the tray, mat or paper on which they are placed, and where the females lay their eggs.

As regards the hatching of the eggs, it is important to know that this may be retarded as long as the owner pleases, by subjection to a low temperature; and it will be well for

those who purpose keeping silk-worms for the sake of profit, to defer the hatching of the eggs until the mulberry-trees are sufficiently forward to ensure a constant supply of food. The usual time for the hatching of silk-worms' eggs in this country is about the 12th of May, but a fortnight later is much better; for at that time the mulberry-trees have not generally put forth their leaves, and great difficulty continually occurs in procuring food: for, as far as we have yet learned, no other food than mulberry-leaves affords to silkworms wholesome nutriment; lettuce, dog-wood and blackcurrant leaves have been often tried, but without success.

It may be remarked that in winding off the silk, when the single threads of half a dozen cocoons are found, they may be guided with one hand on a small reel constructed for the purpose, which may be turned with the other hand, the cocoons at the same time floating on a basin of warm water.