tity, when we reflect upon the brief period employed by so small a creature in its production. Surely it is unnecessary to call in the aid of exaggeration more highly to excite our wonder.

Miss Rhodes of Yorkshire found that one of her largest cocoons measured 404 yards. Pullein considers the average to be 300 yards. Miss Rhodes found that her cocoons weighed three grains each. Count Dandolo calculates the weight to be 3 grains, equal to about 3 English grains.

The size of an ordinary cocoon of good quality is about an inch in its largest diameter, and one third less in its smallest diameter. The largest diameter of dupions is an inch and a quarter, and their smallest diameter three quarters of an inch.

The attendance required for the care of silkworms does not wholly occupy the time of those employed, and it is, therefore, difficult to ascertain its amount with correctness. Pullein states, that for rearing the worms produced from six ounces of eggs two attendants are necessary until the fourth age, and that after this period five or six persons are required. Count Dandolo, with his accustomed accuracy, reduces the time required for attendance upon the produce of five ounces of eggs to an equality with one hundred days' continuous labor of one individual.

From these data it is found, that to obtain one pound of reeled silk it requires 12 pounds of cocoons; that rather more than 2800 worms are employed in forming these cocoons; and that to feed these during their caterpillar state, 152 pounds of mulberry leaves must be gathered. This pound of reeled silk is capable of being converted into sixteen yards of gros de Naples of ordinary quality, or into fourteen yards of the best description.

If

Experience has shown that some regulation of temperature is necessary in producing the moths from the cocoons. the heat in which these are placed be above 73°, their transition would be too rapid, and their productiveness would be lessened: on the other hand, if the temperature be below 66°, the development of the moths is tardy, and their produce equally falls below the due proportion.

The moths should begin to issue from their concealment in about fifteen days. The female deposits her eggs upon sheets of paper, or strips of linen, which are then hung in a cool situation, and when dry are preserved in an airy place, and securely shielded from damp and from vermin. making choice of a situation wherein to store these eggs for

In

the winter, although it is necessary to keep them cool, that premature hatching may be avoided, it is, on the other hand, indispensably requisite to preserve them from too intense a degree of cold: a temperature wherein water will freeze would be infallibly destructive of their vitality.

CHAP. VI.

DISEASES OF SILKWORMS.

General result from Bad Treatment.-Silkworms frequently reared in Cot. tages of Peasants.-Count Dandolo. His great Improvements.-Dandolières.-Mephitic Air.-Moisture.-Experiments.-Jaundice.-Remedy.-Chlorine Gas.-Chloride of Lime.-Fumigation.-Light not injuriousDescription of Apartments allotted to Silkworms in Cottages.-Ill Effects which arise to their Attendants.

THE silkworm is said to be subject to many diseases. There is reason for believing that most or all these are either the consequences of bad treatment, or are easily counteracted by simple remedies. Count Dandolo, to whose recorded experience reference has so often been made in these pages, was obliged to have recourse to other cultivators for the means of describing diseases that did not exist in his own establishment.

The custom which prevails in Italy and France of distributing silkworms to be reared in the dwellings of the peasantry has confined the management principally to the hands of ignorance and prejudice; and little or no improvement had in consequence been made in this part of rural economy until count Dandolo devoted himself to its reformation, and thereby promoted a branch of industry highly important to the prosperity of his native country. This nobleman pursued the occupation with patriotic and philosophic aims far different from such as usually characterize pursuits of business. He brought scientific knowledge and enlightened views to the subject, and afforded a clear exemplification of the fact, that there is no process, however simple, no employments, however humble, and which might apparently be consigned without injury to the hands of the untaught and unreflecting, that do not call for the head as well as the hand of man, to conduct them on rational principles, and to derive from them all the beneficial results they may be made capable of yielding. It is seldom that objects of profit are thus undertaken and pursued. It most generally happens, that toils of this nature are assumed from necessity, by per

sons who think only of rendering them subservient to the calls of that necessity; who have neither mind nor leisure for experiments; and who, if, by departing from the beaten track, they have made a greater proficiency than their rivals, are too prone to keep secret their discoveries with a view to individual advantage. Count Dandolo was not thus satisfied to find out and to pursue the most advantageous methods, but widely disseminated the knowledge of his mode of treatment, not only by his writings, but by inviting the great proprietors, his countrymen, to send pupils to him, who might obtain practical instruction in his methods. These pupils sometimes occasioned great losses to him, as in order to their acquiring the necessary degree of skill, they were sometimes allowed to act upon their own suggestions. "But this signifies little," he would say, "compared to the advantage of diffusing and naturalizing the improved art of rearing silkworms by means of these pupils." Shortly after the publication of his treatise, large establishments were formed in Lombardy, according to his recommendation: these were called Dandolières, as a testimony of respect for his disinterested philanthropy.

The causes which principally engender diseases in the silkworm appear to exist in either damp, stagnate, or mephitic air. Some experiments tried in order to ascertain the fact show that damp air is even more prejudicial to them than mephitic (carbonic acid) gas. If a silkworm be introduced into a receiver charged with carbonic acid gas, and in which a bird would instantly die, although the worm quickly exhibits signs of uneasiness and suffering, it will live for ten, fifteen, or perhaps twenty minutes; no warm-blooded animal could continue alive in such an atmosphere for half that time. If, after remaining a few minutes, the worm be withdrawn from the receiver, it will not exhibit any sign of injury, but will be, apparently, as healthy as before inhaling this pernicious gas. The silkworm appears endued with the power to seize upon the minutest portion of vital air which may be held by water, as it will live for some minutes immersed in this fluid, particularly in its first ages; and, even when seemingly dead, it will revive if taken out. It would seem, however, that when its power of breathing is obstructed, the worm instantly dies: if, instead of plunging it in carbonic acid gas, or in water, its eighteen breathing holes are sealed up with grease, it expires instantaneously.

If a healthy silkworm be confined in a vessel, the air in which is charged with moisture, and heated to the tempera

M

ture of 88° or 90°, it will very soon exhibit symptoms of indisposition, and reject food; the skin will slacken, the muscles soften, and contraction cease. In a short time evaporation will be obstructed, the secretions indispensable to vitality, which are effected in this animal by means of contraction,* will be suspended, and ere long it will perish. A warm-blooded animal, on the contrary, if sufficiently supplied with pure air, can live without any suffering, and perform all its functions without inconvenience, in such a temperature, whatever be the attendant degree of moisture. This proves how different is the structure of these two classes of animals.

In the southern departments of France, it is very common to see silkworms attacked by a disease which, in conse quence of the color assumed by them, is called the jaundice. Very careful examination is continually made for the discov ery and removal of worms which may be thus attacked, lest the disease, which is contagious, should spread to others. It is stated in the Bulletin Üniversel, that the abbé Eperic of Carpentras had recourse in this case to a remedy, or rather a preventive, which, though apparently dangerous, has been justified by the uniform success of twenty years. By means of a fine silk sieve he powdered his worms with quicklime, and after this gave them mulberry leaves moistened with a few drops of wine; these the insects instantly commenced devouring with an eagerness greater than that which they usually exhibited, and not one of the hurdles upon which the worms were thus treated ever appeared infected with jaundice. It was at first supposed that the cocoons might be injured by this process; but this is not the case, and the method is now very frequently adopted in the department of Vaucluse.

It is well known that decayed leaves emit mephitic air abundantly, and the lime may have been efficacious in absorbing and fixing this as it was generated, leaving the atmo sphere inhaled by the insects in a desirable state of purity.t

Mons. Blanchard records the following experiment, which satisfactorily proves the efficacy of the use of lime:-"I procured," he said, "four glass jars, nine inches deep and five in diameter, and provided them with cork stoppers. In each of these glasses I placed twelve silkworms at their second age;

*The skin of the silkworm has so great a power of contraction, that on being cut through it shrinks in the manner of an elastic substance that has been drawn out.

† Note A A..

these were fed four times a day, and I confined them in this kind of prison all their lives, without taking away either their dead companions or their litter. I sprinkled with lime the worms of only two of these jars, and kept the two others to compare with them. In those without lime, I never obtained more, or less than three, small and imperfect cocoons, and in the two that were sprinkled with lime I had very often twelve, and never less than nine fine full-sized firm cocoons. Mons. Blanchard ascertained, by many trials, that the worms were not incommoded when covered with a large portion of lime.

Count Dandolo advises fumigation with chlorine gas; but the mode of producing this from black oxide of manganese, common salt, and sulphuric acid, might be attended with unpleasant consequences, if intrusted to ignorant or careless hands, and to inhale the vapor as generated is not only unpleasant but dangerous, Chloride of lime, the use of which is attended with highly beneficial results as a disinfectant, and in neutralizing the pernicious effects of mephitic vapors, might prove advantageous in silkworm establishments, producing all the good effects of fumigation with chlorine gas, without hazarding any of the pernicious results which might accompany the latter application.

Among the peasants of France and Italy there is a practice of fumigating the room where the insects are kept with some kind of aromatic gum or odoriferous plant, but these only serve to conceal without correcting the effluvia which should warn the attendants of the necessity for cleanliness, and instead of removing increase the evil.

Many persons believe that light is injurious to silkworms ; but, so far from this opinion being correct, the opposite belief would probably be nearer to the truth. In its native state, the insect is of course exposed to light, and suffers no inconvenience on that account; and it has been observed by one who gave much attention to the subject, that in his establish. ment, "on the side on which the sun shone directly on the hurdles, the silkworms were more numerous and stronger than in those places where the edge of the wicker hurdle formed a shade." The obscurity wherein the apartments are usually kept has a very pernicious influence on the air: the food of the worms emits in light oxygen, or vital air, while in darkness it exhales carbonic acid gas, unfit for respiration. This well-known fact occurs alike with all leaves similarly gircumstanced,* To the bad effects thus arising from the *Note B B,