The History of Silk, Cotton, Linen, Wool, and Other Fibrous Substances; / Including Observations on Spinning, Dyeing, and Weaving.

by Clinton G. Gilroy

These processes appear efficacious for checking the hatching, until the expanding leaves of the mulberry-tree give notice to the silk-worm-rearer that he may take measures for bringing forth his brood. For this purpose the rolls of paper are taken from the earthen vessels, and hung up towards the sun, the side to which the eggs adhere being turned from its rays, by being placed inside, and thus allowing the heat to be transmitted to them through the paper. In the evening the sheets are rolled closely up and placed in a warm situation. The same proceeding is repeated on the following day, when the eggs assume a grayish color. On the evening of the third day, after a similar exposure, they are found to be of a much darker color, nearly approaching to black; and the following morning, on the paper being unrolled, they are covered with worms. In the higher latitudes the Chinese have recourse to the heat of stoves, in order to promote the simultaneous hatching of the eggs.

The apartments in which the worms are kept stand in dry situations, in a pure atmosphere, and apart from all noise, which is thought to be annoying to the worms, especially when they are young. The rooms are made very close, but adequate means of ventilation provided: the doors being open to the south. Each chamber is provided with nine or ten rows of frames, placed one above the other. On these frames, rush hurdles are ranged; upon which the worms are fed through their five ages. A uniform degree of heat is constantly preserved, either by means of stoves placed in the corners of the apartments, or by chafing-dishes which from time to time are carried up and down the room. Flame and smoke being always carefully avoided: cow-dung dried in the sun is preferred by the Chinese to all other kinds of fuel for this purpose.

The most unremitting attention is paid to the wants of the worms, which are fed night and day. On their being hatched they are furnished with forty meals for the first day, thirty are given on the second day, and fewer on and after the third. The Chinese believe that the growth of silk-worms is accelerated, and their success promoted by the abundance of their food, and therefore, in cloudy and damp weather, when the insects are injuriously affected by the state of the atmosphere, their appetites are stimulated by a wisp of very dry straw being lighted and held over them, thus causing the cold and damp air to be dissipated.

The Chinese calculate that the same number of insects which would, if they had attained the full size in twenty-three or twenty-four days, produce twenty-five ounces of silk, would give only twenty ounces if their growth occupied twenty-eight days, and only ten ounces if forty days. In order, therefore, to accelerate their growth, they supply them with fresh food every half-hour during the first day of their existence, and then gradually reduce the number of meals as the worms grow older. It deserves to be remarked as a fact unnoticed in Natural Theology, that the substance on which this valuable caterpillar feeds, is the leaf of the mulberry-tree; and Providence, as if to ensure the continuance of this useful species, has so ordained it that no other insect will partake of the same food; thus ensuring a certain supply for the little spinster.

Many persons believe that light is injurious to silk-worms; 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 (Count Dandolo), that in his establishment, “on the side on which the sun shone directly on the hurdles, the silk-worms were stronger and more numerous 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 circumstanced[138]. To the bad effects thus arising from the exclusion of the sun’s rays, another evil is added by the nature of the artificial lights employed, being such as still further to vitiate the air.

[138] “There is in the order of nature a certain, and very surprising fact; when the leaves of vegetables are struck by the sun’s rays, they exhale an immense quantity of vital air necessary to the life of animals, and which they consume by respiration.

“These same leaves in the shade as well as in darkness exhale an immense quantity of mephitic or fixed air, which cannot be inhaled without destruction of life.

“This influence of the sun does not cease even when the leaf has been recently gathered; on the contrary, in darkness, gathered leaves will exhale a still greater quantity of mephitic air.

“Place one ounce of fresh mulberry leaves in a wide-necked bottle of the size of a Paris pint, containing two pounds of liquid; expose this bottle to the sun; about an hour afterwards, according to the intensity of the sun, reverse the bottle and introduce a lighted taper in it; this done, the light will become brighter, whiter, and larger, which proves that the vital air contained in the bottle has increased by that which has disengaged itself from the leaves: to demonstrate this phenomenon more clearly, a taper may be put in a similar bottle, that only contains the air which has entered into it by its being uncorked. Shortly after the first experiment, water will be found in the bottle which contained the mulberry leaves; this water, evaporating from the leaves by means of the heat, hangs on the sides, and runs to the bottom when cooling; the leaves appear more or less withered and dry according to the liquid they have lost. In another similar bottle place an ounce of leaves, and cork it exactly like the former; place it in obscurity, either in a box, or wrap it in cloths, in short, so as totally to exclude light; about two hours after, open the bottle, and put either a lighted taper or a small bird into it; the candle will go out, and the bird will perish, as if they had been plunged into water, which demonstrates that in darkness the leaves have exhaled mephitic air, while in the sun they exhaled vital air”.—Count Dandolo’s Treatise on the Art of Rearing Silk-worms, p. 144.

An almost incredible quantity of fluid is constantly disengaged by evaporation from the bodies of the insects; and if means be not taken to disperse this as it is produced, another cause of unwholesomeness in the air arises. Noticing this, Count Dandolo observes, “This series of causes of the deterioration of the air which the worms must inhale, may be termed a continual conspiracy against their health and life; and their resisting it, and living throughout shows them to have great strength of constitution.”