To supply an establishment of the com mon kind, where 100 eggs are daily hatched, a dozen liens would be needed, and 150 eggs must be placed under them, as only two-thirds succeed ; at this rate 4500 mothers would be required to sit. In China the process is different. There the hatching house is a long shed with mud walls and thickly thatched with straw. Along the ends and down one side of the building are a number of round straw baskets, well plastered with mud, to prevent them from taking fire. In the bottom of each basket there is a tile placed ; or rather the tile forms the bottom of the basket. Upon this the fire aets—a small fireplace being below each basket. Upon the top of each basket there is a straw cover which fits closely, and is kept shut while the process is going on. In the centre of the shed are a number of large shelves placed one above another, upon which the eggs are laid at a certain stage of the process. When the eggs are bought they are put into the baskets—the fire is lighted below them—and a uniform heat kept up, rang ing from 95 to 102 degrees ; but the Chinamen regulate the heat by their own feelings, and therefore it will, of course, vary considerable. In four or five days after the eggs have been subject to this temperature, they are taken eareftdly out, one by one, to a door, in which a number of holes have been bored nearly the size of the eggs ; they are then held against these holes, and the Chinamen look through them, and are able to tell whether they are good or not. If good, they are taken back, and replaced in their former quarters ; if bad, they are, of course, ex cluded. In nine or ten days after this— that is, about fourteen days from com mencement—the eggs are taken from the basket, and spread out on the shelves. Here no fire-heat is applied, but they are covered over with cotton, and a kind of blanket, under which they remain about fourteen days more, when the young ducks burst their shells, and the she teems with life. These shelves are large and capable of holding many thousands of eggs; and when the hatching takes place, the sight is not a little curious. The natives who rear the young duck in the surrounding country know exactly the day when it will be ready for removal ; and in two days after the shell is burst, the whole of the little creatures are sold and conveyed to their new quarters. INDIGO. From the differences which exist in the nature and culture of the indigofera, and of its treatment by the manutheturer, the product, indigo, as found in commerce, differs remarkably in quality and chemical composition. Besides the impurities accidentally pre sent, from a bad season, want of skill or care, the purest commercial indigo con sists of no less than five constituents—I. Indigo-blue, a very singular vegetable compound of carbon, hydrogen, and oxy with about ten per cent. of azote; 2. Indigo-gluten, a yellow, or brownish yellow varnish, which difers from wheat gluten by its solubility in water. It has the taste of or of beef-soup, melts when heated, burns with flame, and affords an empyreumatic oil along with ammonia by distillation; 8. Indigo brown. This constituent is more abundant than the preceding. It is extracted by a concentrated water of potash, made to act on powdered indigo, previously di gested in dilute sulphuric acid. Chev • reuil's indigo-green seems to have con sisted of this substance, mixed with some alkaline matter, and indigo-blue • 4. In digo-red. This is readily dissolved by boiling alcohol out of indigo previously subjected to the action of an acid or alka line rnenstruum. The alcohol acquires a beautiful red tinge, and leaves by its evaporation the red principle in the form of a blaekish-brown varnish ; 5. Phos phate of lime. Dr. Ure found the bone phosphate in notable quantity in some fine indigo, constituting another feature of resemblance between this vegetable and animal products. Hence, also, the charcoal of indigo is most difficult of in cineration, and requires, for perfect com bustion, in some cases, the Ilangratory powers of nitric acid.
The species of indiggfera are legninin ous plants, herbaceous or shrubby. They
are very numerous in the equatorial re gions of the globe. The I. tinctoria is the species most abundantly cultivated. The plant requires a rich,light soil, and a warm exposure. It succeeds best on newly-eleared lands, on account of their moisture it requires protection against high winds, and needs Irrigation in times of drought. The ground, after being properly prepared for the reception of the seed by ploughing, is sown pretty thickly, the time of sowing being so chosen that rain may fall upon the plant as soon as it shows itself above the ground, by which it is not only greatly invigorated, but cleansed from innumer able insects.
As the plant approaches to maturity, the leaves undergo a sudden change in color, from a light to a dark green. As soon as this change is observed, the branches arc severed from the parent stem early in the morning, and spread out in the sun till the afternoon, by which time they become sufficiently dry to he beaten from the branches by a stick. The leaves, so separated, are housed in ware houses, closely packed and well trodden down by natives.
The plants, from which leaves have been severed, send forth a new crop, which is gathered, when mature, like the first. The cuttings, in a favorable sea son, are repeated three or four times, after which the ground is ploughed up for another sowing; but each successive growth of the branches produces an in creased deterioration of the qualities of the leaves, so that one part of the leaves of the first cutting yields as much indigo as two parts of the third crop. The dried leaves are not immediately used, but are kept packed for one month, during which time they suffer a material change, which is indicated by their having passed to a light lead color. By additional keeping, the lead color gradually darkens, until it becomes black. The maximum quantity of indigo is to be obtained when the lead color is attended with a loss in the quan tity of the indigo. The dried leaves, after having suffered the change of color, are transferred to the steeping-vat (an uncovered reservoir, 30 feet square, and 26 inches deep, constructed of brick, and lined with stucco,) where they are mingled with water, in the proportion of about one volume of leaves to six of water, and allowed to remain two hours.
The great affinity of indigo for oxygen is very manifest, in the quick change of the color of the leaves which float on the surface, and are exposed to the action of the atmosphere, to a blackish blue, when contrasted with those below, which re main unchanged. On this account, the vat is frequently stirred, so that the floating leaves may be immersed. After two hours' infusion, the water, which, from the solution of imperfectly-oxygen ized indigo, has acquired a fine green color, is allowed to run off from the leaves, through strainers, into the beat ing-vat, where it is agitated by the pad dles of 10 or 12 natives for about two hours, during which time the fine green liquor gradually darkens to a blackish blue. At this time, lime-water is thrown into the vat, and thoroughly agitated with the whole mass of fluid. The mass is then left to subside for the space of three hours, when the supernatant liquid, which is of a fine bright Madeira color, is withdrawn, by orifices in the vat at dif ferent heights. The indigo is then re moved to the covered part of the manu factory, where it is put on a straining cloth, and allowed to drain throughout the night. On the following morning it is transferred to a copper boiler, where it is mingled with a quantity of water, and raised to ebullition. The contents of the copper are retaken to the strainers, and the drained indigo is then divided into small portions, and each portion well worked by the hands of the natives, in order to free it from air-bubbles. It is then carritd to the pressing-boxes, which are usually square, and of sufficient depth to leave the cake about two inches and a quarter in thickness. By means of a powerful screw, the water is separated from the indigo ; the cakes are gradually dried in the shade, and thus rendered fit for exportation.