Chinese colour was first met with as a sediment left after dyeing cotton cloths with the barks of Rhamnus chlorophorus and R. utilis, and known in China as Lo-Kao. The sedi ment is spread on blotting-paper, and dried, forming thin scales. It was highly valued, as affording a pure green even in artificial light. Its value in the London market, in 1861, was placed at 7s. 6d. an oz. In 1853, it was largely imported into France, for silk-dyeing. Iu 1864, Charvin obtained the same colouring matter from B. catharticus, a weed indigenous to Europe, and was able to sell it at 37s. a lb. These beautiful dye-stuffs are now completely driven from the market by the aniline dyes. (See p. 668.) Cochineal (FR., Cochenille e GER., Cochenille).—The colouring matter known as " cochineal " is the product of an insect called Coccus cacti, which lives on several species of cactus, but especially Cactus Hopal (Opunta coccinidifera). The plant and insect are natives of Mexico and Guatemala, but have been successfully introduced into the Canary Islands, as well as Algeria, Java, and Australia. The production is almost confined to Guatemala and the Canaries.
In the former country, gardens of the nopal plant extend in every direction. Each is surrounded by a mud fence, on which is built a thatched roof, forming a shed, which is open on the sunny aide. Here the insects are preserved and bred ; the young are placed in little leaf boxes or bags, attached to the spikes on the leaves of the plant. Rain is fatal to the insect, especially during the first ten days of its existence. According to Boddam-Whetham, in some districts, the female is left on the leaf long enough to produce a second crop in the same year ; this is much heavier than the first, and much more profitable. The gathered insects are spread on flat trays, covered with thin cloths, and placed in ovens. When dry, they are sifted, packed in bales, and sent to market.
Tho average yield of an acre of nopal is said to be about 1800 lb. of the insects in the two crops. In Mexico, tho plant and insect occur both wild and cultivated : the product from the cultivated plant is much superior, and is known as nustique ; that from the wild plant is called sylvestra. In May, in the plains, and in November, in the hills, the Indians remove the young female insects to growing plants ; after about three months, the myriads of young insects borne by the female aro brushed off the leaves into tin dishes. They are then thrown into hot water, and dried in the sun or in stoves, producing zacatilia, or "black cochineal" ; or they are bagged or stoved at once, whioh process leaves them with a peculiar lustrous look, whence they are termed blanco, or " silver coohi neal." The values of the New World brands distinguished in the London market are approxi mately as follow :—Hondurae, black, 2s.-2e. 5d. a lb.; silver, 28.-28. 3d. ; Mexican, black, 2s. ld. ; silver, ls. lOd.-le. 11d. The exports (in quintals of 101i lb.) from Guatemala, in 1878, were i—to California, 155 ; England, 133 ; New York, 70 ; S. America, 54. The total value was about 45001. ;
in 1877, it was 36,0001. Less than twenty years ago, the exports amounted to 600-750 tons yearly.
The cultivation in the Canaries is carried on as follows :—The insects are reared in the winter, so as to be ready for " planting," or putting out on the cactus plants, in the latter end of May to late July or early August. The plants are robbed of their fruit as fast as the buds appear, other wise they become too weak for rearing the cochineal insects. About a table-spoonful of pregnant females are put into little gauze bags, 8-9 in. long, and hung upon the cactus leaves. The young escape as fast as they are born, and spread over the surface of the leaf, great care being required to proportion the number of insects to the size of the leaf. In August and September, the moment the insects exhibit signs of spawning, they are rapidly collected. The method of gathering them varies much, but, as a rulo, the leaves holding bags aro severed sharply by a knife, close to the branches, and the cochineal is swept off into closely-woven, broad baskets. The leaves are after wards cut up, and dug in between the rows, as manure. Other hands carefully scrape off any insects which may have passed into the breathes or stem of the plant, as these would otherwise spawn, and weaken the plant, to the injury of future crops. Immediately the insects arc gathered, they should be turned out of the baskets, and spread in a layer not exceeding 2-3 in. in depth, either on trays, or on a sheet on the ground. Here the cochineal remains during the day. Towards evening, it is placed in an oven, heated to about 65° (150° F.), for four to five hours ; the oven is then allowed to cool gradually till the morning. When taken out, the insects will be found still moist ; they are then exposed to the sun for a few days to complete the drying, suffering much less loss of weight in this way than if they were thoroughly dried in the oven. A few growers use special means to effect the drying :—(1) A little wood ashes is scattered over the cochineal ; the latter dies in an hour or two; the dust is sifted off, and the cochineal is dried in the sun. (2) Moderate quantities of the insects) are placed in a sack, which is violently shaken ; this produces a brilliant polish, which enhances the price of the article sufficiently to atone for the slight loss of weight incurred. The oven is, however, most universally employed. The "grain," as the dry cochi neal is Galled, is sifted, to remove an adherent white powder, and is picked over, to free it from fragments of the plant. When clean, it is packed in bags of about 150 lb. each, for export. The produce is estimated at 250 lb. dry oochineal from an acre. Hot winds from the Sahara, and heavy rain, are fatal to the crop. Compared with the American article, the London prices of Teneriffe cochineal are about as follow :—Blaok, 2s.-2s. 10d. a lb.; silver, 2s.-2s. ld.