indigos seldom attain 65-66 per cent. of indigotine; and their ash averages about 16½ per cent. The Philippines produce considerable quantities of indigo, the best coming from Luzon. The plants suffer from locusts and storms, but the cultivation is very profitable. The yield of indigotine is large, but the preparation is conducted in such a primitive manner that the value of the product is much deteriorated. In many parts of Africa, as Sierra Leone, Liberia, Abeokuta, the Niger valley, Natal, Cape Colony, Tunis, and the Soudan, species of indigo plants are found in a wild state, and from them the natives prepare an inferior dye-stuff. In some of the S. States of America, notably S. Carolina, indigo culture has been attended with more or less success. The method of preparation pursued here varies but very slightly from the ordinary Indian process, almost the only important modification being the addition of a little oil to the liquor in the beating-vat, when the fermentation becomes too violent. The precipitated fecula is placed in coarse linen bags, and hung up to drain. The drying is finished by turning it out of the bags upon a floor of porous timber, and working it up. It is frequently exposed to the sun for short periods at morning and evening, and is then placed in boxes or frames, to cure till it is fit for the market. Several of the Central American States have figured conspicuously as indigo producers. The dye is precipitated in the beating-vat by the sap contained in the bark of Tihuilate (_Yonidium_), Platanillo (_Myrosma Indica_), or Cuaja tinta. The fecula is left during the night; and, on the following day, is boiled, filtered, pressed, and sun-dried. In most districts, the cultivation is declining, partly owing to the carelessness exhibited in the preparation of the dye. Indigo is judged commercially by its lightness, by a copper gloss on the surface, and by exhibiting no foreign ingredients when broken. There are several ways of testing it chemically, to ascertain the exact proportion of indigotine present; one method is as follows:--Finely pulverised indigo, 1 part; green copperas, 2 parts; and water containing 10 per cent. of caustic soda, 200 parts; are well boiled in a flask, and left to cool. The clear liquor is exposed in shallow vessels to the air, when the soluble indigo is oxidised, and precipitated as pure indigotine. The residue in the flask is thus treated three times; the whole indigotine is then collected on a filter, dried, and weighed. The consumption of indigo is still very large. Artificial indigo has not, as yet, been manufactured on a commercial scale, nor at a commercial price; but it has been produced, in the laboratory, from coal-tar derivatives, and further experiment may reveal a process for preparing the article at a sufficiently low price to compete with the natural colour.