BLACK TEAS.—Chinese: (1). Congo sorts—viz., Canton, Foo-chow-foo, Hung-muey, Oopaek, Kaison, and Oonam; (2) Pekoe sorts—viz., plain orange, Foochow, scented orange, Canton scented orange, and flowery Pekoe, Oolong, and Souchong. Assam: Congo, orange Pekoe, and Souchong. Java: Congo and imperial. The latter is made up into little balls about the size of a pea, and is rare.
The use of the infusion of the leaves of tea as a beverage is general in the s.e. parts of Asia, and has become prevalent also amongst the British—at home and in all their colonies—the Americans, and the Dutch. In Scandinavia, tea is also much used by all who can afford it. In other parts of Europe the use of tea is much less general, and is chiefly confined to maritime districts, towns, and the wealthy. The importation of tea overland through Russia is inconsiderable, and the sea trade is chiefly to Britain and North America.
The substitutes for tea, in countries where it is difficult to obtain it, are of two sorts: those which contain theine, and which consequently have the same stimulating effect; and those which are destitute of that principle, and only resemble the true tea in fla vor or smell, or which possess some other stimulating principle. Of the former class are—(1). Mate (q.v.); (2). Guarana (q.v.)—so rich is this material in theMe that it has lately been used in this country for obtaining that principle; and it has been intro duced into Austria and France as a powerful medicine; (3). Coffee-leaves, which, are occasionally prepared as a substitute in the West Indies; they would be more gener ally used were it not for the disagreeable smell of the infusion; (4). the kola-nut, the active principle of which was some years ago ascertained to be theine.* The second class, or those which do not possess that principal, are very numerous; but only a few can be said to be of any importance from being in general use in the countries producing them. These are the Siberian tea—leaves of saxifraga crassifolia; the Appalachian tea—leaves of prinos glabra; the Labrador tea—leaves of ledum buxi folium; the Chilian tea—leaves of Eugenia uyni; Trinidad pimento tea—leaves of and the leaves of the partridge-berry, which are used in some parts of North America. The Faham tea of Mauritius, and a great many more, should be re garded in the light of medicines rather than as ordinary beverages, although they are generally classed as substitutes for ordinary tea.
Tea, in its chemical, physiological, and medicinal submitting the ordi nary commercial teat to analysis, we find that it contains (1) a volatile or essential oil; (2) theine or caffeine, described in this work under the latter name; (3) a nitrogenous compound analogous to caseine or gluten; (4) a modification of tannin; besides gum, sugar, starch, fat, woody fiber, salts, etc. The 'volatile oil gives to tea its peculiar aroma and flavor. The proportion iu which it exists is, according to Miller, about 0.79 per cent in green, and 0.6 per cent in black tea. It may be obtained by distilling the tea with water, and is found to exert a most powerfully stimulatina. and intoxicating effect. In China tea is seldom used until it is a year old, on account of the well-known intoxica ting effects of new tea, due probably to the larger proportion of essential oil which it usually contains. The headache and giddiness of which tea-tasters complain, and the attacks of paralysis to which, after a few years, persons employed in packing tea are found to be liable, are due to the action of this oil, which according to Johnston, "does not exist in the natural leaf, but is produced during the process of drying and roasting." Chemistry of Common Life, 1855, vol. i. p. 170.
The theine or caffeine, an alkaloid of weak basic properties, varies considerably in dif ferent kinds of tea. Peligot found it to range from 2.2 to 4.1 per cent in ordinary
green teas, while very rarely it amounted to 6 per cent; whereas from the researches of Stcnhouse it appears that not more than 2 per cent is usually contained in the ordinary teas in the English market. It may readily be obtained by the following simple experi ment. When dry finely-powdered tea leaves, or a dried watery extract of the leaves, arc put on a watch-glass covered with a paper cone, and the whole is placed upon a hot plate, or exposed to the heat of a spirit-lamp, a white vapor gradually rises and condenses on the interior of the cone, in the form of small crystals, which consist of theine. As it has no odor, and only a slightly bitter taste, it obviously has little to do with the taste or flavor of the tea from which it is extracted; it is, however, to the presence of this ingredient that the peculiar physiological action of tea on the animal economy is due. This substance is represented by the formula Cie1ioN40.± 2Aq, and is remarkable for the large quantity of nitrogen (28.83 per cent) which it contains, and which is nearly * Dr. Daniell's observations on the kola-nut (see the article COLA-NIIT) are of such Importance as to demand a notice here. From time immemorial the seeds of the kola-nut have been held in ines timable value as a luxury by the inhabitants of the vast tract between the west coast and the region of Central Africa known as Sudan; and the trade in these nuts has extended to various markets on the Mediterranean. The Portuguese, Dutch, and subsequently the English voyagers, fell into the negro predilections for this fruit; and eventually the due gratification of this want became a matter of imperative necessity. Dr. Daniell's knowledge of the tonic and astringent properties of these nuts was gained during his residence on the Gold Coast, where the white inhabitants were in the habit of taking a decoction of the fresh nuts, with apparent benefit, in a particular form of endemic diarrhea, arising more from local relaxation of the mucous membranes than from constitutional debility. On taking the medicine late, two evenings in succession, when he was afterward suffering from an attack of this kind in Jamaica, he found that he was deprived of sleep during the remainder of the night. On intermitting the decoction, the natural rest returned, and on returning to it, the insomnia again occurred. Hence he was led to suspect that a substance analogous to theine must be present; and a chemical analysis of the nuts yielded crystals in all respects resembling those of theme, and subsequently proved by the more careful investigations of Dr. Atfield to be composed of that alka loid. 'Wherever the slave-trade prevailed, the tree yielding the kola-nut (cola acuminata of Robert Brown) followed as a matter of necessity, being imported and cultivated for the benefit of the negro. It was thus introduced into the Mauritius, Jamaica, and other West India islands, Brazil, Mexico, etc, It was specially intended to act in warding off the predisposition to epidemic outbreaks of suicidal mania, which not unfrequently almost depopulated considerable districts. While Dr. Daniell's expel'. iments disprove the statement (alluded to in the article Cobe-Nirr) that these seeds render bad water palatable, his investigations, confirmed as they are by Dr. Atfield's chemical analysis, show, that whatever may be their food-value (which Dr. Daniell estimates higher, from his observations, than Dr. Atfield from their analysis), they may be advantageously substituted for coffee. See the papers by Dr. Daniell, " On the Kola-nut of Tropical West Africa," and by Dr. Atfield, " On the Food value of the Kola-nut," in the Pharmaceutical Journal for March, 1865.