IDENTITY OF BLACK AND GREEN TEA.
Green and Black Tea are produced from the same plant, though the botanists were long at issue about this matter. The idea of green tea being dried upon copper is proved to be a popular fallacy, for the tea would be flavoured and spoiled in the process; besides, the bloom can be given by harmless means. Dr. Lettsom, by the way, thought it was given by a vegetable process.
Mr. Ball, who has written a practical volume on "the Cultivation and Manufacture of Tea," describes an experiment made by him, proving that tea may be dried black and green, at once, in the same vessel and over the same fire: he divided the pan, and the leaves on one side he kept in motion, and the other quiet—when the latter became black, and the former green; thus proving the difference of colour to be not derived from any management of heat, but from manipulation, the heat being the same in both cases.
At the same time, certain Chinese rogues glaze our hysons most unscrupulously; and it has been proved by chemical analysis, that the Chinese green teas are artificially coloured, though not with indigo, as represented by the green tea merchants. We may add, that gunpowder tea is dried at the highest temperature, and pekoe at the lowest; and the chemical cause of black tea is its loss of tannin in its drying, previous to roasting, an opinion that is supported by the testimony of Liebig. Again, Mr. Ball thinks there may be one species of tea plant, but several varieties, and that all botanical difference is destroyed in the course of packing.
PROTECTION BY RUST.
Rust is usually associated with decay. Professor Faraday, however, observes that, in some cases, it is curious to see how tin, a metal having a slight attraction for oxygen, protects other metals from oxidation or rust. In Canada, tin-plate is used for the roofs of houses, and you are dazzled by the lustre of the setting sun upon the roofs; whilst there, although it is exposed to the atmosphere year after year, it does not decay, because the superficial coat of oxide protects the tin and iron beneath.