TAWING. The art of preparing cer tain kinds of leather by imbuing the skins with saline, oily, and other mat ters. (See TANNING.) TEA. The leaves of the Thea This plant resembles the Caineilia, but its leaves and flowers are much smaller. It is five or six thct high, and is an ever green. It is a native of China and Japan, and has been cultivated there for centuries ; was unknown in Europe till the middle of the seventeenth century, yet is now become of so much import ance as to employ 50.000 tons of shipping in its transportation from Canton. It is cultivated in all parts of Chin.. ;VIM at Pekin, which has the same latitude as Philadelphia. The plants require little care till the third year, when they are fit for gathering. In seven years the plants attain the height of six feet. The leaves are plucked off one by one with many precautions, and from six to sixteen pounds per day are plucked. The first leaves are gathered at the end of the winter, when the leaves are young and tender; the second gathering is in the beginning of spring, when the leaves are of nearly their full size ; the last gather ing takes place in midsummer. These are of inferior quality. There are two varieties of tea—the That viridie and Thea bohea. Formerly it was believed that all the green tea was gathered from T. vi•idis, but this is now known not to be so, there being a green tea district where the leaves are gathered from both varieties of trees indiscriminately. The names given in commerce are unknown to the Chinese. When the leaves are gathered they are dried in houses con taining small furnaces, having an iron pan on the top of each. The leaves are rolled on tables covered with mats, and then a few pounds are laid on the iron pan heated ; the Workman shifts them with his bare hands lest they should burn. When lie cannot bear the heat longer he transfers the tea to the mats ; they are then rolled again on the pan till they are twisted : it is repeated fre quently before the tea is so that no moisture may remain in it. Ile dd..
ferent kinds of black and green differ not only in soil and climate but in after treatment. The color of green tea is due to an admixture of gypsum and Prussian blue, which is dusted over it in the pans.
The leaves of tea have little or no smell, and they derive their fragrance by mixing the leaves of Olea fraqrans and Camellia sesanqua, also of Polegalo the zuns, and of.Rhamnus thezans.
China tea does not turn black by wa ter, impregnated with sulphuretted hy drogen 4as ; nor give a blue tinge to spirit of hartehorn. The infusion, amber colored, is not reddened by sulphuric acid. The leaves, separate or mixed, of speedwell, wild germander, black cur rants, mock orange, purple-spiked wil low herb, sweet-briar, cherry-tree, haw thorn, bramble, sloe, are substituted for tea by dealers. Foreigners use a variety of plants, instead of Chinese tea, and Zenoponuithea Sinensis is cultivated in France as a substitute. Japanese camellia leaves are frequently, by the Chinese, mixed with those of tea.
Russian tea, is leaves of saxifrage, winter green, white virgin's bower, bird cherry, drop worts, common elm, male fern, and dog-rose.
The active principle of tea is believed to be Theine, a substance found also in coffee and in the ile.v paraguyaensis, a native of Brazil.
Mr. Stenhouse prepares theine by pre cipitating a decoction of tea with solu tion of acetate of lead, evaporating the Altered liquor to a dry extract, and posing this extract to a subliming heat in a shallow iron pan, whose mouth is covered flatly with porous paper ]rated round the edges, as a filter to the vapor, and surmounted with a cap of compact paper, ss a receiver to the crystals. In this way lie obtained, at a maximum, only P37 from 100*00 of tea. But M. Peligot, from the quantity of azote amounting to about 6 per cent., which lie found in the tea leaves, being led to believe that much more theine existed in them than bad hitherto been obtained, adopted the following improved process of extraction. To the hot infusion of tea, subacetate of lead and then ammonia were added ; through the filtered liquor a current of snlphuretted hydrogen was passed to throw down all the lead, and the clear liquid being evaporated at a gentle heat afforded, on cooling, an abundant crop of crystals. By re-evapo ration of the mother liquor, more crys tals were procured, amounting altogethm to from 5 to 6 out of 100 of tea.