Page:The New Monthly Magazine - Volume 095.djvu/460

Rh shown by the observations of Mr. Warrington, of Apothecaries' Hall, as well as by his own made on the spot.

"The question presents itself, then," says Mr. Warrington, alluding to the variation of physical and chemical properties in green and black teas, "from whence do these distinguishing peculiarities arise, and to what are they to be attributed" From observations made in other directions, in the course of the routine work of the establishment to which I am attached, I had formed in my own mind certain conclusions on this subject. I allude to the exsiccation of medicinal herbs; these are for the most part nitrogenous plants, as the Atropa belladonna, the Hyosciamus niger, the Conium maculatum, and others. The plants are brought to us by the growers or collectors front the country, tied up in bundles, and when they arrive fresh and cool, they dry of a good bright-green colour; but on the contrary, it is found that if they are delayed in their transit, or remain in a confined state for too long a period, they become heated, from a species of spontaneous fermentation, and when loosened and spread open emit vapours, and are sensibly warm to the hand: when such plants are dried, the whole of the green colour is found to have been destroyed, and a red-brown and sometimes a blackish-brown result is obtained. I had also noticed that a clear infusion of such leaves evaporated carefully to dryness was not all undissolved by water, but left a quantity of brown oxidised extractive matter, to which the denomination Apothem has been applied by some chemists; a similar result is obtained by the evaporation of an infusion of black tea. The same action takes place by the exposure of the infusions of many vegetable substances to the oxidising influence of the atmosphere; they become darkened on the surface, and this gradually spreads through the solution, and on evaporation the same oxidised extractive matter will remain insoluble in water. Again, I had found that the green teas, when wetted and re-dried, with exposure to the air, were nearly as dark in colour as the ordinary black teas. From these observations, therefore, I was induced to believe that the peculiar characters and chemical differences which distinguish black tea from green were to be attributed to a species of heating or fermentation, accompanied with oxidation by exposure to the air, and not to its being submitted to a higher temperature in the process of drying, as had been generally concluded. My opinion was partly confirmed by ascertaining from parties conversant with the Chinese manufacture, that the leaves for the black teas were always allowed to remain exposed to the air in mass for some time before they were roasted."

Here, then, we have the matter fully and clearly explained; and, in truth, what Mr. Warrington observed in the laboratory of Apothecaries' Hall may be seen by every one who has a tree or bush in his garden. Mark the leaves which are blown from trees in early autumn; they are brown, or perhaps of a dullish green, when they fall, and yet, if they are examined some time afterwards, when they have been exposed to air and moisture in their detached state, they will be found quite as black as our blackest teas.

I must now make some observations upon the tea-plant itself. It has already been remarked that two tea-plants, considered to be distinct varieties, are met with in China, both of which have been imported into Europe. One, the Canton variety, is called Thea bohea; the other, the northern variety, is called Thea viridis. The former produces the inferior green and black teas which are made about Canton, and from the latter are made all the fine green teas in the great Hwuy-chow country and in the adjoining provinces. Until a a [sic] few years back it was generally supposed that the fine black teas of the Bohea hills were also made from the Canton variety, and hence its name. Such, however, is not the case.

When I visited Foo-chow-foo for the first time in 1845, I observed that the tea-plant in cultivation in that neighbourhood was very different from the Canton variety, and apparently identical with the Thea viridis of Chekiang.