"Tea dust" affords a high proportion of ash, sometimes amounting to 20 per cent., the composition of which is usually strikingly different from that of the ash of ordinary tea. It is deficient in potassa and phosphoric acid, and the amount of ash insoluble in water and acids is very excessive, as is shown by the following analysis, made by the author:

The portion of ash insoluble in acids consisted of silica, clay, and soapstone, indicating that the ash of tea dust is largely composed of the mineral substances employed for "facing" purposes.

The characteristics of the ash of unspent tea are the presence of manganic oxide, the large proportion of potassium salts present, and the solubility of the ash in water. The amount of ash in genuine tea ranges from five to six per cent. In the absence of exhausted leaves, it has been found that the finer sorts of tea afford a smaller proportion of ash than the inferior grades. It will be noticed that spent tea ash exhibits a marked increase in the proportion of insoluble compounds (silica, alumina, and ferric oxide), as well as a total absence of potassium salts.

The presence of foreign leaves, and, in some instances, of mineral adulterants in tea is best detected by means of a microscopical examination of the suspected sample. The genuine tea-leaf is characterised by its peculiar serrations and venations. Its border exhibits serrations which stop a little short of the stalk, while the venations extend from the central rib, nearly parallel to one another, but turn just before reaching the border of the leaf.

Plate I. (Frontispiece) is a photogravure of a twig of the tea plant, in possession of the author. The leaves are of natural size, but the majority are of a greater maturity than those used in the preparation of tea, which more resemble in size the few upper leaves.

Plate II. shows more distinctly the serrations and venations of the tea-leaf. The Chinese are said to occasionally employ ash, camelia, and dog-rose leaves for admixture with tea, and the product is stated to have formerly been subjected in England to the addition of sloe, willow, beech, hawthorn, oak, etc. For scenting purposes, chulan flowers, rose, jasmine, and orange leaves, have been employed. The writer has lately received from Japan specimens of

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willow, wisteria, te-mo-ki, and other leaves which at one time were used in that country as admixtures.

Plate III. exhibits some of these leaves, two genuine Japan tea-leaves being included for purpose of comparison. The leaves represented in this plate are: 1, beech; 2, hawthorn; 3, rose; 4, Japan tea; 5, willow; 6, te-mo-ki; 7, elm; 8, wisteria; 9, poplar. From very recent reports of the American consuls in Japan and China, it would appear that the addition of foreign leaves to tea is at present but seldom resorted to, and this accords with the author's experience in the testing of the teas imported into this country.

In 1884, the Japanese Government made it a criminal offence to adulterate tea, and instituted "tea guilds," which are governed by very stringent laws, and of which most dealers of repute are members. The facing of tea does not appear, however, to have been considered an adulteration, its continued practice being justified by the plea that otherwise Japan teas would not suit the taste of American consumers.

In the microscopic examination of tea, the sample should be moistened with hot water and spread out on a glass plate, and then submitted to a careful inspection, especial attention being directed to the general outline of the leaf and its serrations and venations. The presence of exhausted tea-leaves may often be detected by their soft texture and generally disintegrated appearance. If a considerable quantity of the tea be placed in a long glass cylinder and agitated with cold water, the colouring and other abnormal substances frequently become detached, and either rise to the surface of the liquid as a sort of scum, or fall to the bottom as a sediment. In this way Prussian blue, indigo, soapstone, gypsum, sand, and turmeric can often be separated, and subsequently recognised by their characteristic appearance under the microscope. The separated substances should also be subjected